Caravan fridge power when tow vehicle turned off

Submitted: Monday, Jun 14, 2010 at 13:36
ThreadID: 79326 Views:3005 Replies:2 FollowUps:6
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Is it possible for caravan fridge to switch automatically from towing vehicle's source of power ie alternator, to the caravan's source of power when tow vehicle is turned off without manually switching the 12v system on in the caravan?

I asked for this system and have had this system previously but have been told by our new caravan supplier that this system is illegal. I don't want to have to remember each time to switch each time I turn off the the vehicle.

Thanks for information.
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Reply By: Notso - Monday, Jun 14, 2010 at 14:06

Monday, Jun 14, 2010 at 14:06
That's how mine works, all I have is a Redarc battery Isolator that shuts the power off to the van when the main battery drops below about 12.5 volts.

Having said this I don't use the 12 volt much in the van unless it's stinking hot and we plan to be on the road for a long time.
AnswerID: 420759

Follow Up By: Olive- Monday, Jun 14, 2010 at 14:22

Monday, Jun 14, 2010 at 14:22
Thanks for that. I will look up redarc isolators.
FollowupID: 690952

Follow Up By: hazo - Monday, Jun 14, 2010 at 15:34

Monday, Jun 14, 2010 at 15:34
Running the fridge (assuming it is a 3-way) directly from the caravan battery will quickly flatten it ! most 3-way fridges take around 14A when on 12vdc.

There is a fridge motion switch, available, that detects if the vehicle is moving and isolates it from the car (battery) to stop it flattening that.
A Redarc will do the same job but probably more expensive as they are designed for dual battery systems in vehicles.

If stopped for any length of time it is far better to switch over to run from gas, or obviously 240vac if available. but if stopped for just a tea break or lunch just leave the fridge off for that short period.
FollowupID: 690958

Follow Up By: Member - DAZA (QLD) - Monday, Jun 14, 2010 at 16:42

Monday, Jun 14, 2010 at 16:42
Before we start towing I switch the the power source over from 240 volt to 12 volt, this is supplied by the batteries in the van, I also help charge them with the Anderson Plug from the tow vehicle, which is connected to the Auxilary Battery in the 4by, the starting battery is isolated, this will change when I get the Solar installed, when we get to a powered site it goes back to 240volt.
FollowupID: 690966

Follow Up By: Ray - Monday, Jun 14, 2010 at 17:54

Monday, Jun 14, 2010 at 17:54
With the situation that I have I have 150amphr batteries in my caravan. The 3way fridge is powered from these batteries WHEN the engine is running but is isolated when the engine is turned off. These batteries are charged via an Anderson from the cars alternator whilst travelling. I only use this system on long runs. For other times I rely on the isolation of the fridge to keep it cool. You can buy a relay that will isolate 12v from 240 but where I do not know.
FollowupID: 690983

Follow Up By: Olive- Tuesday, Jun 15, 2010 at 15:21

Tuesday, Jun 15, 2010 at 15:21
Thanks for this information. Will look at all suggestions.
FollowupID: 691108

Reply By: drivesafe - Monday, Jun 14, 2010 at 19:18

Monday, Jun 14, 2010 at 19:18
Hi Olive, what brand and model of fridge do you have.

If it’s a newer Dometic three way fridge, it will most likely have AES ( Automatic Energy Select ) which if wired up in your new van then the fridge will automatically switch switch the 12v supply off when the ignition is turned off and switch to gas approximately 20 minutes after.

If your set up any other way, particularly to use power from your house battery, as hazo pointed out, this is really a No No. It will shorten the operating life of your house battery if used to supply such high current loads.

But first, again, what fridge do you have and then options can be suggested.
AnswerID: 420799

Follow Up By: Olive- Tuesday, Jun 15, 2010 at 15:15

Tuesday, Jun 15, 2010 at 15:15
It is a Vitrifrigo 2-way fridge.
FollowupID: 691104

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