Can e-bike batteries be charged with solar panels?

[SOLARebike]

how is this one?

Solar MPPT Boost Converter

300 Watt Boost MPPT for Solar Charging 36-72V Ebike Batteries. 2021 UPDATE: Product Discontinued, manufacturer no longer availalbe

www.ebikes.ca

I paid $350 for my first Genasun boost controller in 2015 because I needed to order a custom voltage but their prices have come down and their offering has expanded so it's more like US$205 for their fully potted "WP" waterproof model.

The Chinese model imported by Grin Tech was tested by Justin on his 2018 SunTrip from France to Iran and appears to be popular with solar bike enthusiasts who don't have the budget for the Genasun. The Chinese one is 50% heavier, is slower to adjust to changes in insolation (riding under trees, for example) and is not waterproof but otherwise appears to be quite adequate.

I've also heard that it can't handle more than about 200 watts but the GenaSun's 350 watt rating is also misleading. Given the 8A maximum PV input, you would need a 44V panel (350/8) which you will not find and even if you did it couldn't charge a 36V nominal 10s battery pack because the input voltage MUST be lower than the battery's lowest voltage.

Alex Hofvander did an in-depth review based on his experience with both:

 

[Handlebars]

Thank you. I'm glad I asked you.

Given the 8A maximum PV input, you would need a 44V panel (350/8) which you will not find and even if you did it couldn't charge a 36V nominal 10s battery pack because the input voltage MUST be lower than the battery's lowest voltage.

I haven't got a good understanding of what that means, but it doesn't sound good for what I've bought

I have a Renogy 100W panel to start with, and that MPPT, but I haven't tried them yet.
Grin said I just need to plug it into the 48V battery. But now I'm not so sure.

Thank you for anything more you can tell me!

 

[SOLARebike]

I haven't got a good understanding of what that means, but it doesn't sound good for what I've bought

I have a Renogy 100W panel to start with, and that MPPT, but I haven't tried them yet.
Grin said I just need to plug it into the 48V battery. But now I'm not so sure.

I didn't mean to alarm you. I was just saying that the Genasun controller's 350 watt maximum power input rating is unachievable because no one makes an 8 amp, 44 volt solar panel.

The business about the 44V theoretical panel not being compatible with a 36V ebike battery doesn't apply to you since you don't have a 36V battery (I do). Most solar charge controllers on the market today are "buck" or "step down" types meaning they convert higher DC voltage to lower DC voltage. This makes sense when charging 12V or 24V lead acid batteries from a bunch of solar panels connected in series because the charge controller's input voltage is going to be higher than the battery's voltage.

The Genasun and your controller are "boost" or "step up" types meaning they convert lower DC voltage to higher DC voltage. This is much less common but it's exactly what you want for charging a relatively high voltage ebike battery (36V, 48V, 52V or even 72V) from one or two solar panels which will typically have lower voltage than the battery. My point was that having lower input voltage than output voltage on the boost charge controller is not optional.

If your 100W Renogy panel is like most 100W panels, it probably has an open circuit voltage (Voc) around 22V and a maximum power point voltage (Vmp) around 18-19V which is just perfect for your 48V battery. Assuming your battery is lithium ion and not LiFePO4 or LiPo then it's made up of 13 cells in series (13s) and is around 3.2V*13 or 41.6V when empty and 4.2*13 or 54.6V when full. Your charge controller needs to be set for 54.6V or slightly less.

The Grin product page says "When using with Li-Ion batteries, it is recommended to set a custom voltage as a charge termination" so unless they've told you otherwise, you'll need to set this yourself? Read the manual. If it's like other boost controllers, it's powered from the PV (solar) side so to power it on and check the settings, connect the solar panel first and only connect the battery once you've confirmed the correct output voltage setting.

 

[Handlebars]

I didn't mean to alarm you. I was just saying that the Genasun controller's 350 watt maximum power input rating is unachievable because no one makes an 8 amp, 44 volt solar panel.

The business about the 44V theoretical panel not being compatible with a 36V ebike battery doesn't apply to you since you don't have a 36V battery (I do). Most solar charge controllers on the market today are "buck" or "step down" types meaning they convert higher DC voltage to lower DC voltage. This makes sense when charging 12V or 24V lead acid batteries from a bunch of solar panels connected in series because the charge controller's input voltage is going to be higher than the battery's voltage.

