Diehard Platinum AGM at 12.4

[Max_Power 10+ year member]

I have a 1 1/2 year old group 65 diehard platinum that is giving me problems. Over the past weekend I put it on a "smart charger" @ 2 amps. The charger is supposed to charge and then float depending on the battery condition.

Over 2 different charging sessions, it gave me an error of "battery will not accept charge after 18 hours" and "battery has open cell".

I checked the resting voltage today and read 12.4 which to me is NOT fully charged. I took it back to sears and they checked it, charged it and it said good battery but still rests at 12.4.

I have a DC power alternator and when running, my car when warm will only charge at 13.8 volts.

Am I missing something here?

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[gckless 5,000+ posts]

Yes. The warranty. Take it back and exchange it.

 

[Max_Power 10+ year member]

This is where the problem lies. I took it back to sears expecting an exchange, but they put my battery on their diagnostic/charger machine which said my battery was "good". Got it back to my car, checked it again even with a surface charge it said 12.4 Volts.

They would not give me a replacement.

 

[hispls 5,000+ posts]

This is where the problem lies. I took it back to sears expecting an exchange, but they put my battery on their diagnostic/charger machine which said my battery was "good". Got it back to my car, checked it again even with a surface charge it said 12.4 Volts.
They would not give me a replacement.

If it load tests good it is good. A car battery is designed with six 2.1V cells in it. So the target is resting voltage of 12.6, and they should be charged at no more than 14.4V. If you are only charging at 13.8 than it has to do with your voltage regulator and not a faulty battery.

 

[Max_Power 10+ year member]

I guess I wasn't being clear. These are 2 different issues. and the battery will only rest at 12.4 despite being on a charger for an entire weekend.

The charging problem I assumed was due to a regulator in the car or alternator itself. I would like to know why its put there instead of the 14.4 we are all trying to achieve.

But my problem with the battery is unrelated to the alternator, at least I think so. 12.6 is a fully charged battery. I have other batteries that sit on 12.9 and 12.8 regularly. I paid $230 for this battery, why can't I get full performance out of it, or charge it.

Am I asking too much? with the car running and without accessories on, I would like to see a solid 14 volts or higher. with the car off I would like to see 12.8 volts like almost every other battery I have.