Testing a Battery

[SlinktRR]

Ive had my die hard 800cca battery for 4 years. It usually sits at 12.65V, 13.8 running. I have been driving the car back and forth to work all summer so it's getting a nice workout. The other day I left the parking lights on for 10 hrs and drained the battery to 11.91V at the battery posts. To my surprise it started right up and the ammeter was pegged, usually the ammeter needle bounces from the voltage regulator so it was clearly charging. I drove home and let the battery sit, it had charged up to 12.1V. Next day I started up and drove back and forth. Now up to 12.4V.

Should I just replace the battery? It was discharged badly, definitely dies hard but it is holding a charge well. I will put it on the battery tender to trickle charge. Any other tests I can do?

 

[Darthomas]

Be happy, the battery, voltage regulator, alternator and ammeter are all working perfectly! You presumably got to watch the charge rate taper off as it should.
A deep discharge does not damage a battery if you charge it right back up as you did, letting it sit in discharge for days would cause sulfation to clog pores in the plates, limiting available current capacity for cranking.
You're fine.

 

[RT K_line]

As long as the battery doesn't drop below 9.6 volts under a load it's good. You can test it by turning on all The accessories, fan,lights,ect. And have someone start it while checking voltage with a meter. Or just take it to sears and have it checked. 4 years for a battery is about it for mosT batteries though. 17 years experience working at sears myself.