Trikin'

I have a 36V 9.6ah batt, and while touring I'd like to be able to recharge the battery with solar. I've found a site that provides flexible solar panels(siliconesolar.com)my thought is these panels can roll up into a managable size and for touring that's total independence. Any others in here who use solar to recharge your battery(or 2) as well as your cell phone, ipod, MP3 player etc......Your wisdom ('s) are greatly appreciated

prathmann

You're going to need a lot of panels (or many days of charging) to recharge that battery. Their 11" x 13" panel size is speced to put out 15.4V at 200 mA or about 3 W under ideal conditions (sunny warm day). Your battery capacity is about 350 W-hrs. So one of those panels would take at least 350 W-hrs/3W = 120 hrs. to charge the battery even assuming perfect charging efficiency - reality might be more like 160 hrs. And remember that you only get that output while the sun is pretty high in the sky. OTOH, if you wanted to recharge the battery in only about 4 hours then you'd need about 40 of those panels appropriately wired up and controlled.

edcastrovalley

Here's how I charge my ebike with solar. I don't carry solar panels on the bike but I do recharge them from solar. I have a 12 volt dc system with about 8 golf cart type batteries and a solar charge controller located in the garage. I only bought 2 of the batteries, the rest people gave me. I bought the used solar panels off Craigslist from a solar contractor at a good price. Even the wire is used, but I did spend about $15 for each of the solar panel stands on 2x4 lumber and painted them with leftover house paint. With this system I charge (or power) all our cell phones (4 of them), our wireless router 24/7, our porch light and a few other things. All this effort saves about $50 a month on the electric bill so I have pretty much already recouped my investment. Plus I picked up each piece one at a time as I could afford to.

As for my ebike, I was charging the battery with the charger that came with my Amped Bikes kit but, I was plugging it into my inverter which consumed a lot of power. It's a good charger but it's inefficient to convert dc to ac only to have the charger convert back to dc again. I had to wait for a very sunny day to do that. I ended up buying a Hobby King 1010b RC lipo charger which do not use alternating current but are made to charge off your car battery out in the field at 12volts dc. It's perfect with my solar setup and it's fully automatic and will balance batteries, etc. I even bought a couple Turnigy lipo batteries as booster batteries which are made to work with this charger.

edcastrovalley

Forgot photo...

Trikin'

Sadly, turns out this isn't any where feasible (Local Ebike store), not for what I wanted anyways. There doesn't seem to be a trickle charger controller system available. All I wanted was to be as self efficient on the road as I could be, so I stay at a private tent site when needed to recharge no hardship there (showers, laundry)....

edcastrovalley

I see. The word "touring" should be a big hint. Maybe this website will give you some ideas. The guy has a nice Surly Big Dummy cargo bike that he tours on and has a flexible solar panel.

https://bikeforth.org/2010/07/

Mabman

There is some interesting data here: https://solarbike.com.au/solar_module.php

It seems to me though that all the long distance type e biking trips I have read about on the web involve extra batteries and long lunch breaks to top off the charge. A high amp charger would be best for this also.

Here is an example: https://electricbicycle.iblog.co.za/2...a-fascinating/

sunnyday

I have 2 lifepo4 chargers on order...

1 is a 110 volt / 3 A/h charger

the other is a

110 volt / 6 A/h charger...

when they arrive, I will be hooking them up to a wattmeter then to my 110 volt outlet. This will tell me exactly how much watts/amps each of these chargers pull when charging my
lifepo4 -48 volt /20 A/h battery

with that info , im thinking it may be feasable to build a rear trailer which could haul a single 100 - 190 watt - 12 volt solar panel , which is then hooked to a inverter in which the charger can be plugged directly into and charge the battery pack as it is being used.

I know where I can get a 190 watt panel for $329 ..here the stats on it

Max Power: 190W

Open Circuit Voltage (Voc): 21.6V

Short Circuit Current (Isc): 12.1A

Maximum Power Voltage (Vmp): 17.2V

Maximum Power Current (Imp): 11.04A

Weight: 40 pounds

Dimensions (inches): 61 3/4" x 37 1/2" x 1 5/8


On a sunny day, this panel should have no problem putting out a constant 10 + amps..

the panel weighs 40 lbs..but that could be reduced a bit by taking the frame off the panel.

The key to all of this is finding out exactly how many watts/amps is drawn by each individuals charger.....and that will vary based upon if you have a charger that charges at a 2 A/H rating or 8 A/H rating ,etc...

I will be testing a 3 A/h and 6 A/H charger.

sunnyday

its ashame that solar flexible laminate panels are still quite expensive...THAT WOULD BE THE easiest and lightest way to go....

prathmann

I'd be cautious about removing the frame from the panel. Such panels can be rather fragile and should be properly supported if transported on a trailer. And you'll want an adjustable support so the panel can be oriented to face the sun.

