Running a Trailer Refrigerator from an Inverter While Towing

[Ex-Calif]

I am outfitting my trailer and installing a 400w inverter to run tv and google tv when generator is not allowed.

Would it be crazy to plug reefer into the inverter while underway? The truck will be providing 14v to the trailer for charging any way...

We will be boondocking fir 6 days. While stopped we can run the genny except overnight - restricted from 11pm to 7 am. I am planning to run genny off and on to keep fridge cold "enough"

 

[DonTom]

I am outfitting my trailer and installing a 400w inverter to run tv and google tv when generator is not allowed.

Would it be crazy to plug reefer into the inverter while underway? The truck will be providing 14v to the trailer for charging any way...

We will be boondocking fir 6 days. While stopped we can run the genny except overnight - restricted from 11pm to 7 am. I am planning to run genny off and on to keep fridge cold "enough"

Do you mean only 400 watts or did you mean 4KW?

What type of refrigerator? That is the main thing.

In an absorption type refrigerator on 120 VAC, the heating element alone draws around 330 watts. A small compressor refrigerator can probably do better with less watts on 120 VAC, but look at the rating labels--a good place to start.

I need a few more details. But if you know the AH or WH capacity of the battery, the efficiently of the inverter, the total current draw of the refrigerator, etc, you should then be able to figure out how long you can operate the refrigerator from a fully charged battery while it is NOT being charged.


-Don- Baker, NV

 

[Ex-Calif]

I'll double check the draw tomorrow. The internet says a fridgidaire compact draws up to 3 amp continuous.

Also the idea is not to run off battery. Only while underway with truck supplying the juice.

I think the alternator on my truck is 180 amps. 220 is an option.

400w inverter /12v = 33 amps.

This inverter will be at max capacity. There is a 600w or 800w unit I can exchange for as well.

My question is driving 40 amps thriugh the trailer plug wiring...

 

[DonTom]

I'll double check the draw tomorrow. The internet says a fridgidaire compact draws up to 3 amp continuous.

At 120 VAC, that is 360 watts. Your inverter could be flakey when that close to its max rating. I find a lot of inverters will not do their full "continuous" ratings for more than a few seconds.

-Don- Baker, NV

 

[bigbAZ]

I'll double check the draw tomorrow. The internet says a fridgidaire compact draws up to 3 amp continuous.

Also the idea is not to run off battery. Only while underway with truck supplying the juice.

I think the alternator on my truck is 180 amps. 220 is an option.

400w inverter /12v = 33 amps.

This inverter will be at max capacity. There is a 600w or 800w unit I can exchange for as well.

My question is driving 40 amps thriugh the trailer plug wiring...

The charge wire to the trailer would have to be pretty big to get that much current that distance. How far is it from the truck battery to the trailer battery box, and what chemistry is the trailer battery bank and what is the amp hours? What size is the charge wire in your 7 way and what is it fused at? All those things need to be known in order to answer your question accurately without guessing.

 

[DonTom]

My question is driving 40 amps thriugh the trailer plug wiring...

If copper 8AWG will do. If anything else, you want 6 AWG. You probably have 14 AWG for the trailer wiring, so it is not going to be thick enough.

-Don- Baker, NV

 

[RayIN]

If copper 8AWG will do. If anything else, you want 6 AWG. You probably have 14 AWG for the trailer wiring, so it is not going to be thick enough.

-Don- Baker, NV

I agree, amperage is more important than voltage, but they are inseparable.

 

[DonTom]

I agree, amperage is more important than voltage, but they are inseparable.

That was a cute cartoon that I have never seen before.

When it comes to fuses and wire sizes, it is mainly the amperage that counts. Fuses only have a voltage rating for safety for when they blow so they will not arc over.

I think that is the only reason why the supply power side is often rated in amps, but the load end is usually rated in watts.

But you can have voltage with zero amps, but you cannot have amps or watts with zero voltage. So which is really the most important? Without voltage we have nothing possible in electronics or electricity.


-Don- Baker, NV

 

[RayIN]

That was a cute cartoon that I have never seen before.

When it comes to fuses and wire sizes, it is mainly the amperage that counts. Fuses only have a voltage rating for safety for when they blow so they will not arc over.

I think that is the only reason why the supply power side is often rated in amps, but the load end is usually rated in watts.

But you can have voltage with zero amps, but you cannot have amps or watts with zero voltage. So which is really the most important? Without voltage we have nothing possible in electronics or electricity.


-Don- Baker, NV

I agree. I was thinking of the end of the battery charging circuit. The voltage is there but amperes are restricted.
That picture is not mine. It's from an old WWII Navy electronics training manual; originally posted 25 yrs ago on irv2.com by a member.

 

[Ex-Calif]

Yeah. I have a wiring vs load chart some where but was lazy to find it.

I reckon 30 amps at 12 volts is not gonna work out through the trailer lights plug.

Now I am curious about the whole house battery charging system. I know there is a Xantrax converter that charges the battery on shore power but not sure how house is wired in to truck supply.

On my 2 day to departure checklist is to d/l all the component manuals and print the key ones out. My printer ran out of ink printing the owners manual.

I stupidly and accidentally bought reman ink that was dry out of the box. I got new oem ink but its buried in my pikes of provisioning in the truck.

Option 2 - I might run the genny in the truck bed under way.

The 30 amp cord reaches right up to the ball. I can run the second cord from the genny to the ball and pkug in.

Is that a stupid idea?
.
I'd also like to get a feel for the genny fuel burn until empty...

 

[Lou Schneider]

The problem is voltage drop along the charging wire. Even if it's rated for 30 amps (10 gauge) you'll lose anywhere from 0.5 to 1 volt by the time it reaches the trailer battery.

If the wire can handle the current, you can correct this by adding a DC-DC converter at the trailer battery. Typically they will produce a constant 13.5 volts out with anywhere from 9-16 volts at it's input.

 

[Mark_K5LXP]

I've run my 300W evaporative fridge while underway from a 12V inverter for years now. Trailer wiring adds a complication. The practical answer is to put the inverter as close to the source as you can and run 120V to the trailer, either the shore input or dedicated fridge line. Maybe just a basic 15A plug/inline socket at the trailer connection point. Connect or not connect as needed. Genset in the bed can work fine too if you don't mind it hammering away back there. No different than running my generator for A/C underway. Being a compressor fridge you might experinment with how much it runs to maintain temperature. You could discover there is some amount of time you can let it slide and maybe run the genset when stopped on a break or whatever. Thermal mass helps carry you too, loading up with ice in the freezer and some in the fridge can slow the warm up time. A basic remote thermometer can tell you a lot and aren't expensive.

Mark B.
Albuquerque, NM