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Author Topic: Solar on the cheap?  (Read 15079 times)


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  • Posts: 121
Re: Solar on the cheap?
« Reply #30 on: July 18, 2011, 10:14:16 AM »
Well, I guess my batteries aren't up to snuff. I turned off the fridge and disconnected all hot wires between battery and RV. I left the 45W solar panels hooked up for a week of sunshine. I checked last night in partial sun, about 6:00 pm, and the charge controller was only showing 12.8v. I checked the water level in the batteries last week and it was good. I guess my batts won't charge beyond about 12.8v. Fortunately, my weekend usage seems to be light enough that I haven't run out of power yet. Maybe when I pull the batteries for the winter I'll have them hooked up to one of those desulfiting battery chargers and see if that will bring them back.

Thanks for all the help.
1997 Salem 30' fifth wheel; 2000 F250 7.3 diesel; 1996 Four Wheel Truck Camper
Northern California


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  • Posts: 1297
Re: Solar on the cheap?
« Reply #31 on: July 18, 2011, 04:37:58 PM »
You should do an energy budget.  Figure out how much each of your devices, including inverter and laptop charger, consume while running and how long each run for.    Note that an inverter consumes some milliamps even when nothing is plugged in and it's turned on.

Now figure out how much energy you calculate is coming in via the solar panels.   You will need to know the length of time you get reasonable strength of sunlight for your latitude.  Also realizing that cloudy days mean about 15% of the energy.   You should also calculate the angle of the solar panels to the sun.   You may be getting as little as 50% efficiency given that they will never be directly pointing to the sun.