General > General Technical Chat
Car battery tests are of no value
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GreggD:
My neighbor had trouble starting her car yesterday. Took it to Autozone (store) for testing.
They load tested the battery and said it was fine, must be a problem with the starter.
Three hours later the battery was dead. You know, click-click-click.
There was no load left on just a 7 year old battery and they fail suddenly.
rstofer:
Around here during the summer it's HOT!  Car batteries don't like high temperatures so it is not a surprise when they fail during the summer.

Of all the batteries I have replaced over the last 30+ years, I would bet that every single one was replaced during the summer.

Seven years on a battery is pretty exceptional.  Even with quality batteries, I only get about 5 years.
BradC:
I wouldn't say they have no value. Simply the test you used was not suited to showing up the failure mode you have. Generally a high current load test will weed out most failures in a lead acid starting battery. It sounds like yours has high internal discharge.

rustybronco:
It all will depend on the machine used and the operator of it.

ConKbot:

--- Quote from: rustybronco on July 20, 2017, 03:48:47 pm ---It all will depend on the machine used and the operator of it.

--- End quote ---

+1 to that. I've had an alternator tested at autozone after the car was giving symptoms that are alternator related. (Brake light and battery light, weird quirk in the older sentras) and the trash computerized tester gave it a pass in 5 seconds. Took it to advance auto parts, they put it on a tester that had meters and required the operator to know what was going on. 20 seconds after it was turned on, the regulator warmed up, voltage shot up to 20V, bad regulator confirmed.  :palm:

That being said, a battery test is usually charging the battery, and put a cranking load on it and see if it can deliver the cranking amps needed. Won't identify one not holding a charge.
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