The Genasun and your controller are "boost" or "step up" types meaning they convert lower DC voltage to higher DC voltage. This is much less common but it's exactly what you want for charging a relatively high voltage ebike battery (36V, 48V, 52V or even 72V) from one or two solar panels which will typically have lower voltage than the battery. My point was that having lower input voltage than output voltage on the boost charge controller is not optional.

If your 100W Renogy panel is like most 100W panels, it have an open circuit voltage (Voc) around 22V and a maximum power point voltage (Vmp) around 18-19V which is just perfect for your 48V battery. Assuming your battery is lithium ion and not LiFePO4 or LiPo then it's made up of 13 cells in series (13s) and is around 3.2V*13 or 41.6V when empty and 4.2*13 or 54.6V when full. Your charge controller needs to be set for 54.6V or slightly less. Presumably, Grin has already done this for you if they say it's ready to use with a 48V battery pack.

Beautiful explanation, SOLARebike. Many thanks for your help.

 

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Upon closer investigation, PowerButler looks like they weren't shipping outside Europe and the dead YouTube channel with the unanswered comments looks like they're not in business any more. I've deleted the post to avoid wasting anyone's time with them.

Yes, i didn't bother taking a chance on them!

The first two are just lazy typos while the -5% power tolerance is incomplete but not surprising. PV modules are commonly rated with power tolerances with -5w/+5w (US, a few

How is the "Operating Temperature: 40-80 degrees" a typo, none of those numbers make any sense to me.

I'm more offended by the price. $900 for 205 watts? That's $4.39/watt! Unless these Rambos are adding value to what they're selling, you can and should get the same quality from the usual scumbags (AliExpress, Alibaba, eBay, Amazon) for $1 to $2 per watt. Given the lack of attention to detail in spelling out the product specs, I wouldn't hold my breath.

I'm ok for panels for a while with how i wish to use them: Ride for a day or so with agility on 2 wheels (no roof or trailer), then camp and charge for a day or so, vice versa.
As i mortgaged the house & paid a fortune for 2 of these: https://p3solar.com/portfolio/p3-125/ and one of these: https://www.suntactics.com/scharger5-portable-solar-charger
I can get about 114W out of each of the P3-125's on a good Aussie sunny day and check out the size and weight.

 

[SOLARebike]

How is the "Operating Temperature: 40-80 degrees" a typo, none of those numbers make any sense to me.

Have you looked at the specs on your P3-125?

And what's up with that -15% tolerance rating? Ouch.

I'm ok for panels for a while with how i wish to use them: Ride for a day or so with agility on 2 wheels (no roof or trailer), then camp and charge for a day or so, vice versa.
As i mortgaged the house & paid a fortune for 2 of these: https://p3solar.com/portfolio/p3-125/ and one of these: https://www.suntactics.com/scharger5-portable-solar-charger
I can get about 114W out of each of the P3-125's on a good Aussie sunny day and check out the size and weight.

The P3 product looks like it uses thin film PV made by PowerFilm. I took a long, hard look at that technology when I was first getting started with solar charging ebikes back in 2008. The power to weight ratio is excellent but the power per square meter is terrible, less than half of what you get with modern Sunpower cells. I don't find the prospect of 2 hours of stationary charging for every 1 hour of riding appealing on a bike tour so I wouldn't be interested even at half of their current price but clearly there are use cases where such limitations are not a problem.

The Suntactics charger is the same weight and size as dozens of identical solar USB chargers on the market today but the US$20/watt price tag needs to come down to US$2-3/watt to stay competitive.

What frustrates me is that the Sunpower cells only weigh 6.5 grams each so it's possible to make stiff, strong encapsulations weighing less than 1 kg (2.2 lbs) per 100 watts. Companies like SunCat, Gochermann, LightLeaf, Mito and Wattlab make such custom panels in small quantities for solar race cars and race boats for US$10-20/watt. Surely, there's a market for solar panels that are somewhere halfway between today's cheap/overweight Sunpower folding panels and these expensive ultralight products in both weight and price.

 

[webcurl]

Have you looked at the specs on your P3-125?

View attachment 62261

And what's up with that -15% tolerance rating? Ouch.



The P3 product looks like it uses thin film PV made by PowerFilm. I took a long, hard look at that technology when I was first getting started with solar charging ebikes back in 2008. The power to weight ratio is excellent but the power per square meter is terrible, less than half of what you get with modern Sunpower cells. I don't find the prospect of 2 hours of stationary charging for every 1 hour of riding appealing on a bike tour so I wouldn't be interested even at half of their current price but clearly there are use cases where such limitations are not a problem.