Sounds like you're planning on taking the DC output of the panel, converting it to AC with an inverter, and then using a charger that turns it back to DC. Should work, but you're losing some efficiency at each step compared to using the DC from the panel to directly charge the battery pack.

sunnyday

Yeah, I know about the loss of effiecencys going from dc/ to ac/ back to d/c...

but I dont think I can take 3 or 4 , 12 volt panels and wire them so they would charge the lifepo4 battery directly....I think the lifepo4 battery needs a special charger , and using direct d/c volts from a solar panel may not be suitable for lifepo4...

now if it was just lead acid batterys..then its no problem...

the lifepo4 is 48 volt... but it needs at least 58.4 volts D/C/ input to charge it fully...

most 12 volt solar panels put out a max around 21.4 volts open circuit in full sunlight and about 18 volts under load...this means it is possible to genrate enough voltage from 3 solar panels wired in series...which should put out a 54 + volts on a average spring/summer day....so that would be a workable setup..BUT..you still have the problem that the lifepo4 battery may not like being charged up directly from solar d/c panels...

sunnyday

heres a typical 80 watt / 12 volt panel off ebay :

Power at STC ( pm ): 80 Watt

Maximum Power voltage ( Vpm ): 17.9 Volts

Maximum power cusrrent ( Ipm ): 4.84 Amp

Open circuit voltage ( Voc ): 21.9 Volts

Short circuit current ( Isc ): 5.17 Amp


under load, you can expect about 18 volts and 5 amps....wire 3 of these in series and you have 54 volts which would not charge the lifepo4 fully, but should be a very nice supplemental charge to ensure the lifepo4 doesnt go completely dead while cycling...

so this is 5 amps for a 80 watt panel....

you could go with a 50 watt / 12 volt panel , wire them in series for about 54 volts ...and have 3 amps of chargin capacbilitys...but once again, I do not think it would be wise to just wire the solar panels directly to the lifepo4 battery to charge it, becasue lifepo4 batterys probably require some type of special charging circuitry to safely charge the lifepo4 battery...just like nimh, nicd, lipos ,etc need a special charger...

If they could make lead aicd batterys as light as lifepo4 , then it would not be a problem to directly charge the batterys right off the solar panels

sunnyday

does anyone know where we could find out if it is possible to safely charge lifepo4 batterys by using the d/c from solar panels ?

or do lifepo4 chemistry require a special charger ?

if not , then the 3 solar panels wired in series should work in keeping the lifepo4 battery charged to a useable state. Since the 3 / 12 volt solar panels wired in series would be putting out about 52- 58 volts , then there would never be a worry of overcharging the lifepo4 battery { if using a 48 volt lifepo4** ....so that would be a big advantage....you would not need to monitor the charging , since it would be impossible for 52-58 volts to overcharge the 48 volt lifepo4....

sunnyday

if the above scenario of just using solar panels connected directly to the lifepo4 battery would not properly charge the lifepo4 because it needs a special charger...then the other alternative is the one I stated initially...

using 1 larger 12 volt panel of 100 - 200 watts and hooking that to a inverter , then using the inverter to power the special lifepo4 charger , and then hooking the charger to the lifepo4 battery while cycling.

this may be the only feasable way to use solar to constantly recharge the lifepo4 battery while cycling.

sunnyday

if either of those 2 scenarios would work, I think one would still have no other alternative but to haul the solar panels on a pull behind trailer...unless someone can think of some way to safely mount the panels to the bike, so they would collect adequate sunlight, but not create terrible resistance and block the cyclists vision.

edcastrovalley

If you have a lifepo4 battery with a bms you should be able to charge directly from several panels wired in series and have the bms monitor the charging just the same as it would for any other charger. I would carefully monitor the voltage with a volt meter for at least the first couple of times though. I would check the voltage of each cell too.

sunnyday

Im not sure....isnt the BMS just a monitoring system of each lifepo4 cell to ensure it isnt overcharged ? I dont think the BMS is involved in the proper chemistry system to charge the lifepo4, in the way a correct lifepo4 charger would do......all the BMS does is ensure no cells are overcharged...it doesnt provide the proper chemistry or electronics to ensure the lifepo4 is charged with the proper charging system.

then again..maybe im wrong ?

edcastrovalley

I was looking into doing this back in October and at least one guy said it works. See the post here...

https://www.bikeforums.net/showthread...=#post11643423

Sangesf

Ok, I was going to leave this thread alone, but I need to interject something now.. There is no real easy way to recharge batteries as you're riding with solar panels on.
They are just fragile enough to "break" while riding unless you have some serious know-how on shock absorbency...
The setup that I use/have used is external to the bike.. The panels need to be large enough to have an effect in charging the batteries.
The size required for such a feat would be counter productive to using them while riding even if you could help with the shock... They would weigh too much and not provide anywhere close to the current used while riding.

sunnyday

Maybe true, but you were only using the lowest grade solar panels..correct ? Harbor freight panels really are the cheapest of the cheap.....

As soon as my chargers come in, I will be able to put a wattmeter on them, and see exactly how much power the chargers must have to charge the lifepo4 pack.

crackerdog

Check out Endless sphere for some great info about electric bikes and especially about BMS. There is a group there that designed a BMS and shared all the info on that site. You will understand how a BMS works after reading all that.
If you 'transform' DC to AC and back to DC, you will lose so much power that you will need a trailer twice the size.

Sangesf

For the price of the expensive solar panels, you might as well just buy a larger battery.
The range to weight ratio is much better with battery then solar.
Easiest thing is like what I did.
Two motors, two light large batteries, regen and your good to go.
I'm pretty sure, if I can get 2 - 36v 30AH 30C Lipo and kept my speed at 17mph I could easily achieve 200m distance if I pedaled a little on the starts.

edcastrovalley

[QUOTE=Sangesf;12079022
Two motors, two light large batteries, regen and your good to go.
I'm pretty sure, if I can get 2 - 36v 30AH 30C Lipo and kept my speed at 17mph I could easily achieve 200m distance if I pedaled a little on the starts.[/QUOTE]
That's not much more than 10 watt-hours/mile for 200 miles. You must live near some pretty flat terrain with some nice roads.

Sangesf

South Florida.. All flat. Also, a 30C Lipo battery usually gets a little more of the AH rating when you only run it at 1c. So I figure with the 30C's I would get probably 33ah which is about 12w per mile. Which is entirely feasible if you have a lighter bike. (my bike is pretty heavy, because I have ALOT of extra chit on it.