Charging a battery with a solar panel?

Question

I have a boat with an automatic bilge pump, and I want to hook up my battery ( 12 volt deep cycle marine) to a solar panel so that it maintains its charge when the bilge pump kicks on, the bilge pump will only kick on when it rains. I want to know what minimum specs the solar panel should have to maintain my batteries charge. The bilge pump will likely only run for an hour or two a week at most. Thanks in advance for the help.

Answer 1

Hi Conrad

Assuming your bilge pump draws about 2.6 amps, I'd suggest using a solar panel with an output of 5 to 5.5 watts. (They're on sale here in Canada a few times a year for about $50)

These provide 0.3 amps/hour which will easily maintain your battery charge and will not require a charger limiter.

Hope this helps.

Answer 2

You also want to have overcharge protection on the battery in case of constant full sun. What this will do is sense when there is enough charge and shut down the panel, while turning the panel back on when charge is needed.

Answer 3

Take the battery/ charge system specs to those who will sell you a solar panel and they will give you a number of choices. All the wiring info comes with the unit. If you have a good deep charged and fairly fresh battery you probably won't need a solar panel unless the boat is left to sit too long and not used, but where is the fun in that? Your motor will top off your charge if you have a starter/ charging system or if not, just keep a spare battery charged and replacable when the boat isn't used and the rains seem to be unending. That is probably cheaper.

Answer 4

Conrad, if this were me looking, I would want a panel with a 12 volt, 2amp/hour output.

You may be able to get by with less, depending on how much sunshine you get where you are, and how much your bilge pump draws.

Regards,

Dan