Small Solar Panel Outlet
Do I need a new battery for my solar setup?
I acquired a deep cycle 115AH battery from my dad’s boat that im using for a small solar power system with an inverter. The battery is about 5 or 6 years old and has barley been used, but it has been sitting most of the time, not charging. When I charge it with a car battery charger (powered fro the AC outlet), it charges to 13.2v max (too low?) and only holds it above 12v for about 2 days. The panel I use to charge it puts out 15w at 1.2 amps, do you think that’s way to small of a solar panel to charge the battery effectively or is the battery bad?
Hey Brandon, Mike is probably right, but it’s possible the charger you are using, the AC powered one, is not raising the battery voltage adequately either. As long as you have this stuff, here’s what I would do. Charge it up with the AC charger one more time, then unhook it and hook the panel up, then leave the panel in the sun for several days, checking the voltage once in a while. It should eventually get up past 14 during charging, then stay above 12.6 all night after a few days of sun. Don’t worry about overcharging the battery, with that little panel, it won’t be a problem. There is a rule of thumb on lead acid batteries that if the charging source amperage, in your case 1.2 amps, is less than 2% of the battery amp hour capacity, you do not need a charge controller, so let that panel run as long as you can stand it, and don’t put any load on the battery for a few days and see what happens. You’ve got nothing to lose. If the voltage stays up past 12.6 overnight, then it simply means the battery was not being fully charged by the AC charger. It likely will not hold the 115 AH it did originally, but it might still work for some small loads.
We have a home that is completely powered by the wind and sun, has been for almost 10 years now. We made plenty of mistakes and learned a lot the hard way. My old system was simply 4 golf cart batteries wired for 12 volts at 440 amp hours, and it ran DC lights and electronics with a 150 watts of solar wired directly to it, no controller. It uses a bit of water in the summer when it’s near full charge on sunny days, but it has worked that way for years. If you’re going to replace the battery in the end, consider using two Trojan T-105 golf cart batteries instead of one from the marine place. They really are designed for that kind of service, will deliver more of their stored power and run longer for you, but definitely keep them charged up. That little panel is designed to keep a car battery charged while you leave the car for a long time, not for running any loads. Even on a sunny day, at 1.2 amps, you might store 6 or 8 amp hours, which translate to 4 or 5 you can draw back out at night, not a lot of power. It would be good for LED lights and maybe a radio, or a small intermittent load, like a drill or laptop.
A really good place to look for more info on all of this is Home Power Magazine. They really get into the nuts and bolts of solar, batteries and such. Our home’s small system was even featured in it years ago. If you subscribe online, you would have access to their archived articles for years past, and you could use their search engine to find an article called, “Starting Small.” There is also a great book at the library by Richard Perez called, “The Complete Battery Book,” that talks all about charging lead acid and other types of batteries, it’s worth reading just the lead acid chapters. I will list a few other places below you can google for more info. Good luck with that battery, and take care Brandon, Rudydoo
PLUG IN GRID TIE INVERTER
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