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85 caprice blows battery cells

Why do the batteries keep blowing cells?I know its gotta be a bad ground.I cant find it.Had starter and alt tested and they both good.It just started doing this.

What do you mean by "blowing cells’? Where is the voltage regulator in this beast, in the alternator or separate? Has that been checked with the alt? What is the voltage across the battery terminals when at idle and when revved up a little?

I have bought a like 3 batteries for this thing.I took the first back to auto zone and they said it failed the test and was a bad battery.The next one I checked b4 I left the store and it was good till I brought it back and they said I might of blew the cells out of that one too.I can start it with a new battery but eventually dies cuz the battery goes out.Once it dies I dont have any juice.Its an 85 chevy caprice with a 305 5.0 V8.

What do you mean by “might of blew the cells out”?

If you have a volt/ohm meter, set it to read 20 volts AC. That’s right, AC! Start the engine and measure the voltage across the battery terminals. If you see AC voltage at the battery terminals, replace the alternator.


Sounds like either your alternator is overcharging or the brand of batteries you’re getting leaves much to be desired.

This sounds very much like an over charging issue and I must wonder how repeated trips to a parts house with this seemingly simple problem leaves chry guy still wondering. Even a high school kid who gets greasy regularly and works part time at McParts should recognize such a basic problem.