David Nebenzahl wrote:

Told a guy I'd do some research for him into a small simple solar system
for use in maintaining the charge on a 12 volt automotive battery. Found
this at Harbor Freight:

http://www.harborfreight.com/cpi/cta...emnumber=96418

It's a 12 volt, 15 watt panel for cheap ($70).

I'm thinking that all he needs to do is wire it up to his battery to
trickle-charge it. I think I'd add a diode (IN200x) in series for
protection. So will this work?

Since they don't list the output voltage for the panel, except to say
"12 volts" in the description, I guess one could opt for this larger one:

http://www.harborfreight.com/cpi/cta...emnumber=40085
(20 watt panel, made for charging auto & RV batteries, $190)

which says it maintains a charging voltage of 17.5 volts, which seems a
little high: perhaps a string of 3 or 4 diodes in series would drop the
voltage just enough to bring it down to the recommended 13.6 volts or so.


The 45W three panel package that Harbor Freight sells for ~$200 is the
best value $/W and the panels are decent. You have to replace the junk
charge controller they provide with a decent unit though.