Sounds almost too easy.  You can get a 6VDC to 120VAC converter if you look
really hard in the JCW catalog or bug the dickens out of your local ancient
rv folks.  Then it's a simple matter of hooking your 120vac battery charger
and running to the battery set.  

To charge the "12VDC" battery you'll need 13.8VDC+ a little which of course
you can't easily get from 6VDC.  Kinda like making a waterfall run backwards.

Sacrilegious to convert the bus.  Maybe a solar charger for the long days at
the beach.  

Basics of conversion to 120VAC from DC.  Use a "chopper" to break the DC into
pulses at 60 hz (cycles/sec).  Use a transformer to go from 6vdc chopped to
130VAC.  Filter the trash off the 130VAC 60~ to get 115VAC nominal.

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         ___  / __   __/   ____/         Al Knoll HP Performance Technology /
        /    /      /     /             Center    Roseville, CA, USA 95747 /
       _____/      /     /             916.785.5317    (Telnet 785-5317)  /
      /           /     /             email:  alf@hpptc44.rose.hp.com    /
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