Is this the stock Dometic fridge? If it's wired OEM
it shouldn't affect the battery; engine has to be running for it
to operate in 12 volt mode. Sounds to me like
the aux. battery is low and is a load on the starter battery
given that there's no relay installed.

What loads would typically be on the aux. battery?

Though it would require diligence on my part to make sure
I operate the switch when needed, I've been
giving thought to installing a battery switch in place
of an isolator for the aux. battery. (kill 2 birds; battery kill
switch and isolator in one?)

Neil.

On 7/4/15, PB <pbrattan@gmail.com> wrote:

> For the past few days, I had the van plugged in and was testing the
> fridge.  I might have accidentally had it on the wrong setting because when
> I unplugged it and turned the key, the battery was very low, but not dead.
> It's probably time to replace the 8 year old battery, so what is the best
> choice?  (That battery was bought in a hurry, so don't know if it's the
> best fit for power and physical size.)
>
> Also, I now know that I never had the aux battery relay system.  I just
> have an aux battery, and it's a little too large for the compartment it's
> in. At some point within the time of a battery's life span, I plan to have
> the relay system installed and get some solar panels.  I don't want to have
> to repurchase any batteries due to poor planning.

--
Neil n

Blog: Vanagons, Westfalia, general <http://tubaneil.blogspot.ca>

1988 Westy Images <https://picasaweb.google.com/musomuso/New1988Westy>

1981 Westfalia "Jaco" Images, technical <http://tubaneil.googlepages.com/>

Vanagon-Bus VAG Gas Engine Swap Group <http://tinyurl.com/khalbay>