<ALL> Maintenance-Free Batteries

[ingraham@xxxxxxxxxxxxxxxx (Curtis A. Ingraham)]

Earlier it was writ:

> I skimmed through an article recently that talked about 
> attempting the use of "std" maintenance-free batteries on
> BMW's. The article talked about the batteries being different
> to what BMW normally puts in their cars and that the alternator
> not being set up to charge such a battery. The output voltage
> the alternator is set up for would not be enough to charge 
> such a battery. 
> Is this true? I don't mind paying the price of the "real" 
> battery, just want to find out the "real" story. 

That article surprised me.  I think the claims were true to some
extent, but not to the extent that we should routinely expect
all maintenance-free batteries to remain partially charged in all
BMWs.  I have used several kinds of maintenance-free and sealed
gel batteries in several BMWs and other cars, and I never noticed 
any of them to stay partially charged (based on measurements of 
charging voltage, charging current, specific gravity, and load 
tests).

Later it was writ:

> AFAIK a battery is a battery is a battery. 

As to charging characteristics lead-acid starting batteries are 
pretty much interchangeable.  Other kinds of batteries exist, 
however, and have different materials, different chemical processes, 
different construction, and different charge and discharge 
characteristics.  Some of these are marketed for auto use.

Curt Ingraham
'72 2002tii
Oakland, California

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