How long would a 12v coolbox take to drain a battery?

How long would a 12v coolbox take to drain a battery?

Author
Discussion

okie592

Original Poster:

2,711 posts

145 months

Sunday 27th July 2014
quotequote all
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.

Ledaig

1,616 posts

240 months

Sunday 27th July 2014
quotequote all
It's 4.2A, just back work from your batteries capacity for the drain.

A better question would be "how much charge do I need in my battery to start my car" wink

juliethotel

253 posts

127 months

Sunday 27th July 2014
quotequote all
amps is watts divided by voltage so:

50 divided by 12 is just over 4.

4 and a bit Amps

I'm going to take a wild guess and say your battery is about 60AH (amp hours)

I think this means It can sustain 60 amps for an hour.

So basically I think you'll be fine.

(this may be totally incorrect)

zed4

7,247 posts

200 months

Sunday 27th July 2014
quotequote all
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.

Qwert1e

545 posts

96 months

Sunday 27th July 2014
quotequote all
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-...




jsp56

152 posts

95 months

Sunday 27th July 2014
quotequote all
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.

evoivboy

871 posts

124 months

Sunday 27th July 2014
quotequote all
we left our 2004 Audi A6 plugged in to one for 4 hours and it would not start

Dunc B

196 posts

251 months

Sunday 27th July 2014
quotequote all
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.

Impasse

15,099 posts

219 months

Sunday 27th July 2014
quotequote all
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.

Superhoop

4,621 posts

171 months

Sunday 27th July 2014
quotequote all
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?

Krikkit

23,925 posts

159 months

Sunday 27th July 2014
quotequote all
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.

Divvyboy

450 posts

96 months

Sunday 27th July 2014
quotequote all
Also a potential for fire if the cool box malfunctions.i would not do it

Nickyboy

6,465 posts

212 months

Sunday 27th July 2014
quotequote all
If the box is cold when you leave it then it should keep the lunch cold easily enough without the need to keep it running. My old standard coldbox would keep things cold with icepacks for close to 10 hours.

okie592

Original Poster:

2,711 posts

145 months

Sunday 27th July 2014
quotequote all
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

mclwanB

510 posts

223 months

Sunday 27th July 2014
quotequote all
As an ambulatory vet I have one in the car. Even with a high capacity battery and a circuit that senses low charge 24hrs ok more not!

ali_kat

31,854 posts

199 months

Sunday 27th July 2014
quotequote all
ears

Similar problem, only I'm away all week with no access to a fridge or freezer

Hooli

32,278 posts

178 months

Sunday 27th July 2014
quotequote all
Do the fag lighter sockets in your car work with the engine off OP? I can't think of any modern cars I've been in where they do.

cuprabob

11,221 posts

192 months

Sunday 27th July 2014
quotequote all
As above, on the later.VWs the.12V socket in the car and the.boor.only work with the ignition on.

okie592

Original Poster:

2,711 posts

145 months

Sunday 27th July 2014
quotequote all
cuprabob said:
As above, on the later.VWs the.12V socket in the car and the.boor.only work with the ignition on.
linked out to provide a permanent live

PhillipM

6,016 posts

167 months

Sunday 27th July 2014
quotequote all
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.