On Feb 23, 9:57 am, "Quint" wrote:
. . . Any ideas on size, whether I need
a controller and how to connect it (plug into the cigar lighter with
the switch on both or something more permanent)? Your experiences
would be helpful. Thx

1% of battery capacity in amps is about right for floating, so 2x105a
batteries would be about 2 amps or a 24 watt panel. Bigger, you risk
gassing electrolyte off in the summer; too small, and there's not
enough oomph to keep things topped off in winter. Pluggin' into the
cigar lighter is fine with just a 2 amp load, but the receptacle
should be fused, they usually are fused at 20 amps or so. Directly
connecting to the batteries without a fuse is a no-no, fire hazard.

One thing to watch out for is: disconnecting (switch "off") the
batteries while the panel is plugged in, as the panel can drive your
DC circuitry up to 18 volts or so with just a tiny load present, like
status lights, radio memories, etc., and blow them out.

I've been running 40 watts of panels on 500ah of batteries, and it's
amazing, all the cell's S.G. have stabilized at 1.275 after a few
months of 5ah or less of load each day. Before, I was intermittantly
charging the batteries and the S.G. range when fully charged varied +-
0.010 after a few months, requiring an equalization charge.

I think a float panel on a boat that's intermittantly used is really
kind to the batteries.