[Ray,IN]

My 92 began doing the same last month. I had Interstate check both OEM batteries, the guy said both tested good.
Two weeks later-dead again. I returned to Interstate, this time watching the guy test batteries. He never disconnected both batteries, only one gnd at a time, same procedure when replacing each. He stated this was normal procedure and completely accurate. Anyway, both OEM batteries were shorted.
That's when he told me buying higher CCA batteries than OEM size was a waste of money. Stopped by my local Chevy service dept. and asked service manager (who BTW recommended Interstate batteries) about battery CCA. He verified the OEM size comment by Interstate guy this way:
"Larger CCA batteries, in the same size case always have thinner components packed into that same size case, which can mean premature battery failure or shorter lifespan".