My one from maplin is still in its packet, must try it soon, even if it wont start the car , at least It won't totally kill the battery. I'm not quite sure on the implications of totally flattening a battery on a modern car with all its electronics.
I bought a three way fridge after working out that a 907 Campinggaz cyl would last for about two weeks compared with
a similar sized car battery say 40Ah would only last about seven hours.
ie 40Ah*12V = 480 Watts for one hour.
Fridge takes about 65W so 480/65 = 7.3 Hours ,
and thats in theory ,never actually tried the practice with a new battery , though once flattened a clio's battery in a couple of hours with a cool box , very embarrassing.
I run a Engel MT35F Fridge/Freezer (set to operate as a fridge, not a freezer I might add) from a second battery (Exide Maxxima DC 900) fed from a split charge in my Discovery. Fully charged the battery will run the fridge for over four days without a further charge from the Disco.
I have fitted a caravan (12S) socket on the back of the disco that is hooked up to the second battery - when camped I carry the fridge into the tent (just so it's easier to get too then running back to the car when you need something) and use a trailing lead from the disco to provide the 12v electrics to the fridge and further sockets for phone charging etc...
Coolboxes will kill a vehicle battery. They draw a heck of a lot of power and in doing so, will warp the plates in your battery when you let it discharge too low.
The best plan is to run them on a hook-up with a voltage regulator - Cool Box Power
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Topic: powering cooler boxes via the car
