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Old 02-18-19, 07:08 AM   #24
BillG
Lurking Renovator
 
Join Date: Jul 2016
Location: Minneapolis
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Good. We agree on one thing. The 30 Ah battery, utilizing 25% of its charge, is 90 Wh, not 225 as previously stated. 90 Wh is only enough for one single night, and will fail if there is a cloudy day.

I'm not as optimistic on the panel output. From PVWatts (a free online calculator from NREL), a December day will average 141 Wh, and a July day will average 346 Wh. Yes, it is enough to charge the battery on a perfect day for one single night of use, but just barely, and will fail to provide a single night of charge to the battery in December if there is a less-than-perfect day, or if the panel gets dirty. This assumes an MPPT charge controller, because a PWM controller would provide quite a bit less capacity.

I'm not intending for this to be a pissing match, but I'd hate for the original poster to purchase the system based on incorrect assumptions or wrong math, and then have to buy it again. It is always less expensive and more satisfying to do it right the first time.
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