Hello,

I have had several discussions with Bob Hoover on this subject, and while he is certain, I am not.

The issue is whether the Motorola alternator/regulator senses voltage remotely or not.  Bob Hoover says no, I say I just don't know.

1) No remote sensing.  The output terminal of the alternator is regulated
   to the voltage necessary to fully charge a battery.  This is somewhat
   temperature dependent, but usually taken to be 13.8 volts.  If this is
   the case, there seem to be two options:

   a) Rather than using a diode battery isolator, use a solenoid switch
      that connects the aux battery across the base battery only when the
      engine is running.

   b) As was mentioned in a post sometime ago, there may be an internal
      connection in a Motorola alternator that can be used for remote
      voltage sensing.  If so, connect this to the base battery and use a
      diode type isolator to automatically route the charging current to
      both batteries.

2) Remote sensing.  If it has it, it would have to be through the idiot
   light wire, since this is the only other wire on the alternator.  There
   are a number of other cars that do exactly this, so it isn't far
   fetched.  However without a schematic of the alternator/regulator, I
   just can't tell.

   The advantage of this setup is that the real battery voltage is sensed,
   the resistance of the wiring harness need be of no concern.

   If this is the case, either type of battery isolator will work just
   fine.

So, can anyone verify what the Motorola system does for sure?

Thanks,
Mike    '84GL