How long would a 12v coolbox take to drain a battery?
Discussion
i have a 12v coolbox with inbuilt fan that i want to leave in the car running via the 12v socket when the cars off. It has my lunch for work in it, so would be in a turned off car for about 4 hours. i would turn it off after ive taken my lunch out.
the car is a 2011 golf tdi bluemotion and i assume the battery is good.
the cool box is 12v rated as 50w when plugged into a 12v dc source. not sure what sort of amps its pulling though?
car is left for a max of 8 hours from parking up in the morning to going home.
the car is a 2011 golf tdi bluemotion and i assume the battery is good.
the cool box is 12v rated as 50w when plugged into a 12v dc source. not sure what sort of amps its pulling though?
car is left for a max of 8 hours from parking up in the morning to going home.
A=W/V so 50 watts at 12 volts = 4.1666 amps.
Don't know the AH of your car battery, assuming it's 75AH it would equal around 18 hours to fully flatten the battery, although of course it wouldn't be able to fully use all of the battery's capacity, and draining it completely would mean you wouldn't be able to start the car.
I'm not sure how long you'd have before you were unable to start the car, but it's never a good idea to flatten and recharge an engine start battery, it's not what they're designed for. You need a leisure battery for that.
Don't know the AH of your car battery, assuming it's 75AH it would equal around 18 hours to fully flatten the battery, although of course it wouldn't be able to fully use all of the battery's capacity, and draining it completely would mean you wouldn't be able to start the car.
I'm not sure how long you'd have before you were unable to start the car, but it's never a good idea to flatten and recharge an engine start battery, it's not what they're designed for. You need a leisure battery for that.
Depends enormously on the condition of your battery. If you are going to run that type of accessory it's best to have a second battery and a charging system which deals with your primary battery first. These things are routinely available for caravans, camper vans, boats etc.
http://caravanchronicles.com/guides/understanding-...
http://caravanchronicles.com/guides/understanding-...
I think the easiest thing may be to try it at the weekend and see if the car still works afterwards. Possibly buy jump leads first. If you bung a couple of ice blocks in the freezer box each morning it may reduce the load on the battery. I'm not sure if those boxes have thermostats. I imagine that the results you get will be very different on a freezing day from a July heatwave day. It probably also depends on the size of the coolbox as space heating takes up different amounts of energy depending on the size of the space.
Don't do it!
Tried doing the same thing. O.K. it was some years ago but it was a new car and I tried leaving it for 8 hrs , not a good idea, battery was as flat as a fart.
You would probably need to go the leisure battery route if you really need to but freezer blocks would probably be the safer more reliable route.
Tried doing the same thing. O.K. it was some years ago but it was a new car and I tried leaving it for 8 hrs , not a good idea, battery was as flat as a fart.
You would probably need to go the leisure battery route if you really need to but freezer blocks would probably be the safer more reliable route.
Unless you wish to eat a specified amount of ice for lunch then freezer blocks will cope just fine in an unopened coolbox for four hours at keeping your meal fresh. A while ago I used mine to keep a bottle Champagne very drinkable over the course of two nights storage without resorting to plugging the thing in.
Impasse said:
Unless you wish to eat a specified amount of ice for lunch then freezer blocks will cope just fine in an unopened coolbox for four hours at keeping your meal fresh. A while ago I used mine to keep a bottle Champagne very drinkable over the course of two nights storage without resorting to plugging the thing in.
This, if you can't cope with having a warm lunch.Superhoop said:
Can you not get one with a cigar lighter adapter and a mains lead and then when you get to work just plug it in there?
im a mobile engineer so dont have a office to keep it plugged in at, thats the whole reason i have the coolbox, it tends to go a bit sweaty in the heat. will try it at a weeknend and see
4amp drain on a standard lead acid even at 60ah is going to be a fair drop in usable capacity, you wouldn't want to drop below 50% charge to avoid permenent reduction to the batteries storage, and that's after you've managed to start the car...
It may be okay, but I wouldn't want to risk it without an auxiliary leisure battery setup or similar.
It may be okay, but I wouldn't want to risk it without an auxiliary leisure battery setup or similar.
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