Can e-bike batteries be charged with solar panels?

Jkoll

New Member
Has anyone tried to charge e-bike batteries with portable solar chargers? I am thinking in the context of extending one's range for camping/fishing multiday trips.

Thanks!
 

mrgold35

Well-Known Member
This seems it would work and it can charge more electronic devices, a lot smaller to carry, has a internal battery to store extra power, can help cook your food, keep you warm, works day or night, sunny or cloudy, 5v 2 amp USB output, and can work in any weather. Just need to figure out what type of USB to power adapter to charge the battery.

BioLite: https://www.bioliteenergy.com/products/campstove-2

biolite II.jpg
 

raymann112

Member
I have a BioLite and it's actually great...but not for charging devices. It takes forever to charge a cell phone, much less an ebike battery. The thermoelectric charging is more for powering the internal fan to get a hotter, cleaner fire. What little power is left is used to charge it's internal battery to charge your cell phone. I don't use it and just bring a battery bank, I actually don't even use the biolite unless its for a multi day trip with a basecamp, usually I just bring a gas stove.

If you really want to charge an ebike battery in the backcountry, there are small <30lbs gas generators with built in inverters that can run for hours on a single tank. They're also pretty quiet. This was just a quick search but if you look around you might be able to find something better.

http://www.homedepot.com/p/Honda-1000-Watt-Super-Quiet-Gasoline-Powered-Portable-Inverter-Generator-with-Eco-Throttle-and-Oil-Alert-EU1000T1A/206192043
 

dogdad

New Member
Has anyone tried to charge e-bike batteries with portable solar chargers? I am thinking in the context of extending one's range for camping/fishing multiday trips.

Thanks!
I would like to know this also ! There must be some way to do it ,.
 

Denis Shelston

Active Member
It is a complex question.

Generally speaking I would say no.

But, if you're willing to spend some money and deal with large size panels, it's possible.

Most solar panels only put out under 20v, on a very bright sunny day that is, as they are designed to charge 12v batteries. Panels are connected to a charger controller or MPPT, you would need to boost the voltage out if your panels are to charge an ebike battery, most are 36v or 48v. These MPPT are relatively expensive, $300+. If you have a 48v ebike, you need 52v to charge. Under the best of circumstances it would be somewhat difficult to fully recharge an ebike depleted 48v battery under 5-6 hours of Full sun. You would need large panels, probably 2 x 100 Watts, 2 x 4 feet each, these are probably in the $250 range. Yes, portable, pliable and folding, are also available but much less efficient, they are really expensive.

You would have to charge during full sun, not use the ebike for a while. Another challenge on trips...

Food for thought.
 

Alex M

Active Member
In a nutshell - bad idea.
It will take forever, or the panel will have to be huge like in that video.

Carry a charger. Whatever "multi"-day those trips are, you will inevitably stop in some village to refill on food and water - and then there will be a source of electricity.
Or, if "multi" doesn't extend over 3-4, - carry another battery.

That stove-charger is mere 3W, btw. To charge 500Wh = 160 hours of burning.
 

Finist

New Member
Considering how big such panels look - do you wonder if it's worth it? Of course, it's tempting to recharge the bike during the ride, but to carry a rather large, and also fragile, panel that still can not fully charge the bike, seems weird. I use solar chargers, but these are the most common models, for recharging the phone, camera, etc. In this case, they justify themselves. Besides, do not forget about the charging time, in my 36V 8.7Ah bicycle battery, that it would be successfully charged, the current output on charging should be appropriate, and the maximum which can be found in stores is about 27v, in fact, my battery is even will not be charged.
My opinion, the idea is good, but it does not make sense. (Although if you travel long distances as in the first video, using solar energy to make your battery work much further, it makes sense)
But even if you travel long distances, I think it's not worth buying such a thing, it's better (and cheaper) to do it yourself. Since I enrolled I found a useful guide from one of the e-bike owners who tell how he built his solar recharger at home, a rather entertaining article.
 

Mr. Coffee

Well-Known Member
One of the ugly challenges, aside from needing large panels, is that since most ebike chargers run on AC power, you would also need an inverter.

From my standpoint it is almost heartbreaking that you need to convert the perfectly good DC from a solar panel into AC and then convert it back to DC to charge the batteries. This also can produce a huge efficiency loss, sometimes as much as fifty percent. And even a two or three hundred watt inverter is a substantial amount of extra weight..
 

Finist

New Member
One of the ugly challenges, aside from needing large panels, is that since most ebike chargers run on AC power, you would also need an inverter.

From my standpoint it is almost heartbreaking that you need to convert the perfectly good DC from a solar panel into AC and then convert it back to DC to charge the batteries. This also can produce a huge efficiency loss, sometimes as much as fifty percent. And even a two or three hundred watt inverter is a substantial amount of extra weight..
Is it possible to do without this loss? What would "the good DC from a solar panel" immediately come on the battery, without conversion to AC? We're not talking about "store" models, but about what you could build yourself.
 

