ElectricMotorcycleForum.com
Tech => Home Brew => Topic started by: 3DRoboGuy on May 05, 2019, 04:56:21 PM
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Hi,
First time on the forum, so introductions first :
my name's Ian.
I'm an electrical/electronic engineer to trade and am reasonably handy.
I now live in France where nearly all the 14+ year-olds ride a 50cc petrol bike / scooter - least-ways my son and all his mates do ! Man, they're noisy, stinky, leaky and almost always needing repaired - the scooters, I mean !
After a bit of googling for some parts one day, I became distracted by emission control regs, scooters being banned from cities or charged for daily access to them... It seems that many thousands of older 'dirty' 50cc petrol scooters are facing premature scrapping (Netherlands / France) due to their age and the fact they are considered 'dirty'.
I'm pretty passionate (in a calm and resigned way, I think) about the planet, weather changes, greenhouse gas / small partical emissions and started to think of how I could make my son's (and his mates') scooters more eco- (and noise) friendly.
Anyways, I need a project and thought I'd convert one to electric.
I already have the scooter : 50cc chinese in good nick but with an annoying oil leak and intermittent spark problem.
My thoughts so far :
a 3Kw mid-mount AC or BLDC motor and compatible controller
a 72V LiPo battery pack - 20S8P (2Kw - can add to this later if required)
a small 12V LiPo battery pack for ignition / start-up etc
a 72/12V converter to charging the 12V LiPo pack and supplying lights and horn etc
a pair of SSR contactor(s) - 1 hi-voltage (72V) and 1 x lo-voltage (12V)
a similar acceleration & top speed (better if poss. but no worse)
20Km+ range / autonomy (with the internal 2Kw pack)
an onboard charger (4 to 5 hour charge period)
provision for an additional 2Kw of LiPo (increase range to around 40Km)
I intend to keep chassis / original equipment mods to a bare minimum - except the switch from ICE to electric and I'd like to think that as many decisions as possible will be based upon maintaining DIY simplicity / transfer to other makes of scooter. I don't really know the implications re: re-licencing / MOT / TuV but believe it to be pretty simple (having spoken to the DVLA) in the UK. In France, it's most impossible (currently) but everyone 'upgrades' their 50cc 'scoots' and no-one blinks an eye. No idea about the Netherlands and further afield.
The 'donor' scooter is to be the 'el-cheapo' Chinese RPS scooter in great nick, the parts could always be sold on - if I can find a buyer.
I'd like to think that 800 - 1000 Euro would do the trick. Considering the current London ULEZ charges (12£50/day) this would equate to a 3 - 4 month (5 days a week) reclaim period... seems pretty reasonable IF it can be done...
I'm thinking of documenting the whole project with a view to enabling others to copy... I'm most deffinitely not a You-Tuber but I could update the forum with progress and even make a website for posterity ;)
Does this sound feasible ? Any ideas / advice / thoughts ?
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I have wondered about this myself. Small scooters have considerable volume inside with fuel tank removed. Replacing the engine/transmission unit may be easier than adapting the existing part. I will be interested to follow your progress.
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Count me interested, Ian !!
Simplicity, Reliability, and the rewards of electric power are worth this conversion.
I like the values, beliefs, and hopeful outcomes expressed in your original post, and am very interested to follow along.
;)
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Hi Bill822 and MotoRyder.
Thanks for the encouragement. Whilst I find the conversions 'grips' me with all its little challenges etc I'm not (normally) one for writing to forums / websites and social media, so I'm trying it out with this project.
Here's the scoot as it arrived.
I ordered the motor / controller over the weekend and have stripped most of the ICE kit off / out of the scoot ready for me to 'play' about with battery, motor, controller (and other smaller item) placement.
I'll take some pics and put them up later.
Again, thanks both; its great to see others interested in the idea. If you have any pearls of wisdom you'd like to share I'd be only too happy to hear them. Like I say, I live in France, am Welsh by birth and although speak conversational French reasonably well / passably, I struggle to find others both interested and with whom I can discuss technical things easily. Hence my thoughts towards trying the forum.
Anyways...
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Cute scoot. :)
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Thanks Richard230,
The scoot's all stripped down now and ready for 're-fitting'.
I'll post up some pics later on.
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Great project and totally doable.
I previously worked for a company called Scoot. They do smart phone activated scooter sharing. The first 300 bikes in the fleet were Chinese manufactured electric scooters similar to what you have (image of the Scoots below)
https://techcrunch.com/2012/09/26/scoot-sf-launch/ (https://techcrunch.com/2012/09/26/scoot-sf-launch/)
We upgraded the bikes stock components with more reliable higher quality and performance pieces.
They ran a 1.8 kWh LiFePo4 batter in an 48v arrangement
The ran a hub motor (best option for lower power vehicles)
The ran a ASI3000 motor controller
As the bikes were classified as "mopeds" in the US they were governed by legal limitations of 4hp and 30mph (48kph) top speed. They were pretty zippy bikes quicker off the line than a 50cc 2 stroke. With that battery configuration we were seeing about 25 miles of range (40km).
There should be tons of room under the seat for the battey pack and the controller you decide to go with. As your bike uses the motor and transmission as the swingarm you will need to replace this with a different unit. The swingarms from our scoots were a simple H pattern made of steel. Should be easy enough to source or fabricate.
Good luck with the project!
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Thanks Demoni,
I was hoping to utilise the existing swingarm simply because I would prefer to keep the scoot as 'standard' as possible.
The 'downside' with this approach will be how to 'handle' the inbuilt 14:1 (or thereabouts) reductio(http://)n gearbox that is integral to the rear end of said swingarm. The upside is that the (rear) wheel and internal drum brake will remain totally standard.
Well... that's the idea at the moment
Here are the pictures I was talking about last week - I'm a little further advanced in these...
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Wow. Really not much to it once the body is off.
Using the reduction gearing would allow a lower torque motor (at higher RPM, of course), but cost a little mechanical efficiency. Will be interesting to see what fits.
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I was hoping to utilize the existing swingarm simply because I would prefer to keep the scoot as 'standard' as possible.
Totally understandable. I was just suggesting a hub motor because it would probably be the easiest solution besides the new swingarm.
The 'downside' with this approach will be how to 'handle' the inbuilt 14:1 (or thereabouts) reduction gearbox that is integral to the rear end of said swingarm. The upside is that the (rear) wheel and internal drum brake will remain totally standard.
So the reduction opens you up to other options for a drive motor. RC motors spin at a much higher RPM that you can use directly so a reduction is required. I am not sure if 14:1 is enough, but depending on the voltage you are planning on running you might be able to find one with a low enough kV rating.
I found a youtube video I saw ages ago of someone trying to Convert a Aprilia RS50 over to EV. They replaced the crankshaft with a RC motor and used the bikes internal transmission.
https://www.youtube.com/watch?v=5sPNl6ZWYms (https://www.youtube.com/watch?v=5sPNl6ZWYms)
Don't think he ever finished it but there is a forum post here
https://endless-sphere.com/forums/viewtopic.php?f=12&t=83316&sid=59a72f3e1f355f56490f0298e808cf00&start=25 (https://endless-sphere.com/forums/viewtopic.php?f=12&t=83316&sid=59a72f3e1f355f56490f0298e808cf00&start=25)
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Speaking of Aprilia RS50 conversions: Here are two photos of my old 2003 ICE bike which (after the engine exploded) was bought by a fellow in the San Francisco East Bay, converted to electric power using discarded Zero components (or so I heard) and then ridden at an EV event at Laguna Seca.
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Hi Demoni,
You're absolutely right - hub motor and swingarm !
I think the hub motor would provide the most elegant solution provided I could manufacture a swing arm. I'm 'scared' of that and also how to replace the existing internal drum brake with an external (disc, I guess) brake and the switch (or not) from cabled actuator to hydraulic. I think if I were to be doing this as a conversion for a 10, 20 or 30+ of this particular scoot then a replacement swingarm, hub motor and hydraulic brake would undoubtedly be the better option.
To be frank, when I dreamed up the idea I hadn't taken the internal rear-wheel gearbox into consideration and that's come back to bite me... Live and learn, I guess but...
With regards to the RC motor (Aprilia RS50), I'd considered this approach (I think I'd stumbled upon the same or similar vid) but ruled it out (probably too early and without enough consideration :-[ ) mainly due to :
1: I couldn't find a powerful enough motor 3Kw (+ at the time)
2: the motors I *did* find, that could maybe be considered, were all far to large for the available space, without a non-DIY amount of machine shop work
3: my final concern was how to 'adapt' the crank shaft to the motor shaft...
I gave up the idea as being too complex for your average DIYer on a one-off project (maybe I was wrong :-[)
The solution I have come up with is undoubtedly a compromise but I'll post some pics etc of the motor and 3D printed (test) bracket I've come up with. If it looks like the idea will fly then I'll knock up a bracket in 5mm aluminium and see how that goes...
More work and pics coming up...
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Time for an update ! I've made some progress with the motor :
The motor controller arrived !! Yaaay !!!
Initially, I removed the cylinder head. Once that was done, the swingarm was next. I found it easier to leave the swingarm attached to the scoot for the major kit removal as it helped support and hold the crankcase etc during the work. So, after the cylinder head, it was the turn of the oil pump, the starter motor and the ignition system.
I'll need to design some covers / blanks for the holes. I intend to route the motor cables through the square, oil pump hole so will make a blank specifically for that purpose.
Once the cylinder head, oil pump, starter motor and ignition system were removed I began to 'play' with possible motor positions; the crankshaft was 'annoying' me though - it seemed to always be in the way and I knew it'd have to come out for re-working or... something...
I tried all sorts of ways to remove the crankshaft... and couldn't... In the end, I used a trolley jack - I tried but couldn't move it any other way. The trolley jack did the job in a couple of minutes - live and learn, I guess !
The swingarm was placed, upside-down, on the trolley jack and 'tied' down with tie-straps all the way around the outside of the jack. The crank shaft was located centre of the trolley jack 'saddle'. The jack was slowly and pressurised, the 'saddle' extended BUT the swingarm itself was restrained by the tie-straps. Slowly, very slowly, being careful so as not to distort the swingarm itself, the crank shaft popped out - as per the centre image above. The whole lot was then cleaned up.
