battery madness

[josiahg52]

Originally Posted by Just Looking

I have a new AGM battery installed but not registered yet. Should I be concerned about the upcoming 25 hours of freeway driving that the alternator will be over-charging the battery?

Thanks in advance for sharing your expertise.

I would not be. That being said, I don't know how the charging system operates in our X5s. Does it look for a certain current value at a set voltage or is it a simple matter of charging back a certain number of ampere-hours at a programmed charge voltage. If the latter, I would not be worried in the least where relatively there is some small risk involved with the former method. In either case, 25 hours should show little affect to the life of the battery.

In short, I don't think this "stupid" charging system is capable of "frying" a battery unless there is a defective or malfunctioning part. Certainly optimized charge profiles for the battery type will maximize the life of the battery by maybe +/- one year. For a battery that already has a lot going against, that's hardly noticeable. Surely if you're going through battery/ies at less than four year intervals, something is wrong.

The FLA battery in my M5 is an OE BMW battery by Exide is nine years old and has never given me an issue. I've noticed that in the last three years capacity has dropped about 9% but it still provides enough cranking amps for me to feel comfortable leaving it installed. Besides ,the M5 is a summer car and I don't sit around with the ignition on and engine off. .

On the other hand, the AGM Red Top Optima battery by Johnson Controls in my Tahoe has been in there since 2008 and still routinely tests out very close to 100% and provides ample cranking amps. I've been given many "bad" AGM batteries which I have recovered to 100% capacity. The AGM design is robust and resistant to damage. Is it the best? I don't think it's as cut and dry as that. Johnson Controls and the Interstate Megatron batteries are FLA and they are superbly exceptional.