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diy solar

diy solar

field testing a battery banks "health"

pjstock

New Member
Joined
Mar 23, 2025
Messages
22
Location
Toronto
applying testing tools to my (probably 18 year oldtor ) GEL batteries I am getting:

1) from a load tester... a reading I cannot decipher
2) from a more fancy battery tester, on various battery type settings, generally a REPLACE or POOR reading

but can I field test this battery?

for instance, at 230pm this afternoon it was reading 13.02V
I have since run the 12v 42W refrigerator for... 6 hours and the auxiliary battery voltage has dropped to 12.44v
so down 0.56v

so, based on that, can I calculate the health of my GEL batteries?
 
Hard to tell with a fridge since it can cycle on and off, but you have the right idea for a real world test of a slow draw. Especially if you find a more consistent load. A slow draw test like that won't be the same as trying to start a motor though.
 
In general, multiple batteries that make up a "bank" should be separated for testing as individual batteries.
They need to be charged to full while monitoring temp, let rest for a few hours and then discharged at a constant rate, usually associated with the rated capacity "c" rate.

As mentioned above, 18 year old batteries are not worth the time to do it
 

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