Design for solar trickle charge system for stored

[edpsycho]

Hi folks,

I have a pair of Trojan J185P 12V deep cycle lead acid batteries that I use for extended camping trips.

The batteries are not used regularly and are in storage.

Since you're supposed to keep your stored batteries charged. I use a standard 10 amp automobile battery charger, and I try to give each battery a few hours of charge every few weeks, but of course my discipline with regard to doing this is embarassingly inconsistent.

Anyway, I have a 10 watt solar panel. It puts out 13V at 1A in full sun. I figure, why not use this to trickle charge? But my issue is, if you charge the two batteries in parallel at 12V one of the batteries will have a tendency to get "lazy".

My scheme would be to get two of these TPS-545 cheapie charge controllers that are being sold on eBay and wire up the two charge controllers in series. That way I would split the charging current between the two batteries (approx 500ma) and keep them trickle charged.

I've only got 1 10W panel, and don't want to go to the hassle of wiring up a 24V charging system, and it is important to keep expenses to a minimum.

I just wanted to see if anyone could offer comment or insight.

Proposed wiring diagram:
http://mtoal.dyndns.org/images/solar.jpg

cheapo charge controller eBay Seller's store
http://electronics.search.ebay.com/_Gadgets-Other-Electronics_W0QQcatrefZC12QQsacatZ14948QQsassZsudo ku2

cheapo charge controller Specs from manufacturer:
http://china-export-trade.com/solar-charge-controller-C-TPS-545.html

[conundrum]

You might take a look at All Electronics.com or Surplus Center.com for controllers and supplies.
If 12V Man is around I am sure he can add good input on this.

As an aside, I wonder if the auto makers are still using those "disposable' solar panels on new cars to keep the computer alive until they are sold? I have heard that they can often be picked up for next to nothing, although I have to wonder why they would not re-use such a thing?

[justmyluk]

Hook your batteries up in parallel as you described, then hook the solar panel across the batteries as follows: The positive (+) to one battery and the negative (-) to the opposite battery. You should get an even charge across both batteries.