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Author Topic: Solar charging  (Read 1502 times)

pacificcricket

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Solar charging
« on: March 01, 2017, 02:04:39 AM »

I know this has been discussed before, and dismissed as a valid approach, but there are some interesting improvements regarding solar panel tech.

This is currently on sale for $149 after coupon : https://www.amazon.com/gp/product/B01DXYNGA0/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=AY5XLL1NQPR7O&tag=tbdirect-20&ascsubtag=0206f078-6967-44ac-93c2-1cef42661020

It is 100W with dimensions of 43.3 x 22.4 x 0.1 inches and slightly under 5lb of weight. Let's say one connects 9 of these in series and then
two of these in parallel for combined 108V and 1800W. Considering that would be DC, and can go straight into the battery via AUX port,
would it get us close to 4 hours of charge time ? Would additional charge controller be needed, or BMS can take care of that ?
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Shadow

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Re: Solar charging
« Reply #1 on: March 01, 2017, 02:34:08 AM »

I'd settle for something I could roll up that would get me 30mi of range for 2-days charging, i.e. for desert trips.
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pacificcricket

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Re: Solar charging
« Reply #2 on: March 01, 2017, 02:36:56 AM »

You'd need at least 9 of those panels connected in series to get the right voltage. That would be theoretically 900W, close to what internal charger is producing. Would be a fairly small package though, under 50lb.

Edit: well, actually they say the panel produces 18V, so perhaps 6 panels in series would suffice for the correct voltage.
« Last Edit: March 01, 2017, 03:10:04 AM by pacificcricket »
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Erasmo

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Re: Solar charging
« Reply #3 on: March 01, 2017, 03:43:05 AM »

I'd settle for something I could roll up that would get me 30mi of range for 2-days charging, i.e. for desert trips.
A few of these and you're good to go:
http://www.powerfilmsolar.com/products/?fm167200_120w_foldable_solar_panel&show=product&productID=271514&productCategoryIDs=6578,6579
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pacificcricket

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Re: Solar charging
« Reply #4 on: March 01, 2017, 03:51:45 AM »

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Shadow

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Re: Solar charging
« Reply #5 on: March 01, 2017, 10:49:59 AM »

The objective is a small enough package for travel, and probably a weight limit, while still being able to put a charge on the battery.

I have two 62W panels from Global Solar. They pack down really small. Open circuit voltage is about 28VDC each. If I *had* to, what kind of boost conversion controller could I try to charge the ZF13.0 pack?
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pacificcricket

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Re: Solar charging
« Reply #6 on: March 01, 2017, 11:22:02 AM »

The objective is a small enough package for travel, and probably a weight limit, while still being able to put a charge on the battery.

I have two 62W panels from Global Solar. They pack down really small. Open circuit voltage is about 28VDC each. If I *had* to, what kind of boost conversion controller could I try to charge the ZF13.0 pack?

DC to DC upconverter can bump up the voltage, but from what I understand they're not super efficient. It would probably be better just to add two more panels, so you'd have 248W at 112V.

I've checked the specs, they seem to pack small, but are fairly heavy in comparison (3lb) and are extremely expensive, $955 here :
http://www.impactbattery.com/global-solar-62-watt-desert-camo-foldable-solar-panel-p3-62.html

As much as it is tempting to have something that folds that small, it's not necessarily the requirement. Those that I've linked above are just a bit over 40 x 20 inches, and are semi-flexible. While it would be a bit bulky, it is still possible to carry them on the back of the bike with tail rack installed.

Also, that same company has 50W model which is roughly 24x24x0.1 inches at 2.6lb. They're just not as cost efficient.
Six of those in series gives 300W at 108V, 15lb and under $800.

$105 here :

http://www.gearbest.com/power-banks/pp_503468.html?wid=27&currency=USD&vip=760153&gclid=CjwKEAiA3NTFBRDKheuO6IG43VQSJAA74F77Wp-cXcHNMnycu5Z0EcWAljWxmtqwTGv8HNVSGSUb8BoC4nHw_wcB

Still, I'd like to see somebody comment on the electrical side of the question. How can we hook that stuff up to the battery ? Any concerns over max current ratings on the panels ? Any additional regulation required ?
« Last Edit: March 01, 2017, 11:27:42 AM by pacificcricket »
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Electric Terry

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Re: Solar charging
« Reply #7 on: March 01, 2017, 11:36:21 AM »

The rated wattage is about half what you will ever see.  And voltage will drop based on the sun coverage.  I would say get enough in series to get about 200 volts.  Because sometimes with partial shade you will have much less.  If the voltage ever goes below pack voltage you will get nothing.  But even in full sun at 200 volts, your line voltage will always be within a volt of you pack voltage.

I think it would be possible to charge a Zero in about a week if you were camping and carried enough roll out flex panels.

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pacificcricket

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Re: Solar charging
« Reply #8 on: March 01, 2017, 12:14:39 PM »

The rated wattage is about half what you will ever see.  And voltage will drop based on the sun coverage.  I would say get enough in series to get about 200 volts.  Because sometimes with partial shade you will have much less.  If the voltage ever goes below pack voltage you will get nothing.  But even in full sun at 200 volts, your line voltage will always be within a volt of you pack voltage.

I think it would be possible to charge a Zero in about a week if you were camping and carried enough roll out flex panels.

How would you connect them to the bike though ?
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wontuan

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Re: Solar charging
« Reply #9 on: March 01, 2017, 12:38:51 PM »

Former solar engineer who now works on battery tech stuff here.

I have helped charged Zero monoliths from some solar panels before and I am currently doing another setup where I have some big panels charging batteries that I use to charge a Zero nightly. Here are some things you want to consider before attempting to charge batteries via solar panels:

1) Solar panel ratings are always optimistic, I know cause I used to work on solar modules.

