NiMH solar battery charger

Archiver

I have a 10 watt solar panel that I want to turn into a battery
charger for when I go camping. It is rated at 16.5 volts @ 0.62
Amps. My goal is to charge up to 8 AA batteries (in groups of 2 if
possible). I don't know much about charging NiMH batteries, I don't
want to overcharge (and ruin) them. Is it possible to use a BS2 and
make a NiMH battery charger? If so what will I need to do this? Any
ideas or susgestions will be greatly appriciated.

Thanks,
Tim

Archiver

hiya

I have done a couple of projects that needed NIMH AA batteries and used a Max
713 chip
to charge them via a solar panel. They were stamp projects but the stamp
isnt required
to run the charger. Even better, if you have enough power, the chip can run
your project and power the project.

hope this helps

jeff

In a message dated 4/1/2004 3:49:34 PM Central Standard Time,
tdale4@h... writes:
I have a 10 watt solar panel that I want to turn into a battery
charger for when I go camping. It is rated at 16.5 volts @ 0.62
Amps. My goal is to charge up to 8 AA batteries (in groups of 2 if
possible). I don't know much about charging NiMH batteries, I don't
want to overcharge (and ruin) them. Is it possible to use a BS2 and
make a NiMH battery charger? If so what will I need to do this? Any
ideas or susgestions will be greatly appriciated.

Thanks,
Tim


[noparse][[/noparse]Non-text portions of this message have been removed]

Archiver

--- In basicstamps@yahoogroups.com, "Tim Dale" <tdale4@h...> wrote:
> I have a 10 watt solar panel that I want to turn into a battery
> charger for when I go camping. It is rated at 16.5 volts @ 0.62
> Amps. My goal is to charge up to 8 AA batteries (in groups of 2 if
> possible). I don't know much about charging NiMH batteries, I don't
> want to overcharge (and ruin) them. Is it possible to use a BS2 and
> make a NiMH battery charger? If so what will I need to do this? Any
> ideas or susgestions will be greatly appriciated.
>
> Thanks,
> Tim

From sites that I have found, you can charge NiMH batteries at C/10
where C is the total charge the battery pack holds in mAh. So if you
had a pack that was 600mAH you charge it at 60mA. Charging time is
roughly 1.5 times the amount, so you would need about 14-15 hours for
a full charge. This is slow enough a rate that it won't create gasses
to ruin the built in recyclers too quickly. It's not the greatest way
to do it (which would be to measure the voltage drop as well as
temperature), but it's the poor man's way.

So, for your panel, you would have a rate of 6200mA. this
unfortunately is pretty high compared to what a AA battery runs. I
believe AA run about 1600mAh, so with an array of 8, you would be
charging at about 50% rate. If you want to go this route, you would
just have to set up a current regulator to output C/10 for a simple
setup.

Here are a couple of sites that might help:

http://www.powerstream.com/NiMH.htm - This one talks about the C/10
method, which may not be possible for you. Don't know though.

http://www.angelfire.com/electronic/hayles/charge1.html - This talks
about a fancy charger that looks for the voltage drop in charge. The
parts come from Australia, so I don't know if you can order them
elsewhere, but there is still a lot of info there. Hope this helps.

David