There simply wasn't enough space to mount the motor within the engine casing - even if I had the mind to attempt it ! Looking at the various 3Kw motors available I don't think I can get one much smaller regardless of the amount I'd be willing to pay and even then, the mechanical / machine shop re-work would be extensive (and, therefore, expensive !). In the end I began to see that the motor could be mounted in lieu of the cylinder head if I designed a suitable bracket. Out came Sketchup and then the 3D printer and in an afternoon I had an ABS bracket knocked up (in pieces - much as I would eventually need in aluminium) and welded them together with an acetone/ABS slurry. Effective !
Once I'd determined that the the bracket was correct for the motor, I went about mounting it to the 4 threaded holes vacated by the cylinder head studs - all the time being very careful not to break my template ! And, once I'd done that and noted the correct positions of the 4 x slots in the back panel for the new cylinder head machine screws. I say 'slots' - these are 4 x horizontal 20mm x 5mm slots allowing the bracket to be mounted to the crank case in a way that there would be 20mm +/- of lateral movement to enable future alignment of the motor pinion with the rear, gearbox, sprocket.
I then cut out and welded the same pieces all over again BUT, this time, in some 'scrap' 5mm aluminium I re-tasked from the skip at the local scrapyard.
Now I had something like the images below. I actually began to feel pretty pleased with myself... starting to believe the whole crazy idea might just work !!
The three holes in the bottom strengthener / spacer are to enable any water to drain more easily.
The motor is held rigid by the two pivot bolts at the bottom bracket and then the short arm at the rear of the motor (left hand side in the images) to help prevent twisting. The long arm on the top of the bracket, at the pinion / drive side of the motor allows the whole motor to rotate forwards / backwards (in relation to the scoot) and thereby enable the chain to be tensioned - much like an alternator adjuster-arm.
To be fair, after a wee bit of filing some rough edges, the whole system mounted up in 15 minutes
My job with the motor was almost done. All I had to do now was blank off the old / no longer used crankcase holes for the starter motor, crank shaft and oil pump etc being careful to route the motor cables through the now empty, crankcase and up towards the back of the scoot where I planned the electrics & controller would go !
Next is the Gearing, tidying up the electrics and batteries...
I was limited to 4 images... but... I have documented things on my (new) blog at www.ianwatts.online. You're welcome to see more stuff there...
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An update re: my (rather hopeful?) gearing...
I'm not sure this will work (given the gearing) but I have to start someplace !
I figure that it will be easier if I can the existing rear variator / clutch assembly (in some modified manner) to pass the drive through the gearbox to the rear wheel. I'm hoping the clutch / gearbox will be beneficial / not pose any significant problems... although some math with the ratios indicates a top speed of 11kph !! Hmm... To be frank, I think I'm going to need to re-visit this one BUT, at the current time using the existing variator / clutch assembly is the easiest way to get drive into the gearbox... I certainly can't see any way at all (bar a hub motor) of 'ignoring' or bypassing the gearbox - although I have looked at switching gear ratios within it (costly and of (at first glance) limited benefit !
So, to make a start and fit the new sprocket to the rear clutch ass'y, I stripped down the whole assembly and through-welded the sprocket to the two clutch plates (they will not be needed as the rear section of the variator anymore so...
I started by removing the nut from the splined gearbox input shaft. The clutch bell housing (right hand side in the image above) may then be removed, followed by the variator itself.
A large nut will be visible once the bell housing is removed. If you're planning on doing this yourself, then be VERY careful stripping the variator - it's under pressure from an internal spring (image below). I held the variator plates shut (their natural position under spring tension) and removed the large nut. In doing so the spring tries to release - keep that pressure applied, remove the nut fully and all comes apart as per the next image.
I then stripped the variator guide plates from the shaft and welded the 69tooth sprocket to both plates. To ensure the new sprocket remained central / true I made up a plastic spacer (again, using Sketchup and the 3D printer).
Reassembly was the opposite of disassembly (above) - apply pressure to the spring and start the nut off on its thread. Lock up the nut and refit the whole assembly to the gearbox input shaft.
If I find (as I'm pretty sure I will) that the clutch assembly is just too inefficient / isn't needed then I can always lock the clutch. I can also lengthen the gearing somewhat...
But... that's for another day !
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After my recent gearing work came the original / as-fitted electrics and their sorting out and tidying up.
Once again, like the strip down, this was pretty straight forward. Unfortunately, the Chinese used a strip, twist, solder and tape method of making joints within the wiring loom. They also had multiple earth / ground connections (using the strip, twist, solder and tape method) which in turn connected at both ends of a common (green) wire to the chassis. None too neat or pleasant to work with and definitely not simple to fault find. The cause of the intermittent spark did become apparent though - just a little too late for this ol' scoot !!
All the 'strip, twist, solder and tape' -type joints were removed and each item was individually tidied up. In all cases (there's not a lot of current involved here and it's all 12V) the earth cables were directed back aft to a common earth bolt.
Once the cable loom had been opened up it became possible to begin removing cables; the battery cables first, then the ignition and charge system (c/w CDI and regulator)...
At the end of an hour all that was left was lighting, ignition, side-stand down, fuel gauge, starter, kill switch and low oil cables.
The kill switch was modified (with an additional cable) from connecting the low-tension side of the spark ignition system to earth (thereby killing the spark) to being a pass through switch intended as an interlock for the controller/motor HV relays.
The fuel gauge cable was isolated as was the low oil level cable. These will be re-tasked later.
The idea is (once the scoot is 'up and running') to re-task the :
[1] low oil (red) warning lamp to be a low Voltage lamp (something like, 72V battery pack below 65V)
[2] the fuel gauge cable (full scale deflection at 0V / connected to ground/earth) to indicate battery pack voltage and, therefore, a kind of battery level indicator. An AVR Tiny will be used to pulse the gauge at a preset rate depending upon the battery voltage it detects (thereby adjusting gauge needle deflection)... Crude... but I don't like unused controls / gauges and it would be a helpful indicator whilst employing the existing panel gauge. An improvement may be to switch out the programming of the AVR to be a coulomb counter and, therefore, make it MUCH for useful... we'll see... that's a later-date project !
I have a made a small 12V Li-Ion pack (Panasonic 18650 cells again) (which will be charged by the DCDC convertor) and used to 'power' the ignition switch, via the modified 'kill' switch, and thereby energise the Controller <Enable> line and two (one HV/72V and one LV/12V) relays / contactors or, in my case SSRs (solid state relays).
All lights have been switched out for low-power LEDS, including the head light (VASTLY improved over the original headlight). The only challenge here was the standard method of earthing the indicators was 'novel' in that the Chinese manufacturer used the instrument panel indicator 'On' tell-tale as a ground for the active ones. Due to the extremely low power required by LEDs, this simply meant that ALL indicators flash when either direction is selected. The way I chose to work around this was to trace the two, left/right, indicator cables at the panel tell-tale and insert standard 1N4001 diodes into each. This way one indicator direction cannot back-feed the other. Hey-presto - all LEDs including panel lights.
Finally the new 'loom' was routed through some braided sleeving with cables exiting at their required points along the route.
Now onto the main EV electrics !!!
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You're making a lot of progress quickly.
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Thanks for the encouragement, Bill. To be frank, it's all going pretty smoothly - almost too smoothly ! I'm working with baited breath...
I thought that before I start the main / primary EV electrics I should 'tidy up' a little bit first.
To be fair, at this precise time, given that I have serious doubts as to the effectiveness (and, therefore, finality) of the scoots gearing, I have decided to carry out the most basic of tunnel / cover modifications. All I did was to mark out the upper and lower limits of the chain drive between the motor sprocket and the, recently refitted, rear gearbox input sprocket
and then cut the marked area out with a hacksaw and file. A little sandpaper on the edges to finish and...
Once the marker pen is cleared off with some white-spirit then all will be well for a proper, chain-on test...
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These are to protect the internals form dirt, grit and water ingress as far as practically possible. In the case of my scoot, I have various cover / blank plates to design and fit :
[1] Oil pump blanks (I need to design one with a cable (motor) pass-through slot)
[2] Starter motor blank
[3] Crank shaft blanks
I reverted back to SketchUp again and then the 3D printer and came up with the various designs which I then printed in yellow ABS (just had a lot of yellow lying around :D ) and then fitted.
It took two iterations of the square oil pump blank to take the motor cable... but all-in-all, no major issues.
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With most of the 'boring' stuff out of the way I started off trying to work out where to site the batteries I would be making. Once the site was chosen I'd have a better idea as to final available / required dimensions. I had already played about with weights etc and pre-set any pre-requirements I had :
[1] they must be removable for security, off-scoot charging and protection against extreme temperatures.
[2] being removable they need to be pretty light - around older laptop weights; 1Kg (plus or minus) would be great. For me 'lighter' not only means more easily carried about but less likely to be thumped around when placing them down etc and more manoeuvrable getting them on-off / in-out of the scoot.
[3] two (or more) smaller packs would tend to suit the previous requirements whilst benefitting from more spaces on board the scoot (there seems to me to be a lot of 'small' spaces available but few large ones) and also lends them more readily to be re-tasked between projects.
[4] maintain as-low-as-possible a centre of gravity; a top heavy scoot is horrible to handle both in traffic and whilst re-positioning/parking it by hand
[5] if at all possible, maintain the helmet area below the seat. Having said that, on this scoot any helmet would have to be a pretty small open face or half helmet if it were to fit at all !
Anyways, I had already selected 72V : 13-14AHr per pack equating to a 20S4P (1Kw) minimum pack power / size. Each pack was to be thermally protected and be able to be individually and / or group charged.
From the outset, I had hoped to build two 'long and slim' (20 cells long, 4 cells wide) packs and site them under the riders' feet, within the fairing area. Unfortunately, without massive frame mods, there simply wasn't enough space for this to be feasible.
Next I looked at using the space vacated by the recently removed fuel tank (although, in reality, too high - from a centre of gravity point of view.). The main (and pretty much insurmountable) problem here though, was that the seat lock bracket was in the way; the two packs would fit (side-by-side) but they'd not be removable. That coupled with the height 'issue' meant option 2 was, again without major grinding and welding work, a dead end too !!
