Low Voltage on Batteries

Dennyha

Well-known member
For my system, I have four 6 volt batteries, each one is 240 amp-hours. They are wired in series-parallel for 12 volts, and a 480 amp hour total capacity. My system is 400 watts on the roof, a Trimetric battery monitor, a Bogart Engineering controller, and a Go Power 2000 watt PSW inverter.

I very closely follow my battery status using the battery monitor. This past weekend, I noticed that when I would get down to about 75% of battery capacity, my voltage was down to about 11.7 volts. I've always heard you could discharge down to no lower than 50% of battery capacity safely. Why is the voltage dropping so much. My four batteries are Crowns, purchased directly from the factory in Ohio. I check the water level regularly, and fill to the appropriate level. I've never had the level in any cell get anywhere close to exposing the plates.

Is this normal?
 

Dennyha

Well-known member
Thanks Dan. I'm going to check each of the four batteries individually to see if one may have a bad cell.
 

Silverado23

Iowa Chapter Leaders
Make sure that you are testing without a load. Running a load can cause the voltage readings to drop significantly.
 

Dennyha

Well-known member
Make sure that you are testing without a load. Running a load can cause the voltage readings to drop significantly.

Actually, there was probably some load on the batteries when I read the 11.7 volts on the battery monitor. Perhaps that's my problem?
 
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