I recently posted a subject on how I could keep my coolbox working in my
Volkswagen campervan Pooh.

I have now, with many thanks to the many helpful replies via the group
and Email, worked out a neat way to keep my 12 volt coolbox from
draining the battery too much.

When parked up with an electric hook,  I plug in my battery charger into
the mains. This delivers 12 Volts up to 7 amps.

The battery charger is then connected to the heavy duty Positive and
Negative terminals of my powerpack.

The coolbox is finally connected to the cigar lighter output of the
powerpack.

The powerpack which I got from Argos (UK General Store)  delivers a 15
Amp Hour output via 2 cigar lighter sockets a switchable 4.5 v 6v and 9v
line socket and the two heavy duty 12 volt terminals

I tested this combination overnight and the battery charger kept both
the cool box running and the power pack fully charged.

For sites where there is no mains hook up, I will use a large leisure
battery that will be connected to the van alternator for charging while
on the move and disconnected when parked up.

I will eventually get round to permanently wiring the leisure battery up
with an isolation device to prevent the van's main battery from being
drained when parked up. I have a rough idea of what is required though I
do need to find a camping accessory shop or an electronics store to get
the parts. In the meantime its a  job of well insulated jump leads!

You can read about all the repairs to my 1981 Holdsworth Villa
Volkswagen Camper including pictures at
http://www.users.globalnet.co.uk/~mpages/

For a bit of light reading, also read 'Pooh's Diary' - its about the
adventures of a campervan that talks!