Then I looked at designing and building two exhaust-style 'cans' - one for each of the battery packs and either side of the scoot... a wee bit drastic but definitely worth investigating. Maybe at a later date.
In the end I decided to fit them directly above the motor; in the area below the seat, at the very bottom of the seat 'box'. It would mean removing much of the base of the seat-box - so that they could be taken out (for in-house / external charging) and put back in again - but this was the most feasible of the options I'd looked at...
Once I had the location sorted it came time to make a bracket/shelf arrangement for the two battery packs to sit in above the motor. Initially, I made a mockup in cardboard then in some left-over 10mm EPA foam that was lying around. Once that seemed to be OK, I re-made the bracket so that the original would fit inside it, removed the original and fibreglassed up a shelf unit complete with side and fixing points to locate it securely on the scoot framework whilst, at the same time ensuring sufficient room for the motor to be rotated for chain tensioning... A bit for sanding and painting and...
With the battery mock-ups now fitting snugly in their new 'home' on board the scoot I gingerly cut, re-cut and cut again (and again - little by little) the base of the under-seat helmet / storage box to allow their insertion and removal. That all done, it was time to move on to making the battery packs. After gathering together the parts; NCR18650GA batteries, SplitPort BMS, Thermal CB, Charge Plug/Socket & Anderson connector, etc... I began, with the help of the Spot Welder I built for these 18650 cells, SketchUp and my 3D Printer to build the battery packs.
I ended up :
...Building the packs - 20S4P configuration...
I decided to spot-weld (not solder) and fuse the cells (top and bottom / anode and cathode). I also decided to go with a split-port BMS and a thermal, 50A circuit breaker for output protection. I designed in 2 x thermistors and placed them 1/3 of the way / 6 cells rows in from each end-cap. The cables were routed to the CB end-cap and left insulated for a future date add-on project. The idea being to enable battery cooling / heating during charging and battery cooling when running and too hot. I haven't gotten round to this just yet but, when I need a break, I am programming and testing the AVR code.)
...Printing out, building and connecting up the end caps...
(I designed the end caps with three ridges - for the heat shrink to grip onto)
...and putting them all together before applying 3mm foam protective sheet and heatshrinking the lot...
NCR18650GA cells are 'C' rated at 3340mAHr. 'C' effectively equates to capacity (measured in AmpHours).
In the packs (designed & built above) there are 4 x NCR18650GA cells in parallel. That produces a total of (just over) 13AHr. They are rated at 3C continuous (10C max) discharge and 0.7C designed charge current which equates to a 9A charge current PER battery pack, therefore, a 10AHr charger would be fine (seeing as a 9Ahr charger isn't readily available and 1 additional AHr shouldn't cause an issue) for these packs.
Furthermore, whilst each pack has a 'C' rating of (just over) 9AHr, the PAIR of packs onboard the scoot will have a 'C' rating of (just over) 18AHr, so a 20A charger COULD be used IF the battery packs were to be charged as a pair (with a similar caution as per the 10AHr charger for a single pack).
I purchased (quite a while ago) a 72v 5AHr charger, however, should I wish to install an onboard (on the scoot) charger than to minimise charge time a 20AHr unit would quadruple the available charge current and (a little simplistically) speed up the re-charge time accordingly - if the room is available at the end of the project.
Either way, I don't foresee an immediate need to have 'high speed' charging and intend (at this point in time) to use the 5AHr charger for both onboard (dual / paired pack)and in-house (single pack) charging. As as 'aside' the 5A charger I purchased was $60 (USD) whereas a 20A version would be around $160 (USD) - not a huge increase for a far quicker re-charge - if required. The real 'downside' is :
the 5A charger comes in at around 1Kg and has dimensions around 200mm x 110mm x 60mm
whereas
the 20A version comes in at around 3+Kg and a ballpark size of 330mm x 175mm x 115mm.
Finding enough room for the 20A charger onboard the scoot would be much more difficult - in my case ! At some point I'll do a more in-depth study and comparison of 5A, 10A, 15A and 20A chargers... but not today... I'm still on a mission to finish this scoot !
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I'm only allowed 4 images per post so I have included the last image of a made-up battery pack here !
I make most of my updates there first and then copy'n'paste whan I can to the forum. I hope that's all allowed / OK. There are a lot more images etc on the website : www.ianwatts.online.
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Again, I'm impressed by your pace with this project. Good info on your blog. I've only just started toying with the idea of my own EV conversion but I'm no stranger to designing and building new machines for the commercial market. Your project gives me encouragement.
I especially liked the idea of simulated exhaust cans for battery housings. On a larger bike that could work very well... and provide appropriate venting should I "let the smoke out."
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Hi Bill822,
Thanks ! To be totally fair, I'm probably a couple of days more advanced in reality than I am updating the forum... Having said that I have also had 6 months or so to plan this... so I do feel a little bit of a fraud in that when I started the project some 5 to 6 weeks ago I already had a load of research notes, sketches and even some basic SketchUp designs in hand... BUT... I'm still very grateful for the support... I think 6 weeks in my son's world is a lifetime - he's almost stopped enquiring as to "Are we nearly there yet, Dad ?" :)
I'm really hoping to have a 'dry' test by the end of the weekend... things are moving much faster now I have the basics pretty much finished.
As to the 'cans' for the batteries. I really like the idea but my printer doesn't go large enough, easily enough (without making a design in multiple
clip / glue -together pieces) although I have seen that I can buy empty cycle battery pack 'enclosures' on eBay for 15-odd quid / 25-odd USD and with some modifications,... who knows ?... they might just look cool... it's on my list of 'possible future jobs/projects'...
Anyways, thanks again.
Good luck with your Zero.
I'm off to start the controller electrics. Hopefully, no smoke !! ;D
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This week I've been busy with the last major part of the conversion: siting the controller and associated components.
The original ICE kit has been removed.
The original wiring has been serviced / repaired / updated to remove no-longer required cabling and modified to re-task cabling to suit the new electrics and add any new / additional cabling for the imminent electric conversion.
The 3Kw BLDC electric motor has been fitted on a custom, adjustable, aluminium bracket and the cabling routed aft and up to the intended controller position.
The belt driven vari-drive has been modified for a chain drive with rear sprocket and the clutch has been left insitu (to start off with but I have my doubts here...).
All lighting has been switched to LED.
The battery pack tray has been built and installed.
The 2 x 72V, 1KW battery backs have been built, charged and tested.
The fuel filler cap has been replaced with a 3D printed charge point complete with waterproof cap (still need to update here with pics etc).
The next step was to design and build the controller 'tray' and then mount the controller before adding a 2nd tier shelf arrangement on which to mount the other electrical / electronic components (fuses, relays, DCDC convertor, 12V battery etc) and connecting the systems up prior to testing. Now it's becoming exciting...
Controller tray
Now that the batteries were sited directly above the motor, there was enough space (with a little modification) to site the controller (and ancillary parts) in lieu of the petrol tank / aft of the rider's seat. This are is a quite 'unforgiving' space in that the rear wheel is directly below (don't go too deep) and the fairings are immediately above (don't come too high). To boot, access to the rear / brake light is from this area too (don't go too far aft) and the front end is limited by the seat-lock bracket (don't come too fare forward)... BUT... all-in-all this is controller space !! Dry and well cooled...
Having decided all would be well, I set to designing and fabricating the tray. This was no job for SketchUp or the 3D printer - just cardboard, scissors and tape before moving on to foam and then fabrication with fibreglass...
It quickly became apparent that no matter how much I dislike cutting holes where not absolutely necessary and no matter how much I 'squeezed' or moved the controller or how I oriented it (within the constraints that I had) I HAD to cut two holes in the seat support bracket to enable the cables to pass through and, thereby, allow the controller to move far enough forward to facilitate access to the tail lights. In this case though I couldn't see how the holes would weaken the overall structure so... I cut the holes, rust proofed them, glossed over and trial fitted the controller...
All looked good so the next step was to mount the controller and the two SSRs with their heatsinks. I guess the 'norm' here is to use HV contactors / relays but Solid State Relays use so little power when 'On' and have the advantage of being so very flexible with their energising voltage that I thought I'd give them a go. They have worked great in other projects (like my Spot Welder) so they deserved a chance here too... especially as, having no moving parts, there can be no contact bounce / accidental disconnect due to the higher vibration of the scooter... Anyways, I gave them a go !
Two of them, one for the low voltage (12V) / controller energising and one for the high voltage, (72V) motor.
The recently removed fuel tank had been through-bolted at four points - top and bottom left and right of the recently-fitted controller tray. These were to be re-tasked to locate the "ancillary components shelf" which (because it allows me to see the controller & SSRs below and because (I think) it looks super cool - not that, when all the fairings are back in place, it will be visible !) was to be made form 8mm clear Acrylic sheet...
After test fitting the controller tray and acrylic 'shelf' it was time to drill 2 additional (corner) holes in the tray for drainage (there's just bound to be some water ingress) and finally fix it to the scoot frame.
I ended up with the painted black, GRP tray housing the controller, the 2 x SSRs and their heat sinks. The tray is angled down toward the front of the scoot (towards the bottom of the image); this is where the 2 x 10mm drain holes are situated.
The SSRs screw to their (black) heat sinks and the heatsinks are through-screwed into the base of the controller tray. The two holes previously drilled in the seat-lock bracket enable the controller HV input (thick red and black) and motor phase cables (thick blue, yellow and green) - both right hand lower corner, together with the control cables (thinner, multi-coloured) - left hand lower corner, to exit the controller tray without chafing etc...
Now, things began to move really quickly !
This was the part I'd been really looking forward to !!
The first job was to finish siting the SSRs and connect the 2 x battery hook-up cables (terminated with Anderson connectors) The DCDC convertor was fitted next, followed by the Li-Ion 12V battery, the shunt (I think I'm going to want to know charge / discharge current and voltage etc) and then fuse holders. I added a pair of (red / black) banana connector sockets to measure the battery / DCDC convertor voltage and to connect an external 12V source / charger in case of 'flat battery'.
Two SSRs :
... both energised by the Li-Ion battery via its fuse, the ignition switch and the kill switch.
One 10A SSR (left hand side) for the low voltage (12V). This unit feeds 72V to the DCDC convertor.
