Dead battery, not dead battery?

The 1UZFE EGR Delete Kit is available for sale here.


93 SC400 haven't started it in over a month, maybe more. Eitherway new battery about a year old, tried to turn over, no start... it skipped like the battery was dead, so I jumped it, ran it for 30 minutes and turned in for the night. Next morning, same problem, turns over, no start. OK, took the battery out and dropped it at the local auto parts store, in this case Oreilly's. They check the battery and state the battery is good, 12.6v. I asked them to charge it, and they hesitated, but did it anyway. Got it back dropped it in, good start, hasn't happened anymore. My question would be anything I need to look at? Charging system? I daily it now with no issues, besides the radiator. Thanks in advance.