Originally Posted by Linctex
Originally Posted by user52165
Tested it how? With a carbon pile load tester or something else?
Correct,
a tester that simulates a cranking/starting load (about 150-250 amps) is the only way to ACCURATELY test a battery.
" 12.8 volts - it's good! " .... really means nothing at all when the battery isn't under a working load.
I have one of these: Sun VAT-40
https://www.ebay.com/itm/SUN-VAT-40-5-available/253627133857?hash=item3b0d5aefa1:g:VmgAAOSwk3Fa~GH~:rk:3
f:1&frcectupt=true
Old school is still good school. Or the nearly similar Snap On MT552 (which now owns Sun), Typical selling price is about $150 without cart. Be sure it has the inductive pick up - green cable. Test battery, alternator, and starter with a real test, ON THE CAR .,,,,,,,,,,, very quickly.
Lots of good videos on You Tube on these.
"Computer Test" is nearly always junk test.
There are good modern ones but seldom used by selling stores ($$$$).