One 60A SSR (right hand side) for the high voltage (72V, motor / controller). This unit feeds battery pack 72V to the LV / 10A SSR (which feeds the DCDC convertor) and the controller.
One DCDC Convertor :
Connections to the HV SSR output, shunt ground and the 12V fused rail.
One diode :
In-line between the fused 12V rail and the Li-Ion battery The purpose of the diode is to enable Li-Ion battery pack charging whilst preventing back-flow from the battery to any on-board items - except the DCDC convertor (for charging)
Three fuses :
DCDC convertor (all onboard 12V)
Ignition / controller enable (basically, kill switch OFF and Ignition switch ON puts 12V onto the 'power lock' / controller enable.
Onboard lighting / horn electrics
One shunt :
One side of the shunt was connected to both battery -ves, whilst the other side was connected to motor controller -ve, DCDC convertor -ve and chassis ground.
Final steps : the motor cables (green, blue & yellow) were connected via a 50A terminal block to the controller. The controller / motor hall sensor connections were made (plug'n'play)...
... and then onto the throttle, brake, reverse and power lock cables... but those are for tomorrow... (mostly because it's late and I note that the throttle cable is terminated with a different plug-type to the controller socket !
To be frank, I also have :
the High / Low speed connector to make (naturally I only need the HIGH !) but (if only for testing) i'd better make a PAIR of connectors - one for Hi and another for Lo speed - or I could add a Hi/Lo switch...
the 'fuel filler' / charge port to connect. I have designed it (SketchUp) printed it (3D Printer), fitted the matching 72V charge connector into it and test fitted it on the scoot but I need to add the diode protection, connect up and fit it...
dry test the lot...
reassemble the scoot and let my son test it for me... receive his 'review' / critique and...
and... probably, a load of other small jobs I haven't remembered to write down here...
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Again, the fourth, last, most interesting (in my mind) image wasn't accepted - I'd hit my 600kb limit. Here's the one I wasn't allowed to post :
as with all previous posts I've more info on my web blog: https://www.ianwatts.online/blog
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This was some fun ! I took some measurements and started designing (SketchUp, again) a replacement fuel filler neck & cap some weeks ago.
First I thought I'd use the same Anderson connector as was on the batteries I intended to build (and have since completed). I can't, right now, remember why but I changed my mind and used the XLR 4-pin socket to match the plug that arrived with the charger... the same sockets in fact as I fitted to the two batteries for charging - keeps the parts list simple :D
During first fit though, I decided to change the design (again) to a 3pin IEC mains 110/220V AC socket - as per the mains cable between the wall outlet and the charger input. This was mostly because, having a drink at the bar, discussing charging one night, we all agreed that the charger would always be required to charge the scoot (obviously). My idea was that the charger should be carried in a back-pack / ruck-sack or, if space wasn't too important, under the seat ! It was pointed out to me that the charger would then need to be connected to both an available wall outlet and the charge socket, behind the seat. Seemed pretty obvious to me... what wasn't so obvious was that everyone agreed it would be simpler just to connect the bike to the wall socket - no charger to play about with or fall off the seat (or wherever else it had been balanced) and break. Seems reasonable ! In addition the space under the seat (on this scoot) is pretty poor anyways (I think I've already mentioned that somewhere along the line...) so... why not use it for the charger ? ? ? As a bonus, the charger is always dry under the seat - it wouldn't necessarily be so, balanced on the seat / next to the scoot during charing...So... why not indeed ? !
And, as it transpires, there's still some space left over for documents, tools and gloves etc...
The 'downside' to this approach is that the scoot will have a fixed / permanent mains AC item wired in at all times and although it won't (obviously) be live at all times, I'm unsure as to any safety regulations with this approach. Having said that, the IEC connector could always be swapped out for the XLR connector in around 10 minutes... so... What's not to like with this approach ?
The final connector, fitted on the scoot with the fairings back in place, looked pretty cool / not totally out of place... almost as if it was part of the original Chinese scoot...
The design incorporates an 'O' ring on the lid / cap and a large overhang to reduce the chances of water ingress. It has two large drain slots built in (semi-circular, forward and aft of the raised, central, IEC socket, to prevent water build-up if any gets in.
The mains cables (L, N & Earth) are soldered and heatshrunk before being liquid silicone sealed. The cable terminates in the under-seat area with the original IEC plug for the charger. The charger output (XLR connector) connects to the, now redundant, original XLR socket thereby keeping it all fully removable for service etc...
A little smear of silicon grease on the 'O' ring and the lid / cap is a simple friction twist fit !
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Zero uses the IEC socket for charging so it should be OK as far as regulations. Not so sure about the IEC into the charger under the seat. Make sure there is an earth connection through the IEC/charger housing to the chassis.
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Hi Bill,
Thanks for that - No, I haven't !
I hadn't given an earth point too much thought and stopped thinking about it completely when I tried to work out where to connect the cable on the charger ! :-[ (and the scoot) !
I will though !
It'll go onto my list of things to finish. Before I do though... is there an earth wire from the charger itself on the Zero or could I simply 'tap into' the earth cable where I soldered it at the socket ? Pedantic possibly... but I only ask because
[1] there is no dedicated earth point/stud/screw on the charger (I could quite easily add one though) and
[2] whilst the charger is now 'on board' I haven't screwed it down / fitted it permanently as it's above the batteries (and they're removable) in the seat box and I only have the one, so wanted it to remain removable... (not that I plan on removing the batteries much !
[3] I guess there's no 'issue' with having HV (72V) -ve, LV (12V) -ve and mains 240V ground all connected ? That IS how it would have been done on warships, yachts and commercial ferries etc but... apart from anything else that was quite a while ago now... and either the rules may have been updated or my brain is more befuddled that it used to be...
...probably a stupid question.
The charger should though, I guess, be screwed down with a visible earth cable linking it to chassis ?...
Just hadn't planned it that way...
It's quite amazing really... at first glance, there appears to be loads of space on these scoots but when it comes down to it, there's really very little... :o
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First, I am not familiar with UK/European regulations which I have heard can be very specific. I am also not an electrician by trade.
I would expect the earth (we say ground) pin on the IEC connector in the charger to be connected to the metal housing of the charger. You can verify this with a multimeter. If so, a wire attached to the housing and the frame would provide a current path in a fault. This is what I would do myself but may well not meet code. On industrial (mining) machines I built for worldwide use I always connected an earthing cable directly from the power connection point to the frame of the machine and never heard of a problem with compliance.
Yes, it should be fine to share an earth between AC and DC components. You have a connection to earth through the kickstand anyway, though unreliable. I did it all the time back before I sold my company. Where you can have issues is if you have two separate plug-in power supplies both providing DC. Even then problems are rare.
With Chinese designed Ebay sourced components, of course, all bets are off. It sounds as if you used quality parts though.
EDIT: I should add- the most likely cause of a ground fault on your scoot would be chafing through the insulation of the mains cable since it will be subject to considerable vibration in use. Exposure to moisture should also be controlled.
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Thanks,
I think we're both on the same page here...
I always connected an earthing cable directly from the power connection point to the frame of the machine and never heard of a problem with compliance.
That's my current plan too. It does mean removing the fairings again but... I could do with a few other tweaks in there while I'm at it so I'll get onto that later this week (I'm away 'til Friday but...)
On another note, I did manage to do a dry-test / get the rear wheel spinning last night so WooHoo !!
Everything looks pretty good at the moment but I did notice some 'stutter' at high(e)r revs... Having no 'load' (wheel off the ground) I'm unsure if this is a phase / hall sensor or some kind of rev-limiter issue. I'd also say that the clutch (original as-fitted kit on the input shaft to the rear-wheel gearbox) needs to come off... I'll do a load more tests later in the week but you really do need the motor to spin up before the clutch engages and moves the rear wheel. Maybe that's a good thing but...
Anyways, like I say, I'm away til Friday so will content myself (with frustration) to giving these 'issues' some thought and wait til I return. Probably, first check would be with a tacho-gun on the motor gear / rear wheel to see what the actual revs are... Apparently this motor spins up to 5000rpm (with 5900 as maximum).
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I was thinking about the clutch and gear ratios. I was surprised you left the clutch in place but it might allow you to run a higher gear (lower ratio) to reach higher top speed while still having enough torque to move away from a stop without overloading the motor. Just a guess on my part.
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You're right... leaving it in was pretty much always going to need a re-visit... but... I have a plan - nothing new, I decided to leave as-was at the time BUT noted that a quick, 2 minute, weld job would have some short studs welded to the clutch housing that would lock into the driven part of the assembly thereby bypassing the clutch completely (whilst, for tests / until I know what's required for sure, leaving the hardware in-situ) . Not only will it be only a few minutes to do but it's totally reversible if I change my mind (again?!) ;)
My second 'concern' at the time was selecting a small enough rear sprocket. The gearbox input, being of a tube-around-a-driven-shaft arrangement has a 38mm diameter making a sprocket selection rather limited. I'm pretty sure that the 5000rpm (motor) to sprocket (13tooth) to rear sprocket (69 tooth) to 1.5m circumference wheel will deliver very slow speeds but not knowing the motor and scooter gearbox etc thought I'd give it a whirl... I pretty sure I'm going to need to redesign the whole 'clutch' / 'vari-drive' / input shaft arrangement to get a more workable solution... I won't know that for sure though until I tacho things... so, we're still on track... I think ???
More worrying for me at the moment is the this motor/controller 'stutter' I mentioned (only at high(er) revs) but again, the tacho will point me in the right direction. It may simply be that the motor is maxing out its revs and somehow limiting itself - much like my KTM does once it hits max ! Well, that's what I'm hoping for anyways - I don't want to have to deal with a motor / controller issue at this stage.
I'll keep pondering and revert once I'm back at the scoot.
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In my recent post about my motor stutter, I forgot to update with the work around the final connections to / from the motor and controller...
On the home straight now !
Just a bunch of wires (all with plugs / sockets on) to connect to the scoot and we're pretty much ready for a dry test !
[1] Throttle / Twistgrip
It was day 2 or 3, I think, when I got round to disconnecting the twist grip cable from both the carburettor and throttle ends. After that the original handlebar grips were pretty simple to remove; friction fit, so... a little brute force... and off they both popped. The throttle / 5K twist grip and clutch side had already arrived...(again, a friction fit) and were pushed on taking care to align the right hand / throttle cable exit so as not to interfere with the front brake or cylinder...
