I think that Loren's advice about being cautious about wiring dissimilar
batteries in parallel is worth considering. it is Received Wisdom and one
should not go against it without accepting potential ugly outcomes.

But . . . not much is likely to go wrong if they are the same technology
(e.g., sealed, AGM, gel, deep-cycle, whatever); and considering that folk
routinely connect different tech batteries in parallel with their fancy
Surepower 1315 or similar separators for charging which driving (starter
battery + deep cycle, for example) then discharging, esp. at the low rates
that one typically sees in normal Westy Life, should not cause much
trouble, either.

The one area I might be cautious about is leaving dissimilar battery types
connected together and running off one "smart" charger. This could flummox
the charger's smarts which might lead to one battery being less happy than
the other. Or two unhappy batteries.

Is my seat of the pants guess, anyway.

--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
Bend, OR
KG6RCR

On 10/28/2009 10:56 AM Loren Busch wrote:

> On Wed, Oct 28, 2009 at 10:43 AM, Timmy Evens <monkey_lips@yahoo.com> wrote:
>
>> i'm installing a DC 0400 Norcold fridge in my 83 westy. t
>>
>
> The way you put that it sounds like you are planning a second aux battery
> under the back seat in parallel with an existing smaller battery already
> under the drivers seat?  If so most wisdom regarding batteries says not to
> parallel batteries that are not identical.  For my Norcold I have just one
> aux battery, a Group 31 AGM, under the back seat.  The Norcold is wired
> directly to the aux battery and so is an inverter and other stuff.  I have
> not been aware of any problems with the Norcold because there are other
> items running from the aux battery.
>