Dead Optima Battery, No Start but Good Voltage (11.5V)

Hey fanatics,



I'm having trouble with starting my car since weather is going crazy in Dallas. It was starting perfectly last night, now it doesn't. It's truly wonderful that you can experience four season in a week...ffs.



Anyway, battery I have is an Optima RedTop battery. It's only 3 years old, still producing good voltage (11.5-11.8V when cold). Charging is not an issue as it produces output of 13.7-13.9V. I haven't had a chance to see the battery output when I turn the key, as it would give me some sort of indication what's wrong with it. Oh, I took it to O'reilly two weeks ago when it died, they said battery is at 80% capacity.



Here's the things I tried and checked;

a) Battery/alternator output.

b) Battery charging capacity.

c) Parasitic draw test.

d) Jump start, of course.



Things I haven't tried and checked;

a) Desulfation.

b) Internal impedance.

c) Replacing, of course.





So, given the fact that battery voltage is in acceptable range, and charging capacity is compromised, what would be the problem? I understand that AGM batteries are easier to be rejuvenated with proper equipment such as AGM battery charger capable of desulfating, every auto part store I contacted had no such equipment. (Haven't tried PepBoys and NTB.) Would this be a simple sulfation issue that can be resolved without replacing the battery?



Let me know what you think!

Thanks in advance :hi: