Refrigerator and inverter while traveling

[jamaddox]

I have a 2016 27dsrl that I would like to add an inverter to so I can run the refrigerator on while towing it. I am interested to know if anyone has done something similar what size inverter I would need? I just plan on using it for the refrigerator while towing so that my truck should keep the battery charged while towing it. I am not interested in the propane solution.

Speaking of recharging the battery from the truck I have an f250 with dual batteries but still wanted to confirm that using this would not drain my truck batteries too much. If anyone has any suggestions please let me know.

[Grumpy]

Depending on which fridge you have the current draw for the heating element could be between 1.5 to 3 amps. I think in order to be safe I would not go below a 750 watt inverter.

The big "if" on the truck keeping the battery up will depend on what size wire was used for the 12v supply back to the 7 pin.

[SloPoke]

I had tried this in our prior motorhome. We put an 800W inverter in the forward portion of the cab, to supply 120v power to the fridge.

The downside of this was that a typical AC/Propane Fridge draws 350W for the element. It makes the Inverter draw over 30A @12v to maintain the AC power just for the fridge. If you happened to stop along the way and forgot to switch the fridge off of inverter power, the battery was quickly discharged. After forgetting the second time - that was enough for us to leave it on Propane while travelling.

[CampNow]

Originally Posted by Grumpy

. . .

The big "if" on the truck keeping the battery up will depend on what size wire was used for the 12v supply back to the 7 pin.

Agree, a big "if"!

The 120 vac heating elements in the propane/electric frig are probably going to draw about 20-30 amps of 12 vdc via an inverter (amount varies with the size of the fridge). Best to go with at least a 600 watt inverter.

However, even if your truck had 10 batteries and a ~400 amp dual alternator, it's not going to prevent the trailer's batteries from eventually discharging with that kind of load.

The maximum current the truck's 7-pin connector can safely handle (continuously) is approx. 10-15 amps. The remaining current deficit is going to be supplied by the trailer's batteries. If the trailer's batteries run down too far (while connected to the truck) there's a chance you could overload the truck's 7-pin connector wiring as it tries to supply the full 20-30 amps of 12 vdc. Trucks typically use only 10-12 gauge wiring for the 7-pin connector---not heavy enough to be supplying 20-30 amps continuously over 20-25 ft. of wire (length of truck). If the fuse for the truck's 7-pin connector doesn't blow/open as designed, there is a chance you could start an electrical fire in your truck.

That's too many if's for me.

[jamaddox]

Thank you all for the information. It now looks like I have 4 options
1) use propane
2) I know the reefer can last 4-5 hours with a gallon of ice in it so I don’t travel longer than that per day
3) Buy a 12volt travel cooler(although those only cool 40degrees below ambient air). This might not work in the back of the truck bed
4) purchase a roto molded cooler and not open it up on the way
5) purchase any groceries at any stop on the way.

[nighthawk87]

I run with the propane on all the time. Seems to ruin the point of having a fridge if I can’t use it when traveling

[jamaddox]

Just kinda nervous still on running with propane. Makes me think of running with scissors

[Duke4857]

Originally Posted by Grumpy

Depending on which fridge you have the current draw for the heating element could be between 1.5 to 3 amps. I think in order to be safe I would not go below a 750 watt inverter.

The big "if" on the truck keeping the battery up will depend on what size wire was used for the 12v supply back to the 7 pin.

That is a very interesting "if" there Grumpy. I know my 1990 GMC Suburban was a 10 gauge wire for the "charge line." The 2014 Ram we have now needs to be looked at. Thank you for bringing the wire size up. I will have to look.

[oh355mbqs]

I have an Eagle fifth wheel with the residential refrigerator. Camper came with a 1000 watt inverter from the factory. I have had very good luck with this setup. I have driven 8-10 hours and the batteries were still perfectly charged, showed over 14 volts. I do have 2 deep cycle batteries, my truck was wired from the factory for charging, I have no idea what size the wire is. I also tested the system not hooked to my truck, went 6 hours and never lowered the voltage on the batteries either.

