Builidng a Solar charger (help appreciated)

 Hi All,

I've had a 75 watt solar panel for years. Right now, it's powering some
fans in my office to keep it cool during the summer. I've hooked up a
12v voltage regulator and some very large capacitors to it (for the
occasional cloud), so I'm not afraid of tinkering with soldering and
low voltage electronics. I want to repurpose the panel to help supply a
small amount of power (12V, 50W+/-) after the next major natural
disaster by charging a battery during the day for lights/radio at
night.

My questions are these:

1. What sort of batteries can I use that can survive cold storage with
no charge for years and still be ready to charge when the need arises?

2. I don't suppose it's as straightforward as just connecting the two
leads from the panel to the terminals on the battery. Are there any "do
it yourself" schematics for building chargers. I'm really looking for
something that will stop charging when the battery is full.

I prefer to build my own, but I also haven't found anything like this
on the market. The solutions I've seen either supply the panel or the
batteries or both. I'm looking to leverage the $400 investment on the
panel that I already have.

  The state of the art in solar charge controller have 'Maximum Power
Point Tracking'. All Solar charger companies feature this on their top
of the line charge controllers. Many solar sites have good background
info on the technique. Price and size varies, but a good inexpensive
mppt controller comes from Solar Converters in Canada.

 A C-12 will pulse charge the batteries very well and has a 12 volt
distribution panel built in. You can also set it for nite lite
operation if desired. I use one with my 90 watts with good results. If
you google for mppt, you'll eventually come across some circuits for
charge controllers. I think there's a Yahoo group about it. Some French
guy came up with one and there's a bunch of people that swear by them.
Pretty low power applications tho.

Max
http://www.northernmichigansolar.com
(major updates 6-24-06)

 Sorry to get off topic here, but I saw this info about power factors
on a link in this thread.

From this page http://70.103.140.128/~northet0/generator.htm

"POWER FACTORS AND HOW TO USE THEM!

I'll make it real simple. My old generator had maximum output of 1000
watts. Maximum long term load rating was 850 watts.

My battery charger was a 10 amp charger. Take the 10 amps, multiply
the output voltage of it, 17 volts and you have 170 watts. The power
factor of the unit was .2, so you take that 170 watts, divide it by
the .2 and you have 850 watts. Add in the 40 watts I was also using in
the cabin and bingo bango, I was using 890 watts of an available 850.
The generator surged wildly, setting fire to a surge strip, burning
out the charger and in the process burned itself out.

Learn about power factors, folks!"



WOW!!!!

I have never heard of a 10 amp, 12 volt charger that requires 850
watts to run it.

Any comments out there?




wrote:

 Fred F. wrote:

The wattage mentioned is that of the output of the charger.
From the sound of the article I would not have a great deal of faith in the
writers tech experience.
I would doubt that overloading the output of the charger would have been the
only cause of the failure mentioned.
It doesnt take into account the losses in the charger and using a power
strip can cause heating problems within it if used unwisely.

Cheers ......... Rheilly P

Where theres a will, I want to be in it.