Battery Charging

[Maine Sail]

...just sitting there idling, daytime running lights, but everything else off, even the radio.

Could be the difference is the DRL's unless BMW/ (likely a Bosch) changed the regulation voltage. Our M3 did not have DRL's.

Tested a Subaru, Honda Piliot and Toyota Sienna last evening and all were between 14.3V & 14.5V, which I find to be pretty normal. Usually I see a range of a low of 14.2 to a high of 14.6 on cars but 14.0 is certainly a reasonable voltage and means the alternator is working..

 

[jviss]

...14.0 is certainly a reasonable voltage and means the alternator is working..

Well, that's good to know!

I wonder if this is one of those set-ups where the ECM is controlling the regulator output; I've read (online somewhere) that some cars are set up that way.