RE: [VAL] 12 volt refridg

["dtidmore" <dtidmore@xxxxxxx>]

Dan,
First off, Dometic does make a 12/110/gas combo unit in a 3 or 4 cu ft
models.  The issue with 12V is that it will deplete a battery in fairly
short order.  When A/S actually offered the 12v option, they had it running
directly from the car electrical system and THEN ONLY when the engine was
running. 

On the current Dometic units with 12v option the power drain is 15amps,
which requires 10 gauge wiring if under 17ft from the battery or 8 gauge
wire if under 27 ft from the battery.  Dometic STILL shows connecting
directly to the car electrical system with a relay that connects ONLY when
the engine is running and it REQUIRES both dedicated positive and negative
wires running directly back to the battery. 

If you choose to run on trailer batteries, understand that the 12v option on
the fridge can totally drain a typical deep cycle battery in about 8-10
hours of operation.  Now that assumes continuous operation and if the fridge
is cold and the weather is mild, it will cycle, extending the battery life.
Also, if you tow with a truck, you could make a battery bank of several
batteries that road in the truckbed, charged by the truck charging system
(but disconnected when the engine was off) and connect them to the trailer
via an upsized charge line (ie it would put the extra batteries in parallel
with the trailer batteries which would give you a big jump in available
battery life).  Charging those batteries with the tow vehicle electrical
system would work, but it will take several hours of charge time (even
assuming high charging currents) to replace what the fridge required during
a typical 24 hour period.  Using a genset such as the Honda EU2000 to charge
the batteries during the day would be a much better solution.

As for being hard on the car's charging system, not anymore so than running
the car AC or any other higher amperage systems.  If your alternator is
undersized (ie not upgraded with a towing package), you might want to
replace it with a 100 or 150 amp alternator, but that is not difficult.   

An alternative to going to a 12v fridge is to install a 300W dedicated 12v
to 120v inverter so as to allow the fridge to run on 120V full time.   This
does NOT change the drain on the batteries as the amperage involved will
actually be slightly higher requiring the same gauge dedicated wiring to the
inverter as would a 12V fridge.

Hope this helps. 

david