House battery voltage under draw?

Almot wrote:
Depending on your alternator and how it is wired, driving half a day can be better than plugging it in 20A overnight.

It certainly works very well using the Ford E450's 130 amp alternator in our Class C motorhome.

At cold start at idle the alternator can temporarily dump 70-80 amps into our 230 AH AGM deep cycle battery bank with it's voltage above 14.X volts. When we travel, the alternator's voltage slowly drops to 13.5 - 13.8 volts as the chassis and coach batteries charge and as underhood and outside ambient temperatures rise. The alternator's voltage only goes below around 13.5 volts in high outside ambient temperatures - usually from about 90 degrees F on up ... which is perfect for liquid or AGM lead acid batteries because all charging voltages should be reduced as ambient air temperature around the batteries increases. The alternator gets our coach batteries charged to where they are not accepting any current in 3-5 hours of driving - depending upon how low the coach's AGM batteries were when we started.

I can watch all this happen as we travel because I have chassis battery and coach batteries digital voltmeters on the cab dash, in addition to a digital ammeter on the dash indicating current flow into or out of the coach batteries (negative readings for current flow out of the coach batteries and positive readings for current flow into the coach batteries).

AGM batteries with their low internal resistance, combined with whatever Ford and/or Winnebago seem to have done, is working out well.