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[McRat]

I don't understand how both versions have the same top speed, same torque, yet different horsepower.

Can somebody explain why the second battery increases HP but not torque?

Is the second battery that useful in the dirt for more than just range anxiety?

Sorry for all the questions, but I want to know exactly what to expect when I buy it, and whether is has a limitation that I'm not aware of.

[rayivers]

The second battery maintains full torque to max motor rpm, while the single battery gradually reduces torque above 40mph or so. Below 40 my 2.8 accelerates slightly faster than my 5.7  (40+ pounds lighter), then the 5.7 just walks away from it.

Ray

[McRat]

Thanks!

So for technical areas, removing the front battery is the ticket?

How hard is it to remove batteries?

Are both batteries removable in the field?

[rayivers]

I like using the rear battery in the dirt bike (which keeps the front end light) and the front battery in the street bike, which keeps the front end down and also shows off the motor.

Both batteries are field-removeable.  If you run one battery, you'll need the battery plug that should be Velcro-ed to the frame above the front battery bay, near the horn.

To take out the rear battery, obviously first unlock & remove the RH frame rail, then I hook my fingers around the LH bottom and rear frame rails and push hard on the bottom and side of the battery simultaneously with my thumbs - usually it pops right out.  The front's the same, except the front frame rail isn't as accessible so it's easier to use both hands on the bottom frame rail and push a little higher on the battery case.  The idea is to not cock the battery during removal, and push it straight across the battery bay.

Ray

[protomech]

I don't understand how both versions have the same top speed, same torque, yet different horsepower.

Can somebody explain why the second battery increases HP but not torque?

Is the second battery that useful in the dirt for more than just range anxiety?

Sorry for all the questions, but I want to know exactly what to expect when I buy it, and whether is has a limitation that I'm not aware of.

Yes.

Torque is proportional to motor current. Until you hit field weakening, RPM is proportional to motor voltage.

The motor controller converts battery voltage in the range of 85-115V DC to AC at the appropriate motor voltage, which could be 0-100V AC depending on RPM. Simplification: at low RPM this may mean the motor controller is driving the motor at 400A @ 5V RMS (2 kW) but is drawing from the battery 20A @ 100V (2 kW again).

The motor controller has a maximum phase current it can supply. This is the torque limitation for the motor. It's why the Zero SR has more torque than the Zero S: it's using a larger motor controller rated for higher current. Same motor, basically, different controller.

Batteries also have a maximum current they can supply, which also acts as a power limit. This is approximately a 7C discharge rate for the Zero batteries, or 175A per module producing about 20 kW.

At low RPM, motor torque is limited by maximum current of the motor controller. Per the example above, the motor controller can output pretty huge currents at low RPM & motor volts with only a little current draw from the battery!

At high RPM, motor torque may be limited by the maximum current the battery can supply to the motor controller. If the ~100V battery maxes at 175A, then if (for example) the motor controller needs 60V RMS across the motor then it can only provide about 300A AC to the motor. A second module would double the maximum available current from the battery, allowing the motor controller to continue to operate and provide maximum torque (at about 400A for the Sevcon Size 4 in the FX).

[rayivers]

Great explanation - thanks!

Would there be any advantage to upgrading to a size 6 controller with a single 2.8 module and 75-5 motor?  I've been wondering about this for a long time.

Ray

[Cortezdtv]

You cannot use a size six with 1 battery period


Zero won't even do it with less than 3 "fx bricks"


Message me if you want to size six a 2 brick fx; it turns into a wheelie 0-70 freaking monster

Will walk away from a fx easily with the bigger controller

[Cortezdtv]

You cannot use a size six with 1 battery period it will destroy the battery on first or second pull of the battery. The size six with a 2 brick fx, is at the extreme limit of what the batteries can actually handle. With the 13 batteries you would pop the fet board in the batteries, the 14s have a contactor which is more robust which may last longer but.....

7C per cell is big draw
So 14C per bike
 I'll have to log into bike and look but I believe last settings were battery cutouts at 20ish C so I gave about 7C or 1 extra cell worth of draw on the same 2 batteries .   Once you ride a bike with that much instantaneous torque everything seems slow.

Zero won't even do a size six with less than 3 "fx bricks"


Message me if you want to size six a 2 brick fx; it turns into a wheelie 0-70 freaking monster

Will walk away from a fx easily with the bigger controller


Personally I've had a soft spot for the size four (stock controller on fx) turned up a which is a mmx tune with the 757 motor, this you can run as a 1 brick bike safely and it is also a very light powerful bike.  The difference between the acceleration from mmx to size six is incomparable it's a bigger jump than going from a fx 1 brick to a mmx 2 brick; honestly I would say as far as a SR. It is the "same/similar" tune on a 300 lbs bike vs a 500-550 lbs bike.   I mean that's basically the weight of my bike difference!!!!!

[rayivers]

Thanks very much for the info! Your 2nd reply answered some questions I had about battery limits.  Destroying my battery would definitely ruin my week.   If battery capacities increase greatly - and after my warranty expires - I may well be interested in the size 6 controller upgrade and will PM you about it.  What is the difference between the MMX and FX controller programming?  Does the MMX controller pull harder on the battery(s) and/or have a different throttle curve?  I'm very interested in anything to do with the MMX, in the US buying one is like trying to get an M61 (just kidding, sort of).

Right now, my 'MX' with the 12/71 sprocket setup is just about perfect power-wise for the trails I ride on near home, as long as the charge is above 80% - below that, the bike gets tired faster than I do, which is really saying something these days.

