So it now time for me to get down to the
2nd battery install that has been waiting for me

I was thinking what I would like was the full monty but at $ stores prices
What I want
-AC charge system
-seamless ac/dc supply from the 2nd battery *OR* the external ac supply
-battery discharge regulator so that current is stopped if the 2nd battery
is at less that
   some percentage (say 50%) as measured by voltage, to protect the deep
cycle
   battery from large dischrage conditions that tend to shorten any battery
life

So it seems the ideal magic box would would be both a converter to take the
external ac & send it to either ac or dc circuits and it would also do the
reverse
take the dc from the 2nd battery & send it to either ac or dc circuits at
the same time.
This way the standard vanagon ac outlet would work any time & same with the
devices on the dc circuits (light, stereo, cig lighter)..

It would also act as regulator to stop draw on the battery of it was to
discharged
to protect the battery life

I could also use the external ac supply to trickle charge the 2nd battery

I would also want to add a solar charge system later to trickle charge
during outback camping

I think this is the type of device to handle these demands
xantrex call it an inverter / charger
http://www.xantrex.com/web/id/49/p/1/pt/8/product.asp
but it is over 3000 watts I dont need that much  power / price

I am open to any solution with attention to price/function :)