Troopie replied:

Wow - lotta questions. Without getting into the complexities, here are some shoot-from-the-hip answers:
1. Fridges will run happily in most vehicles while the motor is running (the "day trips" you mentioned.
2. Fridge running without a second battery - depends! Battery, current draw of fridge, ambient temp etc etc - my preference would be not to to risk it. Having said that, I suspect that a spece for a second battery will be difficult in a sedan - there is a brand of battery (I have forgotten it's name - anyone?) that is basically two batteries built into the one case - it even has seperate terminals for accessories.
3. Direct cable is the way to go - the goal is to minimise voltage loss (i'm no expert here though).
4. It's best to leave at least a small amount of space around the fridge - but it's most important to leave space around the vents for the motor/compressor.
5. Heat given off is minimal, but noticable on some models.
6. Noise is not much of a problem, I have not seen one than can be heard much above average road noise. I actually don't mind hearing the fridge cut in and out from time to time - reassuring to know it's still going!
7. Handling the gravel roads shouldn't be much of a problem - as long as you buy a decent fridge (not entering that debate) and look after it. My fridge has copped several years of rough trips as well as acting as an extra fridge at home and it hasn't missed a beat.
8. Not sure about the most economical 2nd battery set-up - I actually have three batteries under the bonnet of my troopie so economy went out the window some time back. There is a device called a "power tank" which is basically a battery pack that charges from the 12 volt socket in the car - one of these may serve your purposes.

That about does it in summary form - all of what I said is subject to debate though!

Cheers

Member - Peter replied:

see waco.com.au (remote power systems ) I have the unit called the URBIN it has a 24 amp hour charge ,a fast charge unit is also avalible with it, that should charge the battery in approx 2-3 hours when engine is running. A waeco cf50 fride freezer running at the second setting ( 2 lights ) willdraw approx 1-2 amps so you are at least going to get 12hrs running time before a recharge is required. this same fridge has a auto cut of ,so if you are running it of your main battery it will not fully flatten it . The remote power packs are a dry cell battery so are quite same to gharge inside your car .Hope this is of help Peter York 4x4