Solar battery charger

I bought a super cheap solar powered shed light from Harbor Freight. It is functional, but that is about all I would say about it.
This is a link to the light.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95573

I know its crap, but I just wanted it for when the power goes out.

The solar panel is a battery charger that comes with 4 AA Ni Cad 500 Mah rechargeables. It has a cable that plugs into the light.

I want to know if it would hurt to put 2500 Mah Energizers into the charger? Would they draw more power and cause damage?

This light only runs about 90 min with a 4 watt florescent. If I am not an idiot, wouldn't it run 5 times longer with the good rechargables?

If you want to give a speech on not buying cheap stuff, save it for someone who cares. I just wanted to see how it would work, and to start getting an idea of how to work with solar panels. Just a cheap experiment.

I will probaly buy a decent sized solar panel soon, but that is not in the budget for another few months.

If the solar charger can keep up with the self discharge of the nimh, and the nimhs can tolerate the abuse that the solar panel is going to give it...

Hey batmanacw - not a bad buy for $20. I'd say that solar panel shown will
only trickle charge 4 AA Nicad or NimH as both chemistries are 1.2volts each.
Absolutely no danger of overcharging. So go ahead and swap em out for fully charged NimH's.
The NimH AA can absorb C/20 charge current forever (I read the spec)
after they are full. ie 2500mah/20 = 125ma charge
Get your multimeter and measure what charge currrent is going into the batteries at noon (brightest sun). If less than 125ma your batteries are safe.

Bet it'll be about 20ma from the picture. Let us know.

Thank you very much for your post. I will check it out and post the results.

If it only charges at 20ma, it sounds like this panel would just keep them charged up, but not fully charge them for many days. Would this be a fair assesment?

I bet the batteries are wired in series, and whatever current the panel puts out is around 6 volts. If that's true, 20ma would take about 125 hours of full and direct sunlight to put 2500ma into the batteries. Add about 50% to make up for charging losses, and you are close to 200 hours. Only count on 3-4 hours of full and direct sunlight in the winter, maybe less areas that experience a lot of cloud cover. It could take months, or more realistically the NiMH batteries will never reach a completely full charge. Of course 80% of 2500mA is still a lot more than the nicads would hold.

But on a more positive note, I think that panel will give you more like 60-80mA. It looks fairly similar in size and construction to a solar motion detector light I had, and that panel put out over 80ma in optimal light to a 6 volt SLA battery.

Either way, you should consider using low discharge AA batteries such as Eneloops or Hybrids.

I charged up my energizers with the 15 min charger they came with and the light ran for about 6 hrs. straight. It was noticeably dimmer when I turned it off at 6 hrs but still decent.

I will finish charging up the original batteries and see how good it does. I haven't had enough sun light to check the output yet. Its been snowy and rainy so not much sun!