16' Series 3 way fridge on 12v

[MarkAW]

Hi
How does everyone elses fridge go on 12v?
We spent the weekend camping in the 40 degree heat running the fridge in our 2017 16.49.4 on gas. As always worked brilliantly and kept the temp between 0 in the morning and 4 degrees in the afternoon with the sun shining on the fridge side of the van.
On the 3 hour drive home in the heat (about 40 degrees) the temperature in the fridge went up to 9 degrees.
It is wired as per Jayco recommendations through the 12 pin plug and runs off the 2nd battery. (used the biggest gauge wire that fit into the larger 12 pin plug). The 12 pin plug felt hot when we got home.
I'm thinking of running a dedicated anderson plug from the battery to the fridge.
How do others find the 3 way fridge running on 12v?

 

[Drover]

12v is not all that great especially if the fridge isn't full, ours does the same when its stinking hot and not s lot of stuff inside it....Go the Anderson, no chance of a plug melt down.

 

[TimS]

Had the same issue, the 12 pin plugs should handle the current draw but in reality they don't.
Changed to an Anderson plug, problem not totally solved but the fridge now will keep a reasonable temp when driving.
I think heavier wire from the car battery to the fridge may help.

 

[Drover]

You really need a dedicated run from the tug battery, 8B&S cable is a good size.

 

[Boots in Action]

Hi
How does everyone elses fridge go on 12v?
We spent the weekend camping in the 40 degree heat running the fridge in our 2017 16.49.4 on gas. As always worked brilliantly and kept the temp between 0 in the morning and 4 degrees in the afternoon with the sun shining on the fridge side of the van.
On the 3 hour drive home in the heat (about 40 degrees) the temperature in the fridge went up to 9 degrees.
It is wired as per Jayco recommendations through the 12 pin plug and runs off the 2nd battery. (used the biggest gauge wire that fit into the larger 12 pin plug). The 12 pin plug felt hot when we got home.
I'm thinking of running a dedicated anderson plug from the battery to the fridge.
How do others find the 3 way fridge running on 12v?

Hi @MarkAW , the real problem is usually the voltage output from the alternator. Modern tugs improve fuel consumption by cutting down voltage (and isolating the alternator altogether) when the electronics senses that the TUG battery is fully charged. It may start at 14.4 volts, but drops back to 13.2 volts or so when it can. It does not recognise the fridge as a load. Although the fridge is rated at a nominal 12 volts, it really works much better at higher voltages (up to nearly 16 volts) which allows more current to heat element and better cooling. If you are travelling along with a lot of accessories on in the car, that will pull down the voltage available to the fridge. In fact, if travelling at night or stopped at lights with or without indicators on, battery voltage could be near only 12 volts even with alternator working. That is why van batteries can never be fully charged by using alternator, no matter how long you run the car.

@Drover has posted a great explanation on battery charging and what happens when connected to car. Different brands and models will vary, but there is a modification to alternator that will recognise the fridge as a load and so keep the alternator charging at the higher tug voltage. Otherwise, a DC to DC charger is the the only way. I will see if I can find it again and send it on to you.

 

[MarkAW]

Thanks Boots
Finally had a chance to check the voltage on the wire from second battery to 12 pin plug. Battery and plug both 12.85v
Hooked up the caravan and checked the voltage at the back of the fridge in the bottom vent, also 12.85v
However when I turned the fridge on the voltage under load dropped to 10.70v. This drop seems excessive.
The cable I have used is the below from Jaycar

Ideal for just about any low-voltage high-current application. Rated at around 100A, but we’d suggest around 90A or voltage drop may become an issue.

Features:
- Tinned Copper Conductor
- Red / Black Figure-8
- High Current

Specifications:
• Rated Current: 90A
• Stranding: (7 x 7 x 24 x 0.12mmTC) x 2
• Conductor diameter: 4.11mm x 2
• Insulation: PVC
• Conductor mm2: 13.3mm2 x 2
• AWG: 6
• 50 metre roll or sold by the metre
• Dimensions: 8.5mm x 17.0mm