Unfortunately the connector wasn't the same type as that on the controller harness. Fortunately, I had some spares, so removed the un-required, black, cable end connector, trimmed the three cores, matched up the colours (red/+ve, black/-ve and green/throttle), crimped on new terminals to match the new connector and connected the cables / plug'n'socket !
Throttle... done... until the dry run / test !!
[2] High Level Brake
According to the manual, this is to remove power from the motor when the brake is applied - makes sense. But, upon reflection... that would mean that pulling away on a hill would require a little more... finesse / timing... As this was simply a question of adding a suitable connector to the brake tell-tale I'd already 'T'ed off the brake light cable (during week 2 electrics tidy-up) and putting cable plug into controller loom (beige wire) socket I thought I'd add an in-line switch to enable / disable this feature. I mounted the switch adjacent to the fuse panel.
In theory, 'making' the switch would disable motor power whilst one or other (or both) of the brakes were on and 'breaking' the switch would disable this feature, thereby enabling power to the motor even though the brakes were on ! It took me no more that 15 minutes to complete so I thought it was worth it ! We'll see...
[3] Hi-Speed / Lo-Speed
The controller loom has a 3-wire (blue/black/white) connector. Apparently blue/black = Hi-Speed and white/black = Lo-Speed. Making a change here (switching between Hi and Lo speeds using the cable loom), when all the bodywork was back in place, would be difficult, I thought. So, again, I added a wee switch, adjacent to the High level brake switch at the fuse panel to select Hi...or... Lo.
A little more time to complete than the brake switch but... bound to be useful... although I'm sure the only 'real' / 'likely' position will be High !! Again, we'll see...
[4] Cruise control
The controller comes with a black-white cable pair for cruise control... I thought there would probably be more disadvantages to this that advantages... and I'd already allocated the kill switch as Controller 'Enable' so... there were no more handlebar switches and... adding one wouldn't be too easy / pretty and... like I say, why would 'Cruise' functionality be required on a wee scoot ? !
I left this connector in the loom - disconnected.
[5] Reverse
The controller also has a black/blue cable pair for reverse... I'd already modified the Starter button for just this purpose so... I crimped the terminals onto the two wires I'd led aft to the controller area from the Starter switch and connected the two up. In theory... we've now gotten a Reverse !!
[6] Display
This is a single purple cable exiting the controller. I have absolutely no idea as to what capabilities it has or what specific display to connect it to. Currently I have left the original Chinese instrument panel display as-was EXCEPT where I'd taken the fuel gauge cable back to the controller / shunt area along with the Low Oil Warning lamp cable. These two are going to be re-tasked as battery level / SoC gauge and a Lo Voltage (<68V ?) lamp...
[7] Hall sensor
The 6 pin hall sensor cable existing the controller simply plugged into the matching cable exiting the motor. Simple.
[8] Power
The thick red and black cables exiting the controller were connected :
red --> HV SSR out (HV 'relay' output terminal)
black -> output side of the shunt (opposite side of the shunt to the battery -ve terminal)
[9] Motor phase
The thick blue, green and yellow cables existing the controller were connected to the same cables exiting the motor via a 50A terminal block.
[10] Power Lock
The controller has a power lock cable. The controller will not become active / energise the motor if this cable is not connected to 12V. This cable was, therefore connected with the 2x SSR energising cables to the ignition switch via the kill switch and side-stand switch.
If the ignition switch is 'Off' or the kill switch is in the 'Off' position or the side stand is down then this cable is disconnected from 12V and the controller remains inoperative.
[11] Anti-theft
As of yet, I don't have an alarm for the scoot. I did spend a little time looking into bluetooth , and other keyless-type alarms but although pretty cheap I felt that, for where we live (extremely quiet) didn't really require anything... yet...
[12] Control panel electrics
During the electrics tidy-up phase I 'found' the cable (original ignition output) that supplies the instrument panel and, therefore, the onboard scoot electrics (head light, side lights, indicators and horn etc...) This cable was connected, via a 10A fuse, at the fuse panel to the DCDC convertor output. Remember the DCDC convertor is fed with 72V from the LV SSR only when the ignition switch is on and regardless of the kill switch / side stand positions.
All electrics finished (NOT tested). Just refit the battery tray and connect up the Batteries !
Now, I'm almost finished, I can smell it... I'm off to dry-test... YIPEE !!
Couldn't stop myself, ignition On and the lights all work... the horn doesn't.... hmmmmm
Anyways, the motor spins up, rear wheel moves... Brilliant... But...
As I added power I noted a motor 'stutter' and wasn't sure why... the last post was about this so I looked into it with a tacho gun... next post...
As previously, I have a load more pics but couldn't upload them here.
They are, however, if you're interested on my blog : www.ianwatts.online
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At the outset I decided it would be really handy to be able to see battery voltage and motor / controller current primarily for test purposes but also whilst riding. However, because I hadn't found a relatively in-expensive meter and because it was simpler at the time and because I really had no idea where I would fit such a meter on the bike and because I didn't want to 'invest' in 'just' a V/A meter without knowing if I would later wish for more (power, temperature and maybe speed...) and because... because... because...
all I did was fit a 100A shunt and a 5 pin test port (both of which I had) ;
pin 1 = Gnd
pin 2 = 12V (DCDC converter
pin 3 = 72V (Battery pack)
pin 4 = Shunt 'A'
pin 5 = Shunt 'B'
All in all a really simple 'test port'...
Later down the line, I found a volt / amp meter on eBay (about 10 euro) using the same 200mA shunt. Needless to say, I ordered one and here it is cabled up and plugged in to the test port :
Now though, some 6 weeks into the build, I've arrived at this point and I really think I'm going to need to see this stuff whilst riding. So, whilst I had the covers / fairings off (to add an earth cable to the charge IEC socket - good point Bill), I'm revisited my 'test port' idea and ran a multi-core, screened, cable from the port up to the instrument panel and terminated it with a standard cable socket. In fact, at the same time, I ran a second multi-core, screened, cable from the port up to the instrument panel although not having any immediate real use for it - I'm bound to want it later and, if not, nothing lost !!
Keeping to my original, circa 800Euro costs, I still couldn't find a waterproof V/A meter, that could be retro-fitted on the scoot and be seen whilst riding, for any reasonable price. There was, however, a clock built into the instrument panel... maybe I could remove it and re-task the vacated space for the new V/A meter...
Anyways, like I said, I already had all the covers off again, so I removed the instrument panel and stripped it; 3 screws and it was off, 4 more screws and it was opened up, 2 more screws and disconnect 3 cables and the clock was out. No damage done...
Unfortunately, no matter how I tried I couldn't fit the V/A meter in it's place - it was simply too tall. What I came up with though was to split the two 3-digit displays into two, and site them separately.
I left the voltmeter on the PCB - it fitted just fine in the available space - then added 100mm of cable between the, now removed, 3-digit display panel (Amps) and the original solder pads on the PCB. I then re-sited (with a little help from Sketchup and the 3D printer) the Amps 3-digit display within the housing...
I then fitted a matching cable plug to the previous one I'd fitted on the end on the new cable from the controller / battery area to the instrument panel, connected it up and tested it all out...
Result !
All's good... ready for testing !
So... back onto the motor 'stutter' and clutch...
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Some of the images I couldn't post above.
more on my blog at www.ianwatts.online
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After 'playing about' with the Volt / Amp meter it was time to re-visit the motor 'stutter' and the un-modified clutch.
I grabbed my hand-held tacho (nothing special here, 15-oddEuro on Amazon), removed the chain between front / rear sprockets and applied a little reflective tape the motor shaft / gear.
Ahhhh.... All became apparent... The 'stutter' kicked in at between 5700rpm and 5850rpm. The light dawned... with ears alone, I had absolutely no idea the motor was spinning that fast !! Oops ! The stated maximum motor revs is stated as being 5000rpm and 5900rpm absolute tops ! OK the controller was either deliberately limiting the revs of I'd reached the motor / controller capability limit... either way... " I have a problem Houston ! "
So, using the tacho it became apparent that the onboard clutch only kicked in at around 3000 motor rpm.
The motor arrived with a 13tooth sprocket and the lowest rear (driven) sprocket I could find with a large enough centre through-hole (to pass over the rear vari-drive / clutch drive shaft) was 69tooth. I should have done some more math... Idiot !
Anyways, couple the 13 / 69 sprocket ratio, the clutch and the, internal-to-rear-wheel, gearbox ratio of 14:1 and... nothing surprising here... high motor revs = low wheel revs ! I should have thought of this way before now. Idiot (again!).
OK. I immediately reverted to a plan I'd been concocting that was to simply lock off the clutch by welding 4 short studs between the outer (driven) clutch bell-housing and the inner (drive) clutch pad plate. That took 10 minutes; I popped then off the end of the gearbox input shaft, slipped the bell housing off, welded on 4 short 10mm studs and reassembled (the studs simply located in 4 similar holes in the driven (inner) section of the clutch.
Stand up, wheels back on the floor and... OK... 11kmh max speed but.. although I'm disappointed at the, not-so-dazzling, top speed, I'm also grinning - I <b>have</b> converted a petrol scoot to an, albeit rather slow, electric scoot !!
After a poodle (I wanted to say 'whiz' but that really wasn't the case) around the garden and patio with my wife saying... 'Nice dear... but won't won't the milk have gone off by the time you get it home ??? " I reverted to the garage. I stripped down the clutch assembly and started to re-work the plan... but this time with some math first !
Accepting that there is very little I can do with the internal-to-rear-wheel gearbox (14:1) ratio and that the maximum motor revs are 5000 (forget about the over-rev portion (that can simply be a later date 'Brucie' bonus ! ) and the rear wheel circumference of 1.45m I calculated for a 45Kmh top speed (matches the original top speed - although still not dazzling) :
5000rpm x chain/sprocket ratio (CSR) x internal gearbox ratio (GBR) x 1.45 = speed (mtrs / min)
=> 5000 x CSR x GBR x 1.45 x 60 = Speed (mtrs / hr)
convert revs per minute into revs per hour (because I need Km per hour - kmh - at the end)
=> (5000 / 1000) = 5
=> 5 x CSR x GBR x 1.45 x 60 = Speed (Kmh)
I know GBR = 14:1, so 1 / 14 = 0.0714 (GBR = a multiplication factor of 0.0714)
=> 5 x CSR x 0.0714 x 1.45 x 60 = Kmh
to isolate the CSR (chain sprocket ratio)
5 x 0.0714 x 1.45 x 60 x CSR = Kmh
=> 31.1 x CSR = Kmh
... or...
