17v solar panel to 24v ebike

Hi
I am trying to put a 17v solar panel (i just found it in my garage) onto a 24v bike pusher. Is there a cheap way i can use this solar panel to charge 2 12v deep cyle batteries in series? Would i need a voltage regulator or something? Any help would be much appreciated. Thanks.

if it's only 17v, you'd have to find or build a dc-dc converter from the actual loaded output voltage of teh panel (probably 12V or so) to the charging voltage of the pack (probably 28-29V).

It would be easier and more efficient to set up your pack to switch to parallel for charging, and then just hook the panel with a series diode to the paralleled batteries, and charge directly.

Either way, if it is a panel smaller than the top of a pickup truck bed. you're unlikely to get much charge on any given day, and it will likely take several days to charge your pack from any given ride. You'd have to see how many Wh you use in a ride, and how many Wh you can actually draw from the panel, to know for sure how long it will take. (or do the charge and time it).

alright, thanks for your help

How many watts is the panel rated for? I'm guessing its something insignificant, like <10W.

Plus, the 17V is likely the OCV, which means its designed to charge a 12V SLA. It won't charge 2 series 12V batteries whatsoever. You 'could' get a boost converter, but it would need to be insanely efficient, have MPPT, and have a super wide input range to be useful.

If you want solar e-bike charging, get another identical panel. Just be warned, it's probably going to take a few days to weeks to charge a reasonable capacity battery with a small solar setup.

You're going to want something like one of these:
http://genasun.com/gvb.shtml

Although a lipo/rc charger would be another option, I've run those straight off solar panels before, but if you want decent efficiency you'll need to set the minimum input voltage on the charger to be the same as the peak power voltage the panel puts out.

Unless the panel is 45w or larger, it's likely to be a waste of time. My guess is that the panel is small, and intended only for keeping the battery on a boat or RV from draining in the off season.

If so, it's not going to do much more than charge a very very small 12v battery, like one for a yard light.

Harbor freight has some solar panel setups good for charging one 12v battery that go on sale from time to time. Three 15 w panels and a charger in the kit. Two of those kits would have enough capacity to charge both your batteries every day.

you could buy a cheap RC charger and use the solar to directly power the charger and charge your batteries.

The moment you get cloud the charger will reset and stop charging tho.


Might work on the smallest rc charger you can find, something like a 50/70 watt charger and lower the charge amps

That would work, but I think you'd need to buffer the solar panel output with another battery. Even a very small sla would work. Then the RC charger will convert 12v input to 24v output. Likely would take a 6s charger to do that.

Still limited to the output of the panel. For example, a 15w panel would put out about 50-70 watthours per day. So a large battery would take days and days to charge.

Get one of these if you want to save some cash, mine work perfect on a 30 watt panel.

http://www.ebay.com/itm/DC-DC-4-40V-to-1-25-37V-2A-Converter-Step-Down-Buck-Module-red-Voltmeter-280-/160831014336?pt=LH_DefaultDomain_0&hash=item25724685c0#ht_3631wt_1170

Sunsaver also makes a charge controller for 24 volts