Battery capacity (CCA) lowers after charging new battery

Joined
Aug 29, 2018
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519
Location
Central US
I just bought two new "Group 24 550CCA Flooded Dual Purpose Marine & RV Battery", and is my habit, I connected them to chargers. Both batts had water levels as expected.

Before charging, one battery measured 760 CCA using a Solar BA-9. The other measured 675. After charging, the 760 dropped somewhat, but the 675 dropped to 470. (I made sure the BA-9 had fresh, clean lead to measure from on the posts. I've used the BA-9 for a decade, and am sure it is working properly).

I charged them using the flooded lead acid setting, and 2 amps charge program, so they should not have been overcharged.

The next day, I charged the low battery again, and now it is showing 650ish CCA, as expected.

Has anyone seen anything like this, or have any explanation?
 
Charging creates bubbles on the plates. Its possible that reduces the surface area that the plates interact with causing a reduction in available CCA. Try rocking the battery around some to break loose those bubbles, then test it. If it's bubbles causing the reduction, the CCA should go back up after the bubbles are gone.
 
Those capacitive testers are not foolproof.. maybe one of your leads is getting old/bad connection?
I actually just bought a second one for the basement batteries, and it agrees within a few numbers of the old one. Good idea, though!
 
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