The Suntactics charger is the same weight and size as dozens of identical solar USB chargers on the market today but the US$20/watt price tag needs to come down to US$2-3/watt to stay competitive.

What frustrates me is that the Sunpower cells only weigh 6.5 grams each so it's possible to make stiff, strong encapsulations weighing less than 1 kg (2.2 lbs) per 100 watts. Companies like SunCat, Gochermann, LightLeaf, Mito and Wattlab make such custom panels in small quantities for solar race cars and race boats for US$10-20/watt. Surely, there's a market for solar panels that are somewhere halfway between today's cheap/overweight Sunpower folding panels and these expensive ultralight products in both weight and price.

Ah, ok, thanks, my mistake with the operating temps. It's so confusing when most of the world uses metric and this spec sheet throws in inches with degrees celcius but doesn't mention Celcius!
The P3Solar panels are CIGS (Copper Indium Gallium Selenide cells) the Powerfilm's are aSi (Amorphous Silicon cells).

Thin-Film Solar Panels: What You Need To Know

Learn about the different types of thin-film solar panels and how they differentiate on materials, cost, performance, and more.

www.energysage.com

 

[SOLARebike]

The P3Solar panels are CIGS (Copper Indium Gallium Selenide cells) the Powerfilm's are aSi (Amorphous Silicon cells).

I think I might be coming back around to these floppy solar blankets. I've been brainstorming ideas for a fabric tail fairing to improve aerodynamics and the low weight and flexibility might offer a way to sew some solar cells onto the fabric. In that scenario, the lower efficiency wouldn't be a deal breaker for me.

Did you pick the P3 product over PowerFilm for a specific performance reason? Or was it something else like price or availability?

I'm also curious about how you use the P3 folder. Do you try to prop it up to catch the sun early and late in the day or do you just lay it out on the ground and take the performance hit? How far do you typically travel in a day? Do you set up camp and stay in one spot for several days?

I think solar ebike charging is an underserved and undiscovered niche market and I'm trying to understand it better. Not everyone is going to want to do 80-100 miles (130-160 km) per day like me.

 

[webcurl]

Did you pick the P3 product over PowerFilm for a specific performance reason? Or was it something else like price or availability?

I'm also curious about how you use the P3 folder. Do you try to prop it up to catch the sun early and late in the day or do you just lay it out on the ground and take the performance hit? How far do you typically travel in a day? Do you set up camp and stay in one spot for several days?

I think solar ebike charging is an underserved and undiscovered niche market and I'm trying to understand it better. Not everyone is going to want to do 80-100 miles (130-160 km) per day like me.

I picked the P3-125 as the highest output i could get for the folded size & weight. Each one fits into one of these nicely on the front: https://www.ortlieb.com/gravel-pack
Powerfilms were larger when folded & heavier. Also assumed CIGS would be more efficient. I definitely didn't pick it based on price
I deploy 1 or 2 of them at a long rest/break.
I ride for a day, more or less, charge overnight at a power point or camp for a few nights charging during the day, re-positioning every 2, 3 or more hours then repeat.
One of my panels is brown/green the other more green. The browner one works better in full sun, the greener one works better in low light. I have an ultralight parallel & serial cable setup i made with XT60's which i switch depending on conditions.
Hooked up to a Victron SmartSolar MPPT 75/15 with a home made 33Wh LiFePO4 buffer battery (4 x A123 26650's, 13.2VDC, weighs 400g).

 

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Working on a 128Wh Pouch Cell buffer battery (LiFePO4) so that i've got more juice at night to power a notebook (if i take it) & water heater in the morning/whenever (if i take it, modified https://www.aliexpress.com/item/32951896539.html), also more headroom when charging ebike.
I've settled on 12V stuff as it's flexible. I have a modified motorcycle 2 x USB charger (2.4A) and ultralight cigarette lighter socket(s) with a cig lighter usb charger that can do USB-C PD (30W).
To charge notebook, motion sensing alarm, phone, Garmin Vario Radar & Garmin InReach Mini, etc.

 

[webcurl]

Also have one of these with XT60's: https://www.aliexpress.com/item/32788051087.html
For if any of the Victron/Buffer battery/cables setup fails i can still charge phones, etc. but not ebike. Weighs about 150g.

