Just to claify a few things.
All batteries have a power curve and it varies from model to model. Here is one for a standard AA battery. (e91)
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Flip to the second page and look at constant power discharge.
(I went through a lot of this figuring out what batteries would last longer in my GPS unit) The Energizer and e2 profiles are almost identical so the only thing you got when paying out the noze for an e2 was a warm fuzzy.
Anyhoo, back on line...
Feel like watching a slide show?
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Optima self-discharge curve.
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Hope that helps clear things up.
The only sure way to test a car battery is a load test. Most PepBoys and probably C-Tire (Tyre?) :) will have a setup. This is a computer that charges the battery then does a controlled and timed discharge.
FWIW, I've brought dead cell batteries back to life by using a charger (high amp) and a volt meter to bring the battery up to the service maximum 5-10 times in a row and then using a low amp trickle till all cells bubbled the same. I don't suggest doing this without eye protection because you will bubble the cells quite a bit and that's acid that is popping out even if you can't see the microsopic drops.