=> CSR = Kmh / 31.1
so, for a top speed of 45Kmh :
=> CSR = 45 / 31.1
CSR = 1.45
and, for a top speed of 60kmh - illegal :
=> CSR = 60 / 31.1
=> CSR = 1.93
and for 75kmh - also illegal but fun to work out ;) :
=> CSR = 75 / 31.1
=> CSR = 2.41
That's to say;
for 45kmh, the front sprocket has to have 1.45 more teeth than the rear sprocket
for 60kmh, the front sprocket has to have 1.93 more teeth than the rear sprocket
for 75kmh, the front sprocket has to have 2.41 more teeth than the rear sprocket
So, math over, the motor arrived with a T8F sprocket / shaft fitting, that's to say a double 'D' fitting on a 10mm shaft or a 10mm shaft with two flats cut into it, 180' opposed.
The challenge here is that for the (theoretical) power involved (3000W / 3Kw) this type of fitting doesn't allow for larger than 17tooth sprockets (not unless custom built - or someone has a source I haven't found ;) ) To be fair, above 17tooth is probably placing a HUGE amount of stress (even with the 14:1 rear gearbox ratio) on the motor shaft and as the number of teeth are increased so too does the sprocket diameter and, therefore, so too does the side or cross stress and the torsional stress.
The long and the short of all this ?
17 teeth front sprocket is (probably) the limit (but, if I could find a 19tooth sprocket I wouldn't mind a try !).
So, taking the 17tooth front sprocket and the CSR for the three 'required' top speeds above :
to calculate the drive ratio of these two sprockets :
Front Sprocket Teeth (FST) / Rear Sprocket Teeth (RST) = CSR
FST / RST = CSR
=> RST = FST / CSR
Front sprocket teeth (FST) = 17teeth
feeding the numbers into the final equation :
for 45Kmh and a CSR = 1.45 :
=> RST = FST / CSR
=> RST = 17 / 1.45
=> RST = 11.7
obviously, a sprocket can only have a WHOLE NUMBER of teeth. A 12tooth sprocket will provide a top speed of slightly under 45kmh, whereas an 11tooth sprocket would provide a slightly greater than 45kmh top speed.
for 60kmh, CSR = 1.93
=> RST = FST / CSR
=> RST = 17 / 1.93
=> RST = 8.8
A 9tooth sprocket will provide a top speed of slightly under 60kmh, whereas an 8tooth sprocket would provide a slightly greater than 60kmh top speed.
for 75kmh, CSR = 2.41
=> RST = FST / CSR
=> RST = 17 / 2.41
=> RST = 7.1
An 8tooth sprocket will provide a top speed of slightly under 75kmh, whereas an 7tooth sprocket would provide a slightly greater than 75kmh top speed.
NOTES
It should be noted here that a 9tooth sprocket is the smallest I was able to find BUT I'd be very surprised if the chain ran smoothly over it on a standard shaft. Obviously, sprocket tooth stress increases with a lower number of teeth on that sprocket - there are simply fewer teeth for the chain to engage with and transfer power to.
It should also be noted that whilst some even number sprockets exist within the available 9-17 tooth range, there are more odd numbered ones that there are even numbered ones. I believe this is because sprockets with an odd number of teeth wear, both themselves and the chain, more uniformly that sprockets with even numbers of teeth. If a sprocket has an even number of teeth, then the same tooth will be engaged by the same pair of chain rollers upon each rotation. This, in turn, leads to uneven wear on the chain and sprocket and a shortened service life for both... as I understand things.
I thought about the above for a good few hours whilst I was away on business someplace else and couldn't see any other, relatively simple (DIY) and low cost approach to my speed dilemma...
As I was originally 'aiming' to replicate the original / standard scoot I decided to settle for slightly improved 45kmh performance and opted for an 11tooth sprocket.
Working out the math on this one from the original formula :
5 x CSR x 0.0714 x 1.45 x 60 = Kmh
CSR = 17/11 = 1.55
=> 5 x 1.55 x 0.0714 x 1.45 x 60 = Kmh
= 48Kmh
...and... the max motor rpm was stated (and seen on the tacho as the 'limiter' cut in) as being 5900
=> 5.9 x 1.55 x 0.0714 x 1.45 x 60 = Kmh
= 57Kmh
So, with a 17tooth sprocket up front (on the motor) and an 11tooth sprocket on the rear (gearbox input shaft) I should expect a top speed somewhere in the region of 48 to 57Kmh.
That was OK. I was 'happy' again... the question though was how to get an 11tooth T8F sprocket onto an overly long, 38mm diameter shaft !!
In the end, the solution was pretty simple, if a little drastic. But, hey, what the heck, I'd already gone way past the point of no return...
Adapt the shaft !
So, I'm off to do just that !!
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Might it be possible to mount a jackshaft in the area of the original engine crankshaft? Though a considerable amount of work, doing so would give you a wide variety of drive ratios.
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Hi Bill822,
Hmm... I think that would indeed be possible but... like you say, work and cost would be major factors here.
Simpler may be just to get a better / more capable motor controller combo. The motor would interest me from the point of view of its shaft fitting giving me a wider range of sprockets. Having said that, I've pretty much locked myself in to the existing motor drive type now 'cos I've started the gearbox input shaft modifications for the T8F / double 'D' sprocket...
If the math is OK (I think it is :o), then the Scoot-ee should be good for an easy 50+ Kmh.
To be fair, I'm digging my heels in a wee bit with this because I so want to make the whole thing on budget - both with respect to time (around 40hours) and cost (circa 800 Euro). If I can get the Scoot-ee on the road with it's DIY-er / do-at-home upgrades , as-good-as original performance and a 30+ Km range for around 800 Euro I will be a VERY happy chappie !! 800Euro is about the same as 2 months London / Paris congestion / low emission zone costs.
If, during trials and subsequently, I find it's been a bum project for whatever reason, I'm consoling myself with the thought that I've learned a HUGE amount and I can either upgrade the motor / controller for the Scoot-ee or transfer the idea to another project.
I've started the gearbox input shaft / gearing works on Saturday and, although busy with the family all weekend, will (all things being equal) finish them today (this morning over a coffee) for a test ride... Then we'll know...
I'll post up my weekend and this morning's work later today (with any luck).
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Having experienced the results of my NOT having done some math (I guess, at the outset, I had just 'hoped' all would be well because it was the simplest solution - not to mention that the conversion itself seemed pretty daunting and I was impatient to start. D'Oh !! ) and having just recently worked out the chain / sprocket ratio I was looking for, I ordered up and received three T8F / double 'D' sprockets; 9tooth, 11tooth and 17tooth.
The 17tooth is for the motor sprocket
The 9tooth is for the rear sprocket along with the 11tooth sprocket should the 9tooth be, as expected, simply too small for the chain / shaft diameter... it IS sold for this chain but maybe not this shaft diameter and I'm loathe to reduce the original diameter of the shaft on the gearbox side of the sprocket. Each sprocket was around was 7Euro, so why not give the 9tooth one a go anyways ?!
So, in steps (always easier for my tiny brain ! ) :
I'm going to need to :
shorten the existing input shaft,
reduce its diameter, creating a 10mm shoulder for the T8F sprocket,
reduce the shaft diameter still further (to 8mm) so that the T8F sprocket fits over it and up to the 10mm shoulder,
cut two flats on the 10mm portion of the shaft to suit the T8F sprocket, ensuring they are 6mm deep - the depth of the sprocket,
cut an 8mm / M8 thread onto the newly created 8mm portion of the shaft,
slide the sprocket into place, followed by a lock washer and then the M8 nut (the lock washer not only helps prevent the nut from backing off but also takes up the 'slack' between the 10mm-to-8mm shoulder and the thread on the 8mm shaft due to the shoulders on the thread cutting die).
When put like that, it all sounded pretty simple but how to achieve concentric faces on the shaft whilst the shaft is still fixed to the gearbox ? I really needed to remove the shaft and lathe it up... but... that's definitely NOT within the realms of your average DIY'er I thought and most certainly outwith my budget to have it professionally done (not to mention that it's outwith the original scope of the project)...
What I came up with was slightly simpler: reassemble and back-drive the gearbox with a drill. So, attaching a suitable socket to the drill and driving the gearbox from the wheel end gave me a rotational advantage of 14:1 (the gearbox ratio in reverse) and the ability to rotate the input side of the shaft just like it was on a lathe ! Well, that was the idea... So, sticking to my step-by-step approach, I :
1: reassembled the gearbox and removed the existing clutch / variable-drive unit for the gearbox input shaft :
2: measured the required offset; the distance between the shaft bearing face and the end of the 'to-be modified-and-threaded' shaft, taking into account the depth / thickness of the sprocket, lock washer and nut (+ a wee bit).
3: attached the drill to the output side of the gearbox and had my 'helpful assistant' on the drill trigger ! And now, cut the shaft to suit. No going back now !!
4: carefully re-measured the offset of the 10mm shaft shoulder and, with the help of a spinning gearbox input shaft (drill and helpful assistant), a grinder (for the initial 'get-me-close' work) and a file and some digital callipers (for the finishing / precision work), reduced the shaft diameter to 10mm (for the sprocket).
5: carefully measured a 6.5mm offset on the newly created 10mm shaft and reduced the shaft end to 8mm, thereby creating a second shoulder for the washer and nut...
6: locked the shaft and filed two opposing flats on the 10mm portion to accept the T8F sprocket.
7: threaded the 8mm portion of the shaft getting as close to the 100mm/8mm shoulder as was possible.I was very careful here to get as close as possible but not to have the die come up hard against the shoulder and thereby damage the newly cut thread. The split / spring washer is here to 'take up' that 'slack'.
8: offer up the sprocket and make any adjustments. This was slow work, you can't add a bit back onto the shaft after taking too much off... slow but sure, testing and measuring all the time.
9: fit the split / spring washer and the nut !!
10: Use a rule for the check the final lateral alignment between the motor pinion and the gearbox sprocket. There is around 15mm of lateral movement in the 4 x motor mountings so final alignment was simple enough.
11: Cut and split-link the chain to suit and then tension in the usual 'alternator-style' way at the motor. In the case of a scoot and particularly in the method I'd selected to mount the motor, there is no 'play' needed in the chain to take up suspension travel. The motor, chain and rear wheel all move on the same swingarm / frame... No idler, sprung tension sprocket needed - one of the clever design features of a scoot's transmission.
All in, from start to finish (once I had the math pegged), this took the best part of an afternoon ! Nice 'n' steady was the name of the game here, like I said, I was very aware I couldn't easily remedy removal of too much of the shaft...
As it happened, all worked out just fine and, remember, I'm an electrician (of sorts) to trade, not a machinist or mechanic ! If I can do it, then anyone can !
I should have done this from the start but feared messing about with the mechanical stuff - just go nice and slow, take your time, better to get a good result and take your time than to rush a mistake... especially as a 'mistake' on the shaft work is not easily recovered from.
That's me for the initial conversion. All-in-all around 37 hours work. The next one would be MUCH quicker (barring any mistakes) IF I was ever to do another scoot - what I'd REALLY like to do is a Kawasaki VN 650 or similar - now that would be fun !
Anyways, I'm off to have some fun and (gently) road-test the Scoot-ee !!
There will undoubtedly be some alterations and additions but they're for another day as is whether this could ever be documented with a view to creating a 'kit' of parts. I'm also keen to make a small video of Scoot-ee on the road after some basic road-tests. Maybe it could indicate the performance, how it sounds and behaves and. . . and whether I feel it was all worth or not...
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...and some other images I couldn't include in the previous post...
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Wow ! :O
So this is an EV grin ! I'm still picking the flies out of my teeth (yeuch) !
I'm not quite sure where to start. I realise this project was only for a 50cc scooter and by many standards it was pretty simply / basic but I am blown away - not by my work but rather by the result; quiet, cheap to run, non CO2 polluting, low maintenance...
Incredible.
It's true, you HAVE to try electric before knocking it and then... well, after a a try, you most definitely won't be knocking it ! :D:D:D
Anyways, I'm a pretty 'picky' kinda guy and, normally, the first to criticise my own work and the results of it so, let's start with the criticisms :
To be fair, at this stage, after 34km on Scoot-ee, I don't have many criticisms :
1: take-off is a little... 'vicious' / quick. There seems to be no gentle / soft-start I guess I'd call it. Just have to be careful when starting off that you're pointing in the right direction. To be fair, it's nothing horrible, just not quite the soft / gentle start I'd have preferred for normal kick-offs...
2: the batteries are hard to remove - I'll re-design them from long'n'thin (20 x 18650 cells long and 4 x cells wide) to short and fat (10 x cells long and 8 x cells wide). The new size is just within the capabilities of Prusa mk3 printer and should allow me to fit 3 (3Kw) (in lieu of 2 - 2Kw) if I want / need to. To be fair, 34km and not dead is better than I imagined... so... 3 packs most likely will not be necessary but...
3: the V / A 'test' meter could be better. I'd like to improve upon this with a coulomb counter type meter or maybe a full screen / instrument panel to replace the one that's there... it's not a 'requirement (especially as I scraped in, just under the 800Euro budget) to be fair but if such a display could be fitted and look good then it would definitely be better.
4: in an ideal world I'd have been able to keep to a belt drive. Much quieter, but really... it's a little like a turbine powering up... not loud or annoying... I'd have simply preferred EVEN quieter !
Having said that...
Top Speed
the top speed is in excess of 60kmh down hill (rev limiter cuts in again at around 65-68Kph) and easily 57kmh on the flat (wind or no wind) VERY happy !
Acceleration
seems more than adequate.
0-30Kmh in 5.1 seconds
0-45Kmh in 9.8 seconds
0-50Kmh in 19.9 seconds
250metres from standing start 21.6 seconds
Definitely NOT blistering but better than stock. It probably didn't help that my mouth was wide open in an electric / ecstatic kind of grin - must have increased drag / resistance ;)
I'm also pretty sure that a Kelly KBL72101X controller would make a huge difference but then it would add an additional 300Euro to the budget ! But... once I receive thoughts from you, more experienced guys, I'd be more than happy now to swap out the controllers for a test... Currently max amps through the controller is 'limited' to 40A - it's just the controller. Loading up the two battery packs through their BMS's and breakers delivers in excess of 75A so... Kelly controller upgrade would seem to be appropriate if I need / want more dazzling performance.
Noise
Impressive, almost none, just a chain 'rattle'... and a turbo-style whine... not bad at all and a HUGE improvement over the original !! I'd still like a belt though. This motor just won't accept a belt very easily...
Again, if I were doing another conversion I would spend more time researching the motor and get something that could handle a belt pulley, maybe with an additional end-of-shaft bearing for less shaft stress... thoughts anyone ?
Having said all the above, I still can't quite believe it all works so well.
I'm monitoring controller temperature (fishtanks style digital thermometer clamped to two controller fins and heat paste. Currently, (just 34Kms) the max recorded temperature is 36'C / 97'F. I think that's OK but, again... thoughts... I'm also going to do some decent hill work this week to test and check controller amps / temperature / volts... EDIT : I should have pointed out that ambient temperature was 19'C here in Britany.
What more can I say ?
Time
Conversion work (give or take a wee bit) : 40 Hrs
Costs
Original RPS Scoot purchase price : 200 Euro
Batteries (2 x 20S4P LiFePo4 / 1Kw ea) : 498 Euro
Throttle, DCDC converter, SSRs : 75 Euro
Cable, Plugs+Sockets, Meter+Shunt : 50 Euro
Fibreglass, paint, clips... : 25 Euro
Total (give or take a wee bit) : 850 Euro
Bear in mind,
I have never undertaken a conversion before...
I am only your standard electrician / electronics engineer...
Granted, I have a pretty extensive set of tools but...
I solder and braze regularly but, although I have a MIG welder, I have less than a full day's welding experience (slightly more now !) ...
I can fibre glass (used to build beach-rescue canoes etc) but there wasn't much to do on this project anyways and anyone can make a cardboard template or two and apply some fibreglass, so...
Tools
90% of this project could be undertaken without any specialist tools; a 'standard' toolbox (spanners, screwdrivers & files etc), a drill, a grinder, a multi-meter and a soldering iron.
The last 10% would involve a welder (stick would be fine, I used a MIG), a method to make up your battery pack(s) or you could buy it (them) ready made, a hot air gun and a glue gun...
Granted, I DO have use of a 3D printer and I have extensive experience with both it and Sketchup BUT neither are absolutely necessary...
Registration
Re-registration in France is all but impossible BUT in the UK, it took less than 30 minutes to arrange, the road tax is zero and the insurance cheaper than the original ICE scooter. Having said that, I live in France and haven't physically done a re-registration BUT I have spoken at length to DVLA (thanks Bob) and various insurance brokers...
I have no idea as to how difficult it is in Germany, Netherlands or the US but, remember there were ZERO frame, swingarm, brake or original equipment mods - all I did was remove the ICE kit...
Cost Justification
As if we need one nowadays to switch from fossil fuels, not to mention the fun to be had during the project and the amount I learnt... but...
All of the work was completed for a total expenditure of (give or take) 1,000 Euro. That includes the original ICE scooter purchase !!! There are quite literally thousands of 50cc / 125cc scooters, mopeds and motorcycles in Europe alone that don't work but could be brought back to life for less than a thousand Euro / Pounds with almost zero running charges ! It might be illegal (strictly speaking) to ride a conversion on the road today in France and, maybe, other countries, but in 12 months, 2 years or 5 years time and as governmental Co2 reduction targets come into force ??? Who knows ?!
Additionally, Low and Ultra-Low Emission Zones are on the increase. Two to three months riding in one of these zones would pay for the conversion.
Charging
Finally, I put an OWL (energy power) meter on the charger last night. The 2 x packs were showing 67V at the start and were fully charged this morning (I think it should only take 4 to 5 hours tops from empty to full) and the meter displayed 1.7Kw of energy at 26cents (0.26 Euro) cost - for 34Kms !!!! Incredible.
Solar
I can't help but get all fired up over this and think I could run for free if I had roof solar - and not much of it at that !! No cost to me, reduced noise, almost zero servicing costs and no Co2 emissions damaging the planet ! What's not to like ?
Next
I guess now, it just remains for me to :
do a lot more tests,
make a video and You-Tube it,
undertake the mods (when I've stopped grinning) and
monitor how Scoot-ee performs over the next couple of hundred kilometres...
RESULT ! Delighted ;D, I think that says it all - I'm converted !!
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Very impressive build 3DRoboGuy. Thanks for sharing your build experience and good luck with the rest of your modifications and any experiences getting your scoot registered. :)
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I've been away and so much has happened since I last read your thread! Congratulations on your successful build.
I am quite impressed with your manual machining. I never would have attempted that without a lathe.
Chain drives are noisy. You can reduce the sound level by covering the motor sprocket and chain completely (fiberglass?). sound will escape from any opening in the enclosure so cover them up.
Yes, bigger motors are the answer to everything once you start playing with vehicles. Sure, that means bigger better controllers, more batteries, and eventually more rear tire replacements ;D
Abrupt starts- Have you checked the function of the throttle potentiometer with a multimeter? Some are quite cheaply made. Perhaps a small resistor in the wire to the controller could help diagnose that issue. If the problem is the controller you are stuck until you get a new one.
You have made this look easy though I know it was not. I look forward to your video. Be sure to post a link here when you have it.
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So, my original Panasonic 18650 cells, as a 20S4P pack in a 20 cells long x 4 cells wide configuration were, it transpired, simply too awkward a shape to remove and re-insert easily.
I designed them this way so that the two packs would lie alongside each other just forward and above the motor in a GRP tray I'd made up. This was all to keep the centre of gravity as low as possible whilst enabling pack removal - to be charged indoors, for additional security and for piece of mind in extreme temperatures. The design should also have allowed the helmet to be stored in the remaining space - there is no helmet lock on this scoot.