2) The output power isn't a continuous rating, you will see that the panels output peak power around 11am - 1am depending on your climate and how bright it is. Hot temperature decreases power output.

3) If you don't have an MPPT controller then you aren't going to get one then your efficiency will suffer a lot. The panel's behavior is defined by it's IV curve and there is a point on that curve where it produces the most power. This is where the MPPT controller will try to keep it at. For example if the panel has a Vmp (the voltage where it produces the most power) of 17.8v and your battery can be any where from 90v to 116v and you want to have 9 panels in series, at 90v each panel will be at 10v (assume they are balanced) which is far from their the 17.8v they should be at. At 116v they would be at 12v which is still far from the 17.8v. It might be more efficient to get an MPPT controller that outputs 120vac and just use your onboard charger.

4) You need a disconnect system, meaning when the voltage gets to 116v the panel better stop providing power or else it will over charge the cells. The BMS will open the contactor some where after 117v but opening a contactor under load stress the contactor.

5) Also make sure you have a way to prevent the battery from dumping current in to the panels. Yes this happens and the panels really don't like it. Just put a nice outdoor rated blocking diode between the panel and battery. The diode will always be conducting and producing heat so you got some power lost there and you have to make sure the diode can survive the constant stress and heat.

There are other things to consider but I don't want to get into this unless people ask for it. I am not trying to discourage people from using solar panels to charge things, in fact I do it myself and I have helped other people do it. But the I am fortunate to have lots of batteries and lots of panels so efficiency isn't a big deal for me. Solar technology is moving pretty fast but it will still be awhile before we get a  small and simple solution that will charge our bikes within a day or two. I wouldn't recommend any kind of camping charging solution unless you plan to be charging for 1-2 weeks. Home charging solutions aren't super hard. Just make sure you are being safe and have an electrician or someone who knows what they are doing look at it. For most people I would recommend connecting panels to an MPPT controller that outputs 120Vac and using the onboard charger because it's safer, simpler, and probably more efficient then doing DC-DC charging.
« Last Edit: March 01, 2017, 12:47:15 PM by wontuan »
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pacificcricket

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Re: Solar charging
« Reply #10 on: March 01, 2017, 08:59:55 PM »

For most people I would recommend connecting panels to an MPPT controller that outputs 120Vac and using the onboard charger because it's safer, simpler, and probably more efficient then doing DC-DC charging.

While it would be pretty straightforward to go the AC route, what would happen if your production is less than the draw of onboard charger ? My understanding is it's about 1.3kW. That's quite a few panels to haul around to get anywhere near that output.

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Erasmo

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Re: Solar charging
« Reply #11 on: March 01, 2017, 11:17:56 PM »

There are other things to consider but I don't want to get into this unless people ask for it. I am not trying to discourage people from using solar panels to charge things, in fact I do it myself and I have helped other people do it. But the I am fortunate to have lots of batteries and lots of panels so efficiency isn't a big deal for me. Solar technology is moving pretty fast but it will still be awhile before we get a  small and simple solution that will charge our bikes within a day or two. I wouldn't recommend any kind of camping charging solution unless you plan to be charging for 1-2 weeks. Home charging solutions aren't super hard. Just make sure you are being safe and have an electrician or someone who knows what they are doing look at it. For most people I would recommend connecting panels to an MPPT controller that outputs 120Vac and using the onboard charger because it's safer, simpler, and probably more efficient then doing DC-DC charging.
I agree that this is still a pioneering phase, Toyota an Tesla are the only one who have something in the works right now, and that is more of a ''Hey we have a glass roof anyway, might just as well shove some cells between the layers.'' product.

If you already have a Vetter fairing on your bike you could do a super long ride on PV only today:



Stick 2-3 high power flexible panels with smart stringing options on the tail and you should be able to squeeze out a few extra km per leg and there is plenty of room in the tail to store flexible panels like in the starting post. It will probably take some time to do a USA coast to coast or something but it is totally do-able today for the first pioneer that wants to make a point.
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BrianTRice

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Re: Solar charging
« Reply #12 on: March 01, 2017, 11:29:19 PM »

Marking this for a wiki article since the topic is ongoing and worth tracking as it becomes more feasible. We need a similar article for household power backup.
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pacificcricket

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Re: Solar charging
« Reply #13 on: March 01, 2017, 11:51:15 PM »

I agree that this is still a pioneering phase, Toyota an Tesla are the only one who have something in the works right now, and that is more of a ''Hey we have a glass roof anyway, might just as well shove some cells between the layers.'' product.

If you already have a Vetter fairing on your bike you could do a super long ride on PV only today:



Stick 2-3 high power flexible panels with smart stringing options on the tail and you should be able to squeeze out a few extra km per leg and there is plenty of room in the tail to store flexible panels like in the starting post. It will probably take some time to do a USA coast to coast or something but it is totally do-able today for the first pioneer that wants to make a point.

That's not what I had in mind. The goal is not to charge the bike from solar at all times, but to charge it when it's parked by deploying the solar panels.

I was thinking something like making a solar blanket by threading a paracord through the gromets on the panels, and attaching that blanket to the handlebars and tail on one end, and to ground stakes on the other end (trying to get some 30 degree angle). The other option would be to use some kind of collapsible / folding poles.
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Erasmo

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Re: Solar charging
« Reply #14 on: March 02, 2017, 12:27:31 AM »

The possibilities are more or less endless in how you want to rig it. The blanket should work but you could also just lay it on the ground.

This thread reminds me of a solar moped that has been on the internet for ages:

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