12v on Fridge Query

[Paul542]

Hi I have noticed the 12v switch on my fridge does not illuminate and no power to it when on electric hookup and battery.

Does this 12v only work when it's connected to the car tow bar?

Thanks

 

[RogerL]

Yes

 

[Raywood]

The power needed by the fridge on battery is such that it would drain the battery very quickly and so is only available when the car engine is running and can recharge the battery. Even then this will only maintain the lower temperature in a cooled fridge and should not cool down one from room temperature.

 

[Damian]

Even then this will only maintain the lower temperature in a cooled fridge and should not cool down one from room temperature.

Actually it will cool down a fridge from room temp if, and it is a big IF, the car travels for long enough, which the majority do not.
It would take about 4 hours continuous power feed to achieve this.

 

[xtrailman]

My fridge has the same 170watt element for cooling for mains and 12volt ( one for each ).
So in theory should perform the same.

Problem with the 12volt system is providing 12volts to the fridge at all times, along with keeping the fridge level enough while towing.

 

[ProfJohnL]

Hi I have noticed the 12v switch on my fridge does not illuminate and no power to it when on electric hookup and battery.

Does this 12v only work when it's connected to the car tow bar?

Thanks

That will depend on the make of fridge and how its been wired into your caravan. but as others have pointed out the fridges 12V cooling operation is only available when the tow car is producing enough power during a journey.

 

[Buckman]

What about cars with Smart alternators which I am led to believe probably will not even keep a fridge cool on a long trip? Can you have a dedicated 12c connection for the fridge and where is it generally sorced from or does it differ on very car? TBH I have never use the facility on the Jeep as have no idea if it will keep the fridge cool.

 

[RogerL]

What about cars with Smart alternators which I am led to believe probably will not even keep a fridge cool on a long trip? Can you have a dedicated 12c connection for the fridge and where is it generally sorced from or does it differ on very car? TBH I have never use the facility on the Jeep as have no idea if it will keep the fridge cool.

Cars with Smart alternators are fine - IF - they're wired correctly - it's cars with smart alternators wired with smart relays that are the problem as smart relays aren't smart enough to handle the variable voltage from the alternator.

Wiring needs to go back to old-fashioned principles - take a fused feed direct from the car battery and use a relay trigged by ignition on - avoid cheap voltage sensitive relays.

 

[xtrailman]

It does vary from car to car.

When towing my car often gives out 14.7 be volts when it arrives at the fridge anything over 14.3 v gives 12v at the fridge.

Even then the fridge temperature increases after 2 hours depending on ambient temperature.

I monitor both temperature and voltage while towing.

And I have increased the caravan wiring from 4 to 10mm.

 

[ProfJohnL]

There are several web sites and threads about how to arrange to use a smart alternator to charge a leisure battery ( often for camper vans,) and to incorporate solar or wind power as well. The solutions are not cheap (£250 upwards), but it is possible.

Another thought is the fridges often selected for camper van conversions are compressor driven, which is by far the most efficient cooling system, and using them can allow a fridge to be run on 12V only, and for solar panels and a storage battery to provide the bulk of the power to do it.

 

[Buckman]

TBH I have no idea if my car has a Smart relay or whatever for the frdige and I have no idea how to check?