How to use / advice for 12v Coolbox and battery implications ?

[Grobynet]

Have Touring Sports 2.0 Design and am ignorant on the does and donts of when/when not to have a 12v coolbox plugged in / switched on in the boot, to ensure I avoid any Battery problems for starting etc.

Any advice / tips / guidance would be appreciated - like for example if you leave it in parked car for several hours / day and forget to unplug, what is the impact / risk ?

thank you

[Rosgoe]

Pretty sure the power is disconnected to the 12v accessory socket once the car is turned off the car will shut the power down anyway after 20 minutes on the hybrids in accessory mode so as not to drain the 12 volt Battery.

[TonyHSD]

Hi, only use when car is in Ready mode or while travelling otherwise you will risk to drain the 12v Battery. 

[Gerg]

There seems to be a convention that Japanese cars switch off their 12v 'accessory' sockets when the ignition is switched off, and German cars and their derivatives (and Ford it seems) leave their sockets permanently live.  Perhaps someone knows a complete list or rule of thumb?

Your typical Halfords-style coolbox probably pulls a bit less than 4 amps in normal use, so your 55 amp hour 12 volt battery could run it for 55/4 hours, so around 13 hours.  But the Battery would then be completely flat and the car would not start, so best not to go beyond half that time...

But, as mentioned in posts above, the car, in standard form at least, will not allow the coolbox to be left on with the car off.  So you have nothing to worry about, apart from your food and drinks not being cooled when you leave the car unattended.

But get into a German car or similar and the above maths do apply, assuming the Battery is 100% functioning and charged, and 55 amp hours in size.  For maximum Battery life it is best not to drop below 80% of full charge, if you can avoid it, say the battery manufacturers.  So that would give you around 3 hours use in your hypothetical VW or Ford etc., before you start to wear out the 12v battery a little more.  For AGM technology batteries, this last suggestion is less of an issue - they are built to take deeper discharges without so much wear taking place.

Hope that helps.

[Rosgoe]

4 hours ago, Rosgoe said:

Pretty sure the power is disconnected to the 12v accessory socket once the car is turned off the car will shut the power down anyway after 20 minutes on the hybrids in accessory mode so as not to drain the 12 volt battery.

You could always use a separate 12 volt power supply carried in the boot when the car is off such as one of those jump starters power packs with a 12 volt output socket then re charge when you get home.

[Rhymes with Paris]

I found it helps to use the freezer blocks as are used in non plug in coolboxes ,4 of them 2 either end.

This way it keeps your stuff cool when switched off ,and extends the frozen Life of them when switched on.

I have run a box for 8 hours with engine off in a deisel with a 70 a/h Battery no problems , conversely the same box drained a 60 a/h Battery in a is 200 Lexus in 3 Hours (new battery)

So to be sure I switch on only with engine running.