Looking for low power panel

asteroids

I have a 12V device that consumes about 0.5w. I'm looking for a decent panel to charge up a 12ah battery. I tried Harbor Freight but that didn't work. Suggestions?

BB.

A 1/2 watt * 24 hours per day = 12 Watt*Hours per day

Based on 3 hours of sun per day (excluding dead of winter):

• 12 WH per day * 1/0.77 panel+controller losses * 1/3 hours of sun per day = 5.2 Watt solar array minimum

So, a 10 Watt array should work very well (even into winter):

Solartech 10 Watt Multicrystalline Solar Module $52

And a small charge controller:

SunGuard 4.5 Amp 12 Volt Solar Charge Controller $30

I would not put a 10 Watt panel on a 12 AH @ 12 volt battery without a charge controller of some sort.

If I was going to size the array based on battery AH Rating:

• 14.4 volts charging * 12 AH * 1/0.77 panel eff * 0.05 rate of charge = 11 Watt minimum
• 14.4 volts charging * 12 AH * 1/0.77 panel eff * 0.10 rate of charge = 22 Watt nominal
• 14.4 volts charging * 12 AH * 1/0.77 panel eff * 0.13 rate of charge = 29 Watts "cost effective" maximum

Note that if the battery colder, it will have lower self discharge (and significantly lower AH capacity if below ~50F).

If the battery is "hot" (95 to 110F or so), it will have higher capacity and higher self discharge (tend towards a bit larger solar panel).

So that gives you a few numbers around which you can pick your solar panel and charge controller.

Of course, I am sure you can find lots of less expensive panels and small charge controllers on Ebay and possibly Craig's List.

-Bill

waynefromnscanada

BB. wrote: »

[*]12 WH per day * 1/0.77 panel+controller losses * 1/3 hours of sun per day = 5.2 volt solar array minimum

Typo I'm sure, but might cause confusion.
Peace

BB.

Wow... Where did that come from????

Thank you Wayne.

-Bill