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Re: battery capacity

To: Denise Thorpe <thorpe@kegs.saic.com>
Subject: Re: battery capacity
From: Len Bugel <bugel@miranda.fnal.gov>
Date: Tue, 5 Dec 1995 16:34:56 +36000
An electric 1100 sounds like a great idea! You could even cover the roof 
with solar cells.
        I have been trying to restrain myself on this battery thread, but 
it finally got to the point where I just had to stick my oar in the 
water. I have a solar-electric 12V system in my house in Vermont. My 
(deep-cycle) batteries are sitting on a wooden platform a foot above the 
concrete floor - I have always heard the concrete story, with no 
explanations that made sense, but why take chances. To get the best 
estimate of the state of charge of a battery by measuring voltage, the 
measurement should be carried out at some known level of load, or current 
draw. "Home Power" magazine published a graph of state of charge vs. 
voltage at various rates of discharge, and I have the graph in Vermont, 
but unfortunately I am spending a sabbatical year in Illinois, and my VT 
house is rented! I think  with no load connected to the battery, the 
voltage doesn't start to drop much until it is pretty well drained, but 
under a reasonable load, the voltage is a decent indication of the level 
of charge. Even a "dead" battery will show a voltage above 11 volts at no 
load, though. Wish I had the graph handy so I could be more specific.

        Len Bugel
        '50 TD  (newly acquired, and stored for now)

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