 

[SOLARebike]

Hooked up to a Victron SmartSolar MPPT 75/15 with a home made 33Wh LiFePO4 buffer battery (4 x A123 26650's, 13.2VDC, weighs 400g).

So 500g Victron, 400g 12V battery and then? 500g AC inverter? and 800g AC ebike battery charger? Have you considered replacing all that with the US$30 400g Chinese boost controller and charging your ebike battery directly? You would lose 1 or 2 kg and eliminate the AC conversion losses, both of which would increase your range.

You could run your 12V accessories directly from the ebike battery using a small buck converter. I use this one for lights, horn, alarm and USB chargers.

I tested immersion water heaters and was disappointed to learn that heating 2 cups of water to boiling cost me 3.6 miles (5.8 km) of range.

 

[webcurl]

So 500g Victron, 400g 12V battery and then? 500g AC inverter? and 800g AC ebike battery charger? Have you considered replacing all that with the US$30 400g Chinese boost controller and charging your ebike battery directly? You would lose 1 or 2 kg and eliminate the AC conversion losses, both of which would increase your range.

I would like to do this but i'm working with a Bosch ebike
I would still need the Bosch charger for when charging at a mains power point or some other switch mode supply.

 

[SOLARebike]

I would like to do this but i'm working with a Bosch ebike
I would still need the Bosch charger for when charging at a mains power point or some other switch mode supply.

Well, that does complicate things a bit. For starters, cut off the Bosch plug going into the battery from the charger and splice in a good 3 pin XLR connector or MT30/MT60 (since you're already familiar with XT60s) or even Andersons, whatever you might have on hand. That way, you can still use the stock charger at home and you can connect their proprietary plug to whatever you want.

I've ordered one of those Chinese boost controllers just to play with it but it hasn't arrived yet. You might be able to tap into a 5V source inside that or use a 5V regulator to step down the output voltage to the third Bosch pin. If it doesn't work, you still have your original set up. For someone who has built their own battery pack, this should be a piece of cake, no? See the Grin Tech comment on this video for confirmation of this setup from a trusted source.

For charging from mains, I got this tiny, light, cheap one for emergencies only. It's only 2A but I would only use it for overnight charging if I hit an extended rainy spell. Same setup as above for the third pin. I wouldn't want it for regular use but for occasional use under close supervision the size and lack of fan meet my needs.

 

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As i said before: "There seems to be a distinct lack of reliable information worldwide on this "+5VDC on CAN bus line trick", the discontinued 12V Bosch Travel charger & powerbutler.de in regards to newer Bosch batteries & Y-Cables (dual battery setup)"
There is some old info on these forums: https://www.pedelecforum.de/forum/i...sch-ladegerät-akku-ladeverhalten.12896/page-6
but my German is not the best & translations are not the best for technical stuff.

My system has just come out of warranty and i will soon start experimenting.
If it works then i will still stick to the Victron & buffer battery to keep a generic 12VDC system and a stable system for step-up conversion. The Victron also provides PV input & load out stats via Bluetooth.
And maybe a lightweight 19VDC power supply for mains connection to simulate PV, that way i can charge the bike, my buffer battery and all other devices simultaneously.
I have one of these already for the 5V: https://www.aliexpress.com/item/32880983608.html (which will be connected to the 12V side as it has a 24VDC input limit) & one of these on order: https://www.aliexpress.com/item/4000232811203.html
I already have a spare Bosch plug.

 

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And if i get completely sick of Bosch (as i've already spent a small fortune) then i'll get this: https://wattwagons.com/products/ultimate_commuter_pro and have far less problems solar charging!

 

[webcurl]

See the Grin Tech comment on this video for confirmation of this setup from a trusted source.

This information comes from testing with older batteries i believe. The comment may only be a year old but the information is older.

 

[SOLARebike]

As i said before: "There seems to be a distinct lack of reliable information worldwide on this "+5VDC on CAN bus line trick", the discontinued 12V Bosch Travel charger & powerbutler.de in regards to newer Bosch batteries & Y-Cables (dual battery setup)"
There is some old info on these forums: https://www.pedelecforum.de/forum/index.php?threads/classic-bosch-ladegerät-akku-ladeverhalten.12896/page-6
but my German is not the best & translations are not the best for technical stuff.