I've tried running two bricks off-road, it just doesn't work for me - it seems like I'm pushing through the dirt rather than floating over it, and the bike feels top-heavy compared to one battery.  At 228 lbs, the 'MX' feels fairly light to me despite being the heaviest bike I own, and is definitely the best-handling dirt bike I've ever ridden. Maybe it's a center-of-gravity thing, but whatever it is, the bike feels responsive and stable, which is way cool.

Ray

[Cortezdtv]

Completely understand everything you said!!! Especially about 2 brick being heavy for dirt


Honestly if you do lot of dirt riding the mmx is going to take the best of both worlds
You will get the bigger motor which will greatly improve acceleration down low and up high but also to me give you more "control"

Yes it takes more energy to move the bigger motor in the same fashion so it has a little less range.

 I never notice and I would also like to point out that it is significantly easier for the bigger motor to propel the bike.


 So in ahilclimb that you have had to stop halfway through for whatever reason,
On the fx you lean forward and pin it, it will move forward and slowly reach the same point as the throttle, it's playing the "catch up game".
The mmx with just the bigger motor won't have new as much"catching up to do" and is much snappier like a "two stroke" compared to 4 stroke ( only equal comparison of acceleration I can think of).  Yes you get the acceleration on the bottom with electric and top with gas but the gap from 2 stroke to 4 stroke is similar from 1 motor to the other imo.  The size six takes that same theory to the limits.....
For me it was like the first time you get on a 250 2 stroke. Barely anything then it comes on like a bat out of hell.... Imagine 2x that from a standstill

I know what your saying about the mmx,   It is buying a legal m61 LOL something's are like teeth pulling

For instance I live in Santa Cruz it cost me less than 3$ in my tundra to get to zero and back( even getting 12 mpg yes I do pull 5000 rpm a getting on the freeway).  It cost 10-25$ to drop ship a part to me from zero going through some dealership..... It would still cost me less if I paid the "Msrp" went to pick the part up and then still giving the dealer his 33%.....yes we are arguing over small numbers, but I can guarantee 90% of the people who bought zero bikes ran the number for months to find out if it was woth spending the money, their demographic is EE's or EE type people, electric enthusiasts; tipiically well educated people who run the numbers.....
There new company policy is "go to your nearest dealer" they are the manufacuter; furthmore a dealer of new and used bikes. Having bought most of my collection of zeros directly from them, there at their dealership and showroom, I would think that they are still a dealer that sells motorcycles.....they would support people who bought bikes local..... It also gives me a reality check as if I did not know so many people who have worker there and do work there, would they help me with parts....like if I was in Australia or Europe.

It should be easy to buy upgrades parts, motors controllers etc, it's all money in their pockets.

Things in customer service are getting better, I'm sure in reality they are somewhat understaffed as I see them hing temps constantly and everyone who stops and talks to me has had a brother cousin for friend work there, part of it is the nature of the business, part in my opinion could be mistakes

[rayivers]

Does the 75-7 motor give more power with one 2.8 battery? Both my motors are 75-5, I figured that was as good as it gets with one brick?  I guess I really should think to the future.  Maybe some day I can get a 75-7  motor / size 6 controller / 5.0? brick upgrade as a single deal, then sell my old stuff for big bucks on the Zero used-parts market (not).

I hate the "catch up game".  If one of my ICE bikes did that, I wouldn't ride it again till it was fixed.  I find that if I only twist the throttle halfway the bike works much better, and I also notice the lag a lot less in the dirt, maybe because I'm busy staying upright and stuff.    The amount of power you're describing seems like way too much for these tight CT trails - I'd be peeling myself off trees.  The KTM 200 I rode once was trench-digging wheelying blood sport.

Does Zero have an actual parts (as opposed to procurement) department?  My next order will be my 6th, and while I've gotten nearly everything I ordered, sometimes it took a few tries.  The prices seem quite reasonable for the most part, though.  It must have been nice to just go to the factory, but it sounds like those days are coming to a close - it must have been the same way for Honda et al in the beginning.

Took the bike out today, and made it back before the rain - ran great, tracks so straight thru all sorts of nasty wet crap under the leaves.  The chain pulled in a 3' underwater sapling, I just stopped and cleared it - don't think a belt would have allowed that (but I still want to use a belt !!).

Ray

[acacia1731]

I finally got some more time in the dirt yesterday with my FX, and have found all of the above comments to be right on.  One (rear) battery is the way to go, lighter but not noticeably weaker at off-road speeds.

I also found that I dislike the power lag.  On small stream/log crossings, I find that I need to plan ahead more and blip the throttle 1/2 second earlier than with my 2-stroke MX bike.  The FX can float the front wheel over, but since I switch back and forth between the two bikes, I'm positive that I'll occasionally forget about that timing difference and end up going over the bars.  Similarly, on hill climbs, I find that I grab extra throttle during that 1/2 second delay, thinking I need it, but then I lose traction when the power finally catches up.  I think both of these are just learning curve issues that I could easily get used to IF they weren't so different than my gas bike.  Not deal breakers though, just different.

On the other hand...  There were also several times when l found myself desperately (and needlessly) kicking down with my left foot when braking hard coming into a corner (trying to downshift).  ;-)

[rayivers]

Here's 3 things I did that nearly eliminated the 'lag' (I don't even notice it anymore):

1) Domino throttle (comes on quicker)
2) Gearing down (12/71 sprockets)
3) Setting a 60mph top speed in Custom mode (which seems to change the entire 0-60 throttle curve slightly)

Each one separately didn't have a huge effect, but the combination is a real improvement.

Ray

[acacia1731]

Thanks for the list.  I'm curious to try the 60mph top speed setting ASAP, to see if I can tell a difference.

The Domino throttle is VERY tempting based on your other posts, but the installation (wiring) hassle may keep me away.  If they had a plug-n-play option for Zeros, I'd probably get one today.