jimmi:
ive got a 12v cooler from halfords and it stays on all week and never affects the starting power in a morning. it does go off on a weeknd tho
no probs on my Scania either! 
triple-tango:
shuttlespanker:
i have got a 24v coolbox in one of my MAN’s, can leave it plugged in overnight no problems, but not over a weekend+1
+2 60 plate man
Got a factory fitter fridge/freezer in my actros.
When I’m on nights out I have the TV on for 4-5 hours, and fridge running all the time.
Even at weekend I don’t turn fridge off. Never had a problem starting.
But I think it knocks off if it’s been stood for so long.
But my fridge doesn’t seen to get as cold as it used to.
I think the cab tilt mechanism switch is sticking and have to bang the fridge shut sometime to get it to work. Used to freeze water if it was turned up full.
I’ve got a cheap £35 one from Aldi. Box is 3 years old. I plug it in on a monday morning and unplug it on friday night or saturday morning depending when I finish. I have done this since I had the box. My current Scania is 18 months old and I have never had a problem with the batteries.
I do run the engine for 5-10 minutes before going to bed if I have been parked up for a few hours.
Got the same one from Aldi and used to run it monday to friday non stop without any battery problems, although i turn it off overnight now because i cant get a good nights sleep with it running
I have a Coleman 12v cooler, it about the biggest 12v one you can buy, I leave it plugged in all week but if I know I will not be running the engine for more than 12 hours then I would unplug it. I have only once flattened the battery but it was plugged in for 16 hours and I had the TV /DVD player running also. If i know I ma going to leave it for a very long time I make sure I do not open it so it keeps the drinks and food cool.
I have got a Waeco CF 50 Dual zone fridge freezer for sale of you want a proper one! Used to leave it on all week and plug it in the mains at the weekend.
i leave mine on all week … but then i have a leisure battery 
Doesn’t anyone lug a couple of car batteries in the passenger footwell for running such DC thirsty appliances? 
When I was tramping I always started the week with a couple of frozen ice packs in the cool box and they would help to keep the box chilled even when unplugged overnight, I always unplugged it as I wanted to watch TV for a couple of hours and didn’t want to get caught with a flattery! (I did just once when cool box was left plugged in and I watched TV for 3 hours too… 
Later I had a leisure/slave 12v battery that only charged when the truck batteries were fully charged, then I left the cool box on 24/7, it just stopped when the slave went flat but kicked back in within a few minutes in the morning.
I used to keep milk, yoghurts, bacon etc in the box all week with no problems…
Grayham:
Got the same one from Aldi and used to run it monday to friday non stop without any battery problems, although i turn it off overnight now because i cant get a good nights sleep with it running
Park next to a reefer box then 
bowserman:
I have got a Waeco CF 50 Dual zone fridge freezer for sale of you want a proper one! Used to leave it on all week and plug it in the mains at the weekend.
How much bowser■■?
A good tip to remember is to always keep the fridge well stocked as it works better. Mine is usually full of fresh at the start of the week then as it gets depleted I put bottles of water in or a few tins of peach slices/fruit cocktail etc in to take up some room. Another way to help it is after having a shower, lay the wet towel on top of the fridge to dry out.
When I were a tramper, I had a weaco 45 which I kept at freezer temp, frozen foods, Ice lollies and Ice creams all day, I also kept a couple of Ice packs in it and kept salads, drinks and fresh foods in a coolbox, just swap ice packs twice aday with the ones in the freezer and jobs a goodun. 
Grayham:
although i turn it off overnight now because i cant get a good nights sleep with it running
I have a cheap Halfords cool box that I used to leave on overnight, but struggled to get a good sleep. I was overnighting on an RAF base in Wales and decided to put the cooler outside - still plugged in - under the front footwell in case it rained.I was awakened by blue flashing lights at 2am - RAF police had seen a box with wire attached under a lorry and went into alarm mode! I had one of the biggest bollickings I’ve ever had there and then
Oh - and a cat had ■■■■■■ on the cool box, took me a week to get rid of the smell 