HHL said:
I do have one of those testers... Also thought they are a great idea, mine even tells me what the internal resistance is in milliohms... great, until the battery in my big car died....
After I replaced it, I decided to recharge the old one and this gadget pronounced it good even though it can only sustain a 2 amp load for about 15min..... so, not sure what the algorithm is to pronounce a battery good or bad.. it sure is not reliable. I don't trust it any more and have gone back to old one that puts a 100A load on it.
I take it that you set all of the parameters (CCA, battery chemistry, etc) properly in the tester? Which one do you have? I'd like to avoid getting that one. Maybe I should also pick up a traditional 50-100A load tester too. I wonder if you had an individual cell just conk out, as opposed to the entire battery's aging process contributing to its demise.
Then again, if we look at how load testers work https://batteryuniversity.com/learn/archive/why_do_different_test_methods_provide_dissimilar_readings the ones that don't draw a large current tend to rely on capacitive and inductive components inside the battery to get their readings. So I'm not sure how they could possibly get a good reading when the battery terminals are still attached to the vehicle, if there are capacitive and inductive components in the vehicle too.