# I have a 60w solar panel and a 12v large deep cycle battery, how do I get it to charge faster?

From total discharge (11.65v) the battery charges to 12.03v in one day, 12.24v the second day and 12.26v the third day (all sunny days). I have the solar panel (I built) hooked directly to the battery (there are blocking diodes in place). The panel tops out at 17.5 volts or so (using 36 1.8w cells). I know the panel delivers charge, take the 12.26v reading as a baseline, if I plug in the solar panel it jumps to 12.34 volts. So is there anything else I can do to increase the efficiency of the charging at this point?

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Hey Savage, Jeff is right on the angle, but I imagine if you've built the panel yourself, you're tuned into that. I'm guessing that your panel does not have the amperage to push that deep cycle battery up very fast. Lead acid batteries go through a charging voltage curve, the volts curve up quickly at first, and around 12.6 level off until you are above 90% state of charge, then you see much higher voltage as the battery begins actively gassing at the top end of its charge cycle. Starting at 11.65 volts, if you battery is 50 or 60 amp hour, and your panel is putting out 1 amp, you will need about 12 sunny days to get to full charge. Have you checked your short circuit current on the panel? Take an ammeter, unhook the panel from the battery, set it in the sun and put the ammeter across the output wires. If your completed panel is 2 square feet, you might see 1.5 amps. You can get your panel wattage by multiplying the open circuit voltage by the short circuit amperage. 18 volts, and 1 amp would give you a 18 watt panel. That panel will take a couple weeks of sun to bring that battery up to full again, and then you will see voltages above 13.5 while it is charging. There isn't any magic elixer that will improve the efficiency of your solar cells. Silicone cells are around 10 - 13 % efficient, that's all the chemistry will convert. Some people have tried using mirrors to focus energy on them, but they just overheat and get damaged that way. You can't change the physics.

There is a great book at the library by Richard Perez called, "The Complete Battery Book." I read just the chapters about lead acid batteries and skipped over the litiums, nicads and so forth. Richard also happens to be the editor of Home Power Magazine, a great periodical on solar, wind, hydro and other home made energy sources. Using his information and going to a couple energy fairs years ago got us where we are now. Our home is completely powered by the wind and sun, has been for almost 10 years. It's been interesting and fun, and we made plenty of mistakes, but we made it here anyway. There are also some great non profit groups with websites you can learn from, I will list some names below. Good luck Savage, and take care, Rudydoo

Source(s): Homepower.com Solar Energy International Midwest Renewable Energy Association Great Lakes Renewable Energy Association The Complete Battery Book, by Richard Perez American Wind Energy Association
• Hannah
Lv 4
4 years ago

The PC will use only 150 watts unless you run a gaming graphics card, then the wattage will be 300 watts. So 150 watts x 3 hours is .45 Kwh per day. The lathe uses 745 w / 2 = 372 watts. So 372 x 1 = .372 Kwh per day. Total = .822 Kwh per day. The solar panel needs to be at minimum .822 Kwh / 8 hrs sun = 103 watts capacity. But since the battery, inverter, and solar strength are not 100% efficient, figure about twice that size. A 200 watt panel should work. Use a deep cycle battery of around 200 amp hrs for storage.