All looked good on paper and with mockups BUT, in reality / in use, with all the plastic panels and seat pod back in place, things were just that wee bit too tight; the batteries were very difficult to remove and the charger had to be removed first to enable the batteries to come out (and go back in)... And any helmet, apart for the most basic with no visor, didn't fit anyways (I really should have checked that first ! D'oh! ).
In short, a real pain...
So I looked at ways to re-jig the available space and decided to redesign the long and thin (20 cells long x 4 cells wide) packs into short and fat (10 cells long x 8 cells wide) packs.
The idea here was to put the charger forward in the GRP tray and then the two battery packs, side-by-side, directly under the seat and easy to remove.
Back to Sketchup and a re-design of the plastics that would be necessary for the second attempt (embarrassed face)...
Once I had the design, I dug out the original foam template packs and modified them to represent the new 10x4 configuration I had in mind. I added some additional foam - just to make them slightly oversized / larger than my Sketchup designs indicated (just in case !! ).
The new battery packs were then offered up left-to-right and forward-aft. I needed the charger to fit in as well and was keen to see if I could re-jig in such a way as to let me add a third pack at a later date, if I felt I needed to... As it turned out I fitted the charger in front and across the scoot. The two battery packs fitted neatly in a forward-aft configuration just behind this and... I think... I've just enough space to squeeze in a third pack later on - if required. That was lucky - I really didn't want to have to 're-invent' the GRP tray as well - it's not that difficult but it does take time and...
As it turned out that was the easy part; modifying the existing battery pack configuration wasn't as easy as I had anticipated - mostly because I'd spot welded the packs together - preferring spot welds to solder and never thinking they'd need to come apart (D'Oh !).
Anyways, once I'd opened up the packs and split them at the half way point (2 x 'sub-packs' of 10 x 4 cells) I realised I'd have to disconnected the BMS sense cabling, re-route and reconnect. In fact, as is often the case,, the thinking about doing this was more daunting than the actual doing ! Both packs were re-jigged within the day and ready for their new, 3D printed, enclosures.
The new design has just 3 parts (as opposed to original 5 parts) and is much sturdier; a top, a bottom and the slide in / out face-plate.
Additionally, I decided to try out brass 4mm inserts for the 4 corner machine screws to land onto rather than my 'tried and tested' method of machine screw one side of an enclosure and a matching nut on the other.
The face-plate houses :
the Circuit breaker,
the 2-pin Anderson Controller connector and
the 4-pin Charge socket.
It simply slides into slots on the two enclosure halves which makes wiring it all up really simple.
Luckily, both the Controller cable and the Charger cable were sufficiently long so there were no more mods to be done. I just had to wait for the 3D printer...
So, putting it all together :
I found the best way of inserting the brass threaded 'inserts' was to simply heat them with a soldering iron whilst applying slight downward force. Speaking from my experience, attention has to be paid :
1: not to overheat the insert - it's very easy to loose control of its direction and depth if it's too hot !
and
2: to maintain as vertical a pressure as possible - again, it's really easy to mis-align the insert and, as such, have difficulty screwing up the machine screw later. To be fair, a misaligned insert can be re-aligned later after some heating but it does take some time and weaken the structure / insert's grip on the surrounding plastic (PLA or ABS).
TIP: I found it best to apply gentle pressure with the soldering iron until the insert was around 1/3 depth and then replace the iron with a flat faced tool (like an overlarge allen key) to continue the downward pressure and ensure a flat face on the surrounding plastic mating surface. This way it's not as easy to push the insert in too deep, it's easier to maintain verticality. and the colder mass of the allen key allows the insert to cool faster, thereby minimising insert 'drift'...
Anyways, the finished battery packs look like:
I noted that I was not going to have enough of the one colour to complete printing the packs so decided to print one side of each in silver and the opposing side in black ! Seems to work !! I also wanted to ensure as little 'stress' on the inserts as possible, so taped up the packs (over the insert area) at each end. If I was printing the packs again, I'd most likely have 6 inserts / matching M4 x 35mm machine screws but...
The new packs dropped back into Scoot-ee without any issues at all. All-in-all a successful rescue from my first poor design. That was a bit of luck.
The downside ? Whilst there appears to be sufficient room for a 3rd battery pack (just) there is no longer room for my lunchbox !!
Anyways, new batteries complete. Onto the other mods / improvements...
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I definitely seem to have a problem with my images. I have tried to keep them small but too small and they're blurry, too big and I can't include them all. My apologies... Maybe someone could give me a tip on how to achieve a middle ground ?
Anyways, some more...
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I'll limit myself to just the final things now...
There's more info and images on my website : www.ianwatts.online/scoot-ee
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Well... I thought I should make a *quick* update.
Scoot-ee has now completed more than 500km since going back on the road after the conversion to electric.
Nothing major to report (except the previous battery re-configuration work).
A video can be found here : https://youtu.be/4QgF20aDRrw
This was my first foray into forums, my first scoot conversion and now this is my first YouTube video (needless to say, I'm extremely anxious ! ) Be gentle folks !!
It does go a long way to proving though - if I can do it in my garage, so too can anyone else with a mind to do so !
Anyways, on a not so great a note, some of the in-use problems I had :
1: SSRs : I decided to use SSRs (Solid State Relays) to handle the power switching on Scoot-ee. I encountered a few issues here :
SSR's dislike back EMFs and spikes and, like any other 'switch' they can't control inrush current (like when connecting the battery to the controller). There are also tons and tons of el-cheapo Chinese copies that are simply not up to spec / masquerading as 60A units when, in fact, they're only 25A or 30A internally !! I'm not making this stuff up, I actually stripped the third failure down - one 25A FET... That was it !! VERY annoying. (If I get time, I'll make a post about my work with this too).
The inrush current is handled in many different ways. For me, being an electronics sort of chap, I decided to go down the NTC / PTC thermistor route. I contacted those really nice guys at Ametherm (Canada) and was re-directed to their European (UK) office. To cut a long story short I found (thanks to Tony Chedester - Canada and Eleonore Hofmann - UK and some formulae they supplied me with) that the AS32 5R020 does a great job providing inrush current limiting across the Hi-V (Controller) SSR as did a chunky 100v, 6A diode in reverse across the SSR to deal with back EMFs to the battery. Between these two components and a 'real' (not cheap Chinese copy) 100A DCDC SSR I have had no more inoperative SSRs for over 400Km now. Result !!
2: Charger : I found the charger (much like the controller) really didn't 'like' the instant it was connected to the on board batteries. Each time a connection was made a noticeable electrical 'crack' could be heard. A temporary way around this issue was to ensure the charger was connected to the mains and 'On' before connecting it to the batteries but... that was 'fiddly' and prone to error (forgetfulness). Anyways, once again, Ametherm and their formulas and data sheets came to the rescue. Once I'd fitted a suitable, in-line, inrush current limiter between the charger output and the batteries, the problem went away - permanently. Another Result !!
3: Batteries : I had initially designed my batteries to be 'long and thin, siting them above the motor (low centre of gravity etc), 20 x 18650 cells long and 4 cells wide (as per the previous posts). In fact, by the time I'd refitted all the fairings / seat panels, I found it almost impossible to remove and refit the battery packs. A redesign was required !! I redesigned (Sketchup) the packs to be 10 cells long by 8 cells wide. No mean feat re-jigging the packs / spot-welded connections... but... a days work and two days 3D printing time later, I now have new 2 x re-jigged packs. MUCH better. An additional unexpected 'plus' - the battery pack re-design would appear to enable me to fit 3 (as opposed to the designed-for 2) battery packs within the available area below the seat, the shorter / squarer batteries fit best further aft... which means I used the now 'spare' space ahead of them for the charger which no longer sits on a shelf above them. I've discussed all this in a previous post.
All the above is neat and really works out well - day-to-day charger access isn't really needed - however, to the 'negative' bit - relocating the charger forward of the batteries basically 'hides' it away which means the red (charging) and green (charged / finished) LEDS are no longer visible ! So... I now need to add a remote / more visible Red/Green charging/charged LED. I'm currently thinking about a suitable site / method of doing this...
4: Range : There are two 20S4P packs fitted. Range though is (depending upon use) between 25km and 38km. 25km when driven REALLY hard, two up. Much better, up to 38km without any run-out-of-juice dramas, if my wife is in control or I select the 'Lo' Speed setting (you may remember, I wasn't sure why I would need 'Lo' but... I added the Hi/Lo switch some weeks ago) !!! I'm sure this could be bettered still BUT youngsters feel the need for speed and it doesn't really matter how often I tell them, the throttle grip appears to be a two stage switch for them (with no in-between) off / stopped and on / full speed !!!
5: Coulomb counter / Volt/Amp meter : We've learned to 'take it real-easy' and 'limp' home when the displayed voltage drops below 68V on the level and with no (or very little) acceleration ... Still 30plus Km for a 2Kw pack (around 30cents a re-charge) is brilliant ! I really do need to get onto that coulomb-counter... My logic here is to design an Atmel microprocessor based board that monitors voltage and input (charging) / output (motor / lights etc) current. I'm thinking a small micro-processor based board (once programmed / configured) should be able to display remaining Amps and, therefore, remaining Km. Either on a dedicated display or, this summer's job (if nothing else more urgent pops up) on the existing fuel gauge. When the gauge drops into the red, it's time to head for a recharge !!
Anyway, like I said above, I did create that Scoot-ee video (my first ever video) and it's here : https://youtu.be/4QgF20aDRrw
I have thought of doing a few more, based on each of the major steps during the conversion but the vid took me a day all-in and, whilst I'm willing to spend time creating and posting them, I'd only really feel comfortable doing so if someone feels that they may be useful... so... I'll wait and see what the responses to the video are like.
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I am glad you came back to tell us how it was working for you. Very glad to see it running well. I have many projects on my list this year but I have added one more. I have been afraid to just jump in on an electric bike conversion but your clear log of your build has settled my nerves. Other things must be finished first though.
I've used NTC thermistors to help control inrush on strings of DC motors and a delay on make relay to drop the thermistor out of the circuit after startup to reduce voltage drop and especially to reduce heat once running.
For posting larger images I upload to Imgur(dot)com (free to use) and post the link like this.
https://i.imgur.com/osnAwBO.jpg