To at least get you flying, go for the standard group 41 starting battery
which will give you ~60 A/H until you fry it. Depending on frequency of use
you may go a whole season.
The next decison to a real battery is where to put it. From experience you
probaly need at least 100 A/H to get through a weekend especially running a
heater. The 2 golf cart battery (~200 A/H), approach will give the best
combination of capacity and life.

Dennis

>From: Troy <colorworks@GCI.NET>
>Reply-To: Troy <colorworks@GCI.NET>
>To: vanagon@GERRY.VANAGON.COM
>Subject: Battery Woes/Choice
>Date: Thu, 22 May 2008 12:59:36 -0800
>
>I've been spending a lot of time lately charging, testing and retesting
>reserve battery capacity of my odyssey 1200.  As one person mentioned last
>week, the best thing about odyssey batteries is their advertisement;)
>
>In terms of reserve capacity (AH) I"m told the better way of determining
>actual AH rating is to take the reserve time (in mins) x 25 amps and divide
>this figure by 60. In the case of the odyssey that's about 33 AH. It's
>rated at 44AH. That figure assumes you're going to run the battery all the
>way down to 11 volts or less, which from what I've learned is not a good
>thing to do-- at least if you want your battery to last any length of time.
>
>The figures I've heard are ideally 50% discharge, but as much as 65%. A
>resting voltage of no less than 12.2 or so. I just did a test last night
>running my  Vitrifrigo C51 for about 13 hours. The best I can figure, this
>refrigerator runs about three minutes out of every 10, so I rounded that
>off to 20 minutes out of an hour. That works out to about 11.2 AH.  In
>theory, the odyssey battery should be able to handle that, but my resting
>voltage this morning was at 11.8. This does not even include lights, stereo
>or my Atwood furnace that I need to run. I'm thinking I probably now need a
>100AH or better auxiliary battery.
>
>So, looking for some options here:
>
>1:) I can simply flip a switch that I have installed and link together my
>starting battery and reserve battery. The danger of courses is running the
>starting battery down too much and being stranded.
>
>2:) install a second battery and link it to the odyssey under the rear
>bench seat
>
>3:) Buy a whole new 100AH capacity battery and install it under the rear
>seat and eliminate the odyssey or use it as a starting battery.
>
>Since all my wiring is now behind the rear driver's seat, I'd like to do
>this as painless as possible.
>
>So, suggestions for a good battery to buy, whether it be a simple flooded
>style that would not be deeply discharged or go with one of the expensive
>optimas or other AGM's. I'm located in Alaska, so shipping is a
>consideration as well.
>
>I think I've heard more than one person using a standard flooded battery
>with good success, purchased at Sears or Wally world for quick exchange if
>needed.
>
>I need to get something done quickly here, so any help would be
>appreciated.
>
>While I love this new refrigerator, it has definitely caused share of
>problems with battery usage!
>
>Cheers,
>
>Troy