I am running the 30 amp SmartCharger from Astron:
http://www.astroncorp.com/smart.shtml

It is extremely lightweight, about 4 pounds. Forced-air thermostatically
controlled cooling. Switched-mode conversion for any voltage input, and no
buzzing transformers.
It fits under the driver's seat nicely along with an inverter and 2 relays
that switch the system on/off when plugged in, so I don't need to reboot my
computer when on battery/inverter.  Also an advantage is that when on plugin
the inverter is off completely. It's a great system.

--  Rachel
http://www.Gnarlodious.com/Vanagon/Vanagon.html