It sounds like you're ready to "be the change you want to see in the world." You've done the research, you've ordered the parts, now do the tests and report back so everyone can benefit.

That Pedelec forum post is a good resource. Thanks for that. I feel like I understood 98% with machine translation, filling in the gaps with what I already know about how this stuff works. It sounds like the Bosch charger is just a dumb CC/CV device with 5V output on the third pin as a safety lock-out mechanism to avoid exposing the user to battery voltage and to avoid accidental shorts. I'm not seeing anything about any CAN bus communication? Did you read that somewhere else?

Just guessing from the wide range of backwards compatibility on the official Bosch charger product page, I wouldn't expect them to make changes which would block this simple hack because it would make their older chargers incompatible with their newer batteries.

I never cared for the term "pedelec." It sounds like some kind of sex offender involving a bicycle and... perhaps frottage?

 

[webcurl]

It sounds like the Bosch charger is just a dumb CC/CV device with 5V output on the third pin as a safety lock-out mechanism to avoid exposing the user to battery voltage and to avoid accidental shorts. I'm not seeing anything about any CAN bus communication? Did you read that somewhere else?

No CAN communication as such but maybe sequencing, ACK timing, whatever of the 5V on that line. I say CAN bus line as the battery normally communicates state of charge, total charge cycles & detected temperature low & high readings to the motor on that line.

Just guessing from the wide range of backwards compatibility on the official Bosch charger product page, I wouldn't expect them to make changes which would block this simple hack because it would make their older chargers incompatible with their newer batteries.

I spent a lot of money on a discontinued Bosch Travel charger (12VDC input, 2A output) and it won't charge my batteries out of the bike at all but will charge (only 1/2) batteries whilst in the bike. The Y-cable is doing something here.
I use this (whilst swapping batteries around in-bike) when sun conditions are low as to avoid DC-DC-AC-DC conversion and do DC-DC-DC instead
1) Solar PV (31VDC MPP) --> LiFePO4 buffer (13.2-14.4VDC) --> Inverter (~12VDC-240AC) --> Bosch charger (240AC-~42VDC, 2A)
2) Solar PV (31VDC MPP) --> LiFePO4 buffer (13.2-14.4VDC) --> Bosch Travel Charger (~12VDC-~42VDC, 2A)

 

[SOLARebike]

I spent a lot of money on a discontinued Bosch Travel charger (12VDC input, 2A output) and it won't charge my batteries out of the bike at all but will charge (only 1/2) batteries whilst in the bike. The Y-cable is doing something here.

I'm sorry. That sounds really frustrating.

Hey, if you decide you want a smaller 5V regulator that you can fit in a tight spot (like under some heat shrink right next to the connector?) check out the Diodes Incorporated ZXTR2105FQ (PDF). 7-60V DC input, 5V DC output, SOT23 package (2.9mm x 1.3mm x 1mm). You just need to add a couple of capacitors as shown in the datasheet. I'm in the US so I order components like these through Mouser or Digikey but you probably have a local source.

I didn't realize how good I had it with my Grin Tech LiGo batteries.

• They're 98 Wh each so I can take them on an airplane.
• I have massive redundancy with 6 independent batteries wired in parallel. If one cell or a single BMS component fails, the other 5 packs will be unaffected.
• They charge and discharge through the same two wires so I just connect my solar charge controller which is now also directly connected to the motor controller. Solar power goes straight to the motor controller or to the battery, depending on the current load. This reduces battery charge cycles and avoids round-trip losses (~10%) through the battery.
• No battery swapping to keep track of and peak loads are spread across all of my cells instead of 1 of 2 separate batteries.
• I can add or subtract capacity in 98 Wh increments on and as-needed basis.
• If my charge controller fails in a remote area, I can wire my solar panels in series to give me 44 Vmp, connect directly to the battery and let the BMS disconnect at 42V via high voltage cut-off. (This is definitely "plan B.")
• I can program them via an Android bluetooth app to cut off charging at a lower voltage if I want to extend the life of the battery without needing to use a charger that is programmed for lower voltage (I'm a beta tester, I don't think this feature has been released to the public yet).
• The BMS balances the cells without needing to have the pack reach the full 42 volts
• They're fully potted and waterproof (but also non-serviceable)
• I can wire three of the batteries in series to give me a nominal 108 VDC which will run many 110 VAC devices, including my laptop charger and 110 VAC immersion heater without an AC inverter.

Not a paid endorsement. I'm just a fan.