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I have a car with a second 12v electric point. If I were to use it to run an electronic cool box or charging my light, how long will my car battery last?
Depends on the draw of the cool box and the ampere hour of the battery.
Both of them will have it written on them.
Charging your bike lights - it'll last forever. Coolbox will be a relatively big drain. As its summer your in luck as the cranking current that the battery can provide will be high so you've got a good chance that the car will still start.
Thanks.
Small items in our camper are fine phone chargers battery chargers ect. The fridge comes off the driving battery or off the hookup. If we ran it on the leisure battery it would last 6 hours max, then the battery would be not just flat but damaged. If we cool it down while driving it usually lasts a while.
If you want to run a coolbox and you only have a single battery it would be advisable to fit the inline battery monitor [url= http://e.dominohosting.biz/dca/mpsdb01.nsf/Refrigeration01!OpenView&RestrictToCategory=ENGEL%20ACCESSORIES ]linky[/url] This will shutdown power to your coolbox whilst retaining enough power for you to restart the engine - it could save having to push start the vehicle.
Cool boxes are quite a high current drain, around 4amps, I think.
A split charge system is best to avoid a flat battery.
If it's only for one day though, a spare battery charged up at home before you leave is easier.
Mate of mine ran a cool box and car radio for two days at a festival recently, when he came to leave his battery was flatter than Keira Knightley. Depends on the car / battery obviously, but I'd take a pair of jump leads. (-:
I did some calcs a while ago, and a cool box will easily drain a car battery if you leave it on overnight. Best bet is to buy a big Igloo Maxcold box and stick a load of ice packs in it - they'll stay cool for a few days quite happily.
What tron says. I did a trip in the Australian outback 20 years ago with a an old top loading freezer packed with ice to keep the meat cold. Worked for 2 or 3 days when it had to. Change of state requires loads of energy.
a top of the range 12 volt fridge drains 20 amps per day a cool box 4-6 amps. You have probably 60-100 in your battery* [fiesta to big diesel as scale]. You need huge cranking amps to start so any voltage drop will be poor for you car at start up. So roughly 5 hours and youcan probably still start the car.I would fit a second battery with split charger personally or ice packs in cooler etc
If you are drivin git is fine to use as the alternator will respond to the additional load and will not flatten the battery.Dont run engine to charge battery as it is really ineffiecient /almost useless as a charger
* It is considered flat when 50% of them are used[to prevent damage to battery as it is not a traction battery you are using] and may start your car but it will struggle.
Our caravan battery will flatten very quickly on 12v, its basically for running while the car is connected as its getting a 12v feed from the split charge when the cars output is high enough. To be honest it doesnt work that well on 12v anyway. Far better solution is to stick a frozen 2 ltr bottle of water in there. That will keep the fridge cold for a good no of hours. Same with cool-boxes. Remember camping in Dorset a few years ago, chap had a cool-box that was supposed to cut-off when the cars battery ran low. Needless to say it didnt, & the AA had to come out.