Acceptable resting battery voltage for new alternator?

[oldskewel]

No doubt you are just fine. Nice work on all that other stuff "while you were in there."

Does anyone have any theories about how using a new alternator to charge a weak battery could "risk limiting the life of the alternator." The only one I can think of is that if you try it on a dead battery and it won't charge because the battery is dead, and the owner incorrectly thinks the alternator is bad, and takes it back to the store, yes that would limit the life of the alternator. But other than that ... ???

Also, whenever you measure voltage, especially in these cars, it does matter where you measure it. Measuring at the battery jump ports in the engine bay should equal V at the battery posts. But that voltage will be higher than any system voltage read off a wire, or by the computer or any gauge you may have installed. Usually I think about 0.3-0.4V lower on the BMW displayed voltage vs. the jump ports. And that's for battery (engine off) or alternator (engine on).

[mtthmpsn]

Originally Posted by oldskewel

No doubt you are just fine. Nice work on all that other stuff "while you were in there."

Does anyone have any theories about how using a new alternator to charge a weak battery could "risk limiting the life of the alternator."

Thanks for the quick reply. Yeah, the alternator install was a breeze compared to the other stuff. I did take my voltage reading from the dash, but confirmed it was in the low 12's with a voltmeter at the battery.

I read up a little more and the theory anyway is that a weak battery will cause the alternator to "work harder" to get it back to required voltage. Apparently, the same reason you shouldn't use a running car to recharge a dead battery - what I read recommended always recharging first with the alternator's only objective to maintain charge. But also reviewed some posts and 12.1v isn't uncommon among BMW owners.

The battery is only about a year old. That said, it did die due to the alternator issue and I had to recharge to check the alternator so may have hurts some cells. Might try and take it back anyway since it's still under some type of warranty.