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Posted by: twilliams Sep 21 2016, 05:34 PM

I have a hard side camper with one battery. I would like to know how many solar panels will it take to trickle charge the battery and how many watts.

Posted by: towpro Sep 28 2016, 03:29 PM

Just sitting there my camper uses 1.5 - 2 amps I think.

P (power in watts) = I (current) X E (voltage).
batteries charge at higher than 12v, so I always use 13v in my math.

13V x 2A = 26Watts. But that is if everything is 100% efficiency and the sun is always shining. you have to figure in night time, cloudy days, etc. Plus you need to be able to charge batteries also.

so in theory, 100W divided by 13V = 7.6A.

But 100w solar panel through a PWM (cheaper) controller will really charge around 5-6 amp in full sun conditions. that will charge a battery slowly.

I run two 27 series AGM batteries, and have two 100w panels. I have seen upwards to 12A charging when batteries are around 75% charged.

I run Renogy panels found at amazon, but I have a Bogart Engineering meter and solar charger.
I am looking at a new camper, and solar goes with old camper, so I might do some things different, but I am happy with all the parts I have, but might spend my money different next time.

Posted by: twilliams Sep 29 2016, 02:37 PM

thanks for the info. I will try the math. amazon is a good site