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Old 02-16-19, 02:13 PM   #20
BillG
Lurking Renovator
 
Join Date: Jul 2016
Location: Minneapolis
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Quote:
Originally Posted by Robaroni View Post
I don't believe there's any place in the lower 48 that doesn't have sufficient sun for 10 days straight. Also 50% is too low a discharge point it reduces the max battery cycles appreciably. My home system is designed for 75 to 80%.

Two 75 aH group 24 batteries will run about $140 each, he's just lighting a 5 watt LED. His moniker is Poor Man!
Well, a 75% cutoff would then require (4) 24 series batteries. That is too many to safely wire in parallel, in my opinion. I agree that the battery will last longer, but suggest using batteries designed for the job, not car batteries. If he can live with 5 days of autonomy, then he could use two batteries set up for a 75% cutoff. It is my understanding that these are security lights, so it is important that they stay on at night. As I'm sure that you know, a big bird splat will all but shut off the output of a small panel, so that would give him 5 days to find it and squeegee it off before his security lights no longer work.

For what it is worth, my array has not produced more than 8 or 9 Watt Hours per day for the last 11 days according to its monitoring system, and I don't expect the snow to melt off of the array for at least another week, and probably two or three weeks.
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