[nighthawk87]

Originally Posted by jamaddox

Just kinda nervous still on running with propane. Makes me think of running with scissors

What are you worried about happening?

[jfg]

Originally Posted by nighthawk87

I run with the propane on all the time. Seems to ruin the point of having a fridge if I can’t use it when traveling

This is what we do as well. Just make sure to turn off the propane before driving into the gas station or in a tunnel.

[klassic]

Originally Posted by oh355mbqs

I have an Eagle fifth wheel with the residential refrigerator. Camper came with a 1000 watt inverter from the factory. I have had very good luck with this setup. I have driven 8-10 hours and the batteries were still perfectly charged, showed over 14 volts. I do have 2 deep cycle batteries, my truck was wired from the factory for charging, I have no idea what size the wire is. I also tested the system not hooked to my truck, went 6 hours and never lowered the voltage on the batteries either.

I don’t know how you managed that.
No way can I do that with my residential fridge.

[Cannon]

Longest I've towed with my residential fridge is 7hrs. When I left home it was -6 and 34. When I arrived at campground it was still -6 and 34

[jamaddox]

Originally Posted by Cannon

Longest I've towed with my residential fridge is 7hrs. When I left home it was -6 and 34. When I arrived at campground it was still -6 and 34

Was it running? Do you know what the ambient air temp was? Did you put in any ice to help it? Right now we are not using our camper to go on long trips during the summer but we may soon

[bigironcoder]

Something else to keep in mind - in every RV I've had the frig held its temperature much better on propane. In fact, I've had to switch a frig to propane when it was really hot outside, even when I was plugged into electrical power.

Even though people do it all the time, I agree it's not wise to leave the propane on in a gas station or tunnel.

[SkyBound]

These gas absorption fridges run very efficiently on propane. I find mine cools much better on gas than AC power anyway. I have always had the propane burning while driving and never had a problem. I will, however, shut the propane off when refueling or if we stop and park and the trailer is not reasonably level.

[Cannon]

Originally Posted by jamaddox

Was it running? Do you know what the ambient air temp was? Did you put in any ice to help it? Right now we are not using our camper to go on long trips during the summer but we may soon

Ambient temp was in the 60's. No ice and very little food in fridge or freezer.

[Subaru297]

Keep in mind the duty cycle of a refrigerator is not 100% when doing calculations. Sure it can draw 30amps from the batteries but for how long?
If it is on only 15% of the time that is only 4.5 amp hours per hour. Easy for a trucks charging system to make that up while towing.

Here is a link that shows 11 amp hours (per hour) usage while running. Even that should be fine to maintain while towing.
https://www.gonewiththewynns.com/rv-...igerator-power

[SloPoke]

Originally Posted by Subaru297

Keep in mind the duty cycle of a refrigerator is not 100% when doing calculations. Sure it can draw 30amps from the batteries but for how long?
If it is on only 15% of the time that is only 4.5 amp hours per hour. Easy for a trucks charging system to make that up while towing.

Here is a link that shows 11 amp hours (per hour) usage while running. Even that should be fine to maintain while towing.
https://www.gonewiththewynns.com/rv-...igerator-power

Think about how the rated consumption of a residential fridge is calculated where the fridge is in a controlled environment at a constant 68-degrees. the unit only runs when the interior thermostat calls for cooling when the temperature rises above the set-point. Now where the typical RV Fridge is installed right against an outside wall with limited insulation, in a hot environment inside a closed up trailer w/o any AC running. Will the duty cycle be the same under these different conditions? Not with the heat-load being much higher in a RV.

Also note that the 4.5AH rating is at 120vAC - that equals 540W. An inverter will draw more than 45A from the batteries at 12vDC to power that same load. I have never seen a TT or 5er that has a charging cable big enough to handle that load from the tow vehicle. Also consider that we have not even factored in a defrost cycle or cabinet heaters into the equation.

[jamaddox]

Okay so with all of the above info then how do motor homes do this. Do they have bigger batteries or is the assumption that people will run the generator while driving? Or do they run with propane with the potential accident dangers