charging voltage across the battery with full load?

[steve]

What should the typical charging voltage across the battery with full load at idle? I.e. with the car running, and everything on, headlights, AC, fan on high, radio on, rear defrosters going.

 

[chris2523]

depends on how good the battery is, how good the alternator is, wiring, how hot the alternator is cuz when they heat up they put out less. its hard to say.
your shooting for 14.4 at idle with a light to moderate electrical load. 14.4 is basically perfect.
but the fan, ac and defroster are all huge drags on the alt. you can quickly outrun the alts idle charging ability, which is maybe half its total output. so you're looking to stay above 12 at idle. 13 to 14 when above idle, driving around.

lots of marks have had problems idling too long with several accessories turned on. they run out of juice.

 

[J]

 

[maxmk8]

I think 13.7 if my memory serves me right.