Mr. Coffee

Well-Known Member
Is it possible to do without this loss? What would "the good DC from a solar panel" immediately come on the battery, without conversion to AC? We're not talking about "store" models, but about what you could build yourself.
Well, if you took apart your ebike charger you'd find a rectifier (that converts wall outlet AC to DC) and some charging logic that makes sure you don't overcharge the battery. If you can match output voltage on the rectifier (what the actual voltage would be depends on the design of the charger and to a lesser extent the voltage of the batteries being charged) you could theoretically connect your solar panels at that point and charge just fine. With the caveat that you certainly are voiding your warranty and I'd want a fuse or DC breaker in the connection from the solar panel to avoid a fire or explosion.

You can't avoid loss from conversion of DC to AC and vice versa. Good, modern inverter designs running close to capacity have efficiencies in the 80 to 90 percent range. So an 8kw inverter can reasonably deliver 7200 watts from an 8kw array. Bigger inverters are generally more efficient. The catch is that you have to do the conversion twice (once from DC to AC and then back again), so that 80 percent efficiency is really around 64 percent in the most optimistic case -- and keep in mind that the people designing your battery charger probably cared very little about the efficiency of the rectifier, as you are probably only talking about pennies worth of electricity anyway. In practice I think you'd be damned lucky to get fifty percent efficiency with an inverter. Again, the small camping inverters are generally quite a bit less efficient than the larger ones for home solar. You also want to be extremely careful charging in the field since the waste heat even from a dinky 500 watt inverter could easily start a fire in pine needles or dry grass.

Another thing to make you paranoid is that the rated output of a solar panel is for a given temperature, usually 20C. In colder temperatures a given panel or array will produce more power. Especially for larger panels and larger systems this can get quite exciting. That is one additional reason you'll need a DC breaker in that circuit.
 

Ann M.

Well-Known Member
@Mr. Coffee, the component that you have to have is called a controller. It modulates the incoming watts from the sunlight through the panels to prevent high or low voltage issues and also moderates the charging of an external battery if you have another battery as storage or for direct charging. Just running an inverter is not going to be adequate or safe.
 

Mr. Coffee

Well-Known Member
@Ann M., that is correct. I was thinking that most inverters suitable for this application (e.g. https://www.rvautoparts.com/Zamp-Solar-ZP600PS-Inverter_p_14935.html?gclid=Cj0KCQjwiqTNBRDVARIsAGsd9ModCXsISv9OTwOxPFGqo49_XV1-KKyVg_hIeGkdYvXbDXLdLQ3ZaywaAgepEALw_wcB ) already have the voltage-limiting required to avoid disaster. I probably should have emphasized that you'd want an inverter with charge-controller circuitry rather than carry around another box of electronics.

My own suspicion is that you need to be 100x worried about over-voltage/over-current situations (one more reason that I heartily recommend a DC breaker or two for this application). The most likely result of an under-voltage situation is that the battery won't charge, and the worst-case scenario is that you might somewhat shorten battery life.
 

Kapt Irk

New Member
Theoretically, a good quality 12 volt, 20 watt, mono-crystalline solar panel will produce approximately 14 volts at 1.3 amps (under load), so if you series-wire up four 20 watt panels, you'll have approximately 55 volts at 1.3 amps (roughly about the same as a standard 48 volt e-bike charger produces).

Next, install a charge controller capable of at least 48~60 volts to limit the solar charge. The controller will shut off when the battery is fully charged. MPPT controllers are about 30% more efficient than the old PWM controllers, but are much more expensive, so to keep a low budget, a PWM will do fine..

Here's an example of a reasonably priced 48~60 volt PWM controller. If you haven't already done so, you may wish to study up on building a small solar charging system and shop around for best prices for the components you'll need.

https://wholesaler.alibaba.com/product-detail/Suoer-High-Quality-48V-30A-Solar_60709728116.html?spm=a2700.details.maylikever.10.67991a18tofD08


Renogy has some nice 20 watt mono panels for a decent price. I use their 100 watt mono panels on my Vanagon camper and they work great.

https://www.renogy.com/renogy-20-watt-12-volt-monocrystalline-solar-panel/
 

Scooteretti

Active Member
Here is a video by one of our customers who built himself a trailer with panels. His video will show you what his real life experience was with a solar panel trailer that he built himself for his Pedego City Commuter.

 

Alex M

Active Member
4*20W panels with max theoretical current 1.3A will take 2 days to charge deeply discharged ebike battery. Assuming good weather and no shade.
The biggest issue is carrying/towing a structure like those in videos.

Solar on shore homes works (in certain climates) because you can have A LOT of panels on the roof and it will be harvesting energy all day, as long as the roof isn't shaded.

MPPT is not 30% more efficient, this is old wives tale repeated by sellers without much thinking. It does have certain advantages on big arrays. Temperature affects MPPT output more than with PWM controllers, there can be scenarios when MPPT would harvest less than PWM.