Geza Polony typed:
> Here's another wrinkle in the whole equation (to mix a metaphor): the
> voltage regulator/alternator system doesn't seem to be adequate to keep the
> batteries charged.
>
> Under load (fridge, AC, headlights, etc. on) my system barely generates 12.3
> volts at the vehicle battery, and about 11.8 at the aux battery. This is
> with a rebuilt alternator and new vehicle battery (a week old on both.) With
> no load, voltage is normal, about 13.8- 14 volts.
>
> In other words, there's not enough voltage to charge the batteries, no
> matter how you configure them, while driving.

If you're losing 13.8 - 12.3 = 1.5 volts between the alternator and the
vehicle battery when the lights and stuff are on, then either the
alternator ain't regulating (measure the voltage at it, rather than the
battery, under your test conditions to see) or the wire between the
alternator and the starter battery is too skinny. Another 12.3 - 11.8 =
1/2 volts being lost between the starter battery and the aux battery is
a sure sign of not enough copper. Fatter wire.

--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR