Since the positive wire from to the aux. batt. comes from the main batt., the
volatge regulator prevents over-charging the aux. batt. the same way it
prevents overcharging the main batt., plus the main batt. gets charged
first.  This has been debated in the archive, and that's the consensus.  My
set up has been fine.

The real concern is to make sure you re-charge your aux batt as soon after
you use it as you can, and as fully as yoy can...doing this will ensure max.
life.  Failure to do this can cut life by over 1/2.  As soon as I get home
from a campout, I plug my aux batt in for charging.  Unless I've been driving
for 4 + hours, it always takes more charge when I get home to get up to full
re-charge than what the van charging system provided while driving.
Steve

Steve Manning wrote:

> Do you allow the aux battery to charge all the time???. I was told that's
> the way you can kill a deep-cycle battery prematurely; by overcharging it
> before discharging it.
>
> I only use the stock camping relay with a 32 amp deep-cycle battery and
> I'm concerned about burning the battery out from overcharging. I don't
> switch it. I
> use the relay as the isolator. All the camping stuff is after the relay
> and the aux battery.
> -steve-