12v Power 2016 Polo 81tsi

**loj94jdn** · 10-06-2017, 12:02 PM

Hi all - any ideas what the max rated current is for 12v power outlet as standard? I have a need to travel a long distance with a large camp fridge and not sure if I need to get the wiring upgraded or if it will do the trick. I think it's a 20a fuse but that doesn't by default mean it supports sustained hire current draw!
Will only be in car when it's running and will be powered from 240v overnight.
Max draw of fridge is 4.5a
Tia!

**extermin8tor** · 10-06-2017, 03:47 PM

As a ballpark I would say it should handle a maximum of 10A which at 12 volts is about 120W.
My 45L Chescold fridge was rated exactly for that (120W) - most car 12V fridges are typically rated for the maximum that the outlet can handle (120W).

I will just say that it is likely that the manufactuarer probably used the cheapest wiring possible so at the maximum load (10A) it will likely get slightly warm and increase its resistance, this reducing power.

Either way, just give it a go, if its not tripping fuses and you don't get any burning smell it should be fine.
I would be more worried about your battery being drained if you have any auxilary stuff.

My Nissan X-Trail had a rear 120W 12V socket and handled it fine, the wiring that came the fridge was obviously crap because it got warm.

Your mileage may vary. Good luck!

**DV52** · 10-06-2017, 04:34 PM

loj94jdn: Some very good questions indeed. First thing to appreciate is that 12V car fuses really aren't intended as overload protection devices - they are much better at fault protection (which is an entirely different thing)! Also, whilst the written number on the body of a fuse is important, it's a nominal rating only.

The old rule-of-thumb used to be that it is unwise to operate a circuit with a fuse of a certain rating if the current flow was above 75% of that rating.

Just because a fuse has the number "20" (say) doesn't mean that the fuse will blow @20 Amps. What happens is that the current-sensitive material in the fuse starts to melt at a much lower current - so it really depends on the time characteristics of the overload/fault as to what actual current the fuse element opens the downstream circuit. For example - it would not be unusual for a 20 Amp fuse to open @ 40 Amps - if the profile of the fault was characteristic.

If your ice-box has a 4.5 Amp compressor- then it will draw 63 Watts @ a nominal 14 Volt (which will likely be the general rail voltage with the engine running) - when chilling. A circuit with a 20 Amp fuse should easily be able to manage this load.

Don

**Hillbilly** · 10-06-2017, 04:47 PM

Just as a for instance, Waeco provide a power unit for fridges and the wiring in that is 6mm automotive. Which is 4.8mm sq and is much heavier than what is in a normal car ciggy circuit.

I would never try to run a car fridge off a ciggy outlet as the wiring is a bit like thick cotton and the voltage drop from front to rear would be fairly high as well I would think. Have seen car wiring insulation melted by doing this when the wiring overheated due to being asked to do more that it was designed to do.

**Transporter** · 10-06-2017, 08:52 PM

Originally Posted by loj94jdn

Hi all - any ideas what the max rated current is for 12v power outlet as standard? I have a need to travel a long distance with a large camp fridge and not sure if I need to get the wiring upgraded or if it will do the trick. I think it's a 20a fuse but that doesn't by default mean it supports sustained hire current draw!
Will only be in car when it's running and will be powered from 240v overnight.
Max draw of fridge is 4.5ax
Tia!

If it's 4.5A max. You should be ok, then.

**Hillbilly** · 10-06-2017, 09:07 PM

What is the brand and model of the fridge

**loj94jdn** · 14-06-2017, 11:51 AM

Originally Posted by Hillbilly

What is the brand and model of the fridge

Im looking at the Engel 85L (newest one)

**loj94jdn** · 14-06-2017, 11:52 AM

Originally Posted by DV52

loj94jdn: Some very good questions indeed. First thing to appreciate is that 12V car fuses really aren't intended as overload protection devices - they are much better at fault protection (which is an entirely different thing)! Also, whilst the written number on the body of a fuse is important, it's a nominal rating only.

The old rule-of-thumb used to be that it is unwise to operate a circuit with a fuse of a certain rating if the current flow was above 75% of that rating.

Just because a fuse has the number "20" (say) doesn't mean that the fuse will blow @20 Amps. What happens is that the current-sensitive material in the fuse starts to melt at a much lower current - so it really depends on the time characteristics of the overload/fault as to what actual current the fuse element opens the downstream circuit. For example - it would not be unusual for a 20 Amp fuse to open @ 40 Amps - if the profile of the fault was characteristic.

If your ice-box has a 4.5 Amp compressor- then it will draw 63 Watts @ a nominal 14 Volt (which will likely be the general rail voltage with the engine running) - when chilling. A circuit with a 20 Amp fuse should easily be able to manage this load.

Don

Good man - very comprehensive info - much appreciated

**Hillbilly** · 14-06-2017, 12:38 PM

Originally Posted by loj94jdn

Im looking at the Engel 85L (newest one)

Well I would use 6mm automotive as a minimum to power it Much safer than running it on a bit of cotton as usually used in ciggy circuits.

If Waeco use that for smaller fridges that is as good a recommendation as you can get

**loj94jdn** · 14-06-2017, 01:51 PM

Originally Posted by Hillbilly

Well I would use 6mm automotive as a minimum to power it Much safer than running it on a bit of cotton as usually used in ciggy circuits.

If Waeco use that for smaller fridges that is as good a recommendation as you can get

So youre suggesting to direct wire it or use 6mm cable from ciggy lighter to fridge?