At 11:53 PM 9/22/2003, Loren A. Busch wrote:
>If you have the right isolator the isolator takes over the business of
>regulating the voltage to both batteries, in fact the regulator in the
>alternator is disconnected. This eliminates the problem of a voltage drop
>and consequent low charging voltage on the aux battery.  see the following:
>  http://www.geocities.com/harald_nancy/dualbattery.htm

That's not quite right, Loren -- the regulator is still required.  The
effect of Harald's modification is to allow the regulator to see the
voltage actually appearing on one of the batteries, instead of the voltage
upstream of the isolating diodes.  This causes the alternator to raise its
output voltage sufficiently to compensate for the drop across the isolator
diodes so the battery charges as well as it would without the isolator in
circuit (except for the losses in the isolator itself, which amount to
about five per cent of the total alternator output).  Note however that the
regulator itself is still an automotive type which is best suited for
keeping a fully charged battery topped-up, and is quite *un*suited to the
task of actually charging a discharged battery.

david

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"