Solar trickle charge sizing....


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portage lakes, oh
So... I have a 25 watt flexible solar panel. I'm hoping to hook it up in a way that I can attach it to the ski/tow bar when i pack up for the day, plug it in, and have it trickle the battery banks while I'm gone. I have 2 banks... one pair of starting batteries, and soon another single/pair of deep cycle for house batteries.

I have the auto-bilge hooked up that bypasses the switch to the batteries, so that's always a concern, but I'm figuring the 25 watt panel should keep things topped up just fine. maybe it's not big enough though? I lost a battery last season due to deep discharge. Didn't get to the boat as much, and lots of rain probably hit the bilge a lot harder, and less charging overall did me in. Trying to stay ahead of things a little better next year...

Any suggestions on charge controllers to keep the batteries from overcharging? I'm guessing I need 2? one for each bank, and then parallel the batteries in each bank?