Electrical Help Needed: Running a large dorm fridge off of a 500w inverter.

[007matman]

My camper has one of those larger dorm-style fridges in place of an outside kitchen fridge. I would like to be able to run the fridge off of the trailer batteries when traveling.

I ran 12GA wire from the fuse panel to the rear of the camper (about 20 feet) and then connected the inverter directly to that. I have a steady 12.7v at the inverter. However, as soon as I turn on the fridge, the voltage drops to 9.6. the fridge attempts to run but alas, the inverter kicks it off. I have not popped any fuses.

I tried connecting the inverter directly to the camper batteries and then running a 120v (50') extension cord to the fridge and that worked.

According to the labels, the fridge only pulls 110w and 1.3A.

My inverter is a 500W pure sine inverter.

Any thoughts/expertise here? I'm stumped. Is this a classic case of voltage drop? Any way to compensate for this?

Thank you in advance.

[dagst1]

I would mount the inverter as close as possible to the battery / batteries and run at least 8 gauge wire if under 10 feet or 6 gauge if over 10 feet. Then run the shortest extension cord or hard wire a plug for the refrigerator. Use a breaker between the inverter and the battery. Also check if your inverter has a breaker on the output/120 volt side.

[DannyZeee]

Originally Posted by 007matman

My camper has one of those larger dorm-style fridges in place of an outside kitchen fridge. I would like to be able to run the fridge off of the trailer batteries when traveling.

I ran 12GA wire from the fuse panel to the rear of the camper (about 20 feet) and then connected the inverter directly to that. I have a steady 12.7v at the inverter. However, as soon as I turn on the fridge, the voltage drops to 9.6. the fridge attempts to run but alas, the inverter kicks it off. I have not popped any fuses.

I tried connecting the inverter directly to the camper batteries and then running a 120v (50') extension cord to the fridge and that worked.

According to the labels, the fridge only pulls 110w and 1.3A.

My inverter is a 500W pure sine inverter.

Any thoughts/expertise here? I'm stumped. Is this a classic case of voltage drop? Any way to compensate for this?

Thank you in advance.

Voltage drop is your problem, there are a couple of ways to overcome this. Your 12 gauge wire is too small. You could try a larger wire to the inverter(at least an 8 or a 6), you could install a large, low ESR capacitor, very close to the inverter(expensive, if you don't have one lying around), or, another battery close to the inverter(a smallish LiFePO4 would shine here), or, move the inverter close to the battery, and wire a 120V line to the fridge. You could also install a softstart on the fridge, but, that is major overkill for such a small load.

Just thought of an easy way, your battery is likely connected to your DC load center by at least a number 6 cable, just run a 6 cable from your load center to the inverter(or, multiple runs of number 12, if that is all you have, just try to keep the lengths of 12 all the same length). Depending where your load center is, it may be very close to the fridge anyway. (mine is <3' from the fridge.)

[Lloyd]

I agree, you don't have heavy enough wire for the length of run.
Both of the previous posts gave you some good ideas to try.

[007matman]

Thank you all for your responses.

I just ordered 10' of 8ga wire. The first plan is to see if I can get it from the batteries into the front storage compartment. I don't think it's going to be an easy task based on previous experience. This camper is sealed up really well and it doesn't seem to have any removable panels to gain access.

The other option might be to just try running that into the fuse panel (with a much shorter length) and then running a short extension cord to the fridge. My camper has a rear bunkhouse/living room.

I would probably hook it up temporary to see if it works with those lengths before I went to all the work of routing that wire.

Trying to leave for vacation on Friday for two weeks. Hoping I can make this work.

Thank you all again for your responses. I really appreciate it.

[007matman]

Anyone have an idea how our campers are constructed in the front under the cap?

Any way to get a wire from the batteries through to the storage bay?

I'm stumped.

I would straight up drill a hole from the storage bay to the underbelly, but in order to do that I'd need to be about 6" away from the interior wall ( inside the cubby). That would be an issue I would think with things getting snagged and the wires getting moved.

Open to any suggestions..


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[dagst1]

The existing battery cables can you follow them to where they enter? If the inverter is mounted on the front wall of the storage can you go straight down thru the floor and then out to the battery? Just a few ideas.

[007matman]

Originally Posted by dagst1

The existing battery cables can you follow them to where they enter? If the inverter is mounted on the front wall of the storage can you go straight down thru the floor and then out to the battery? Just a few ideas.

The problem is that the storage compartment inside actually is in the fiberglass cap. In order to get the wiring into the enclosed area (underbelly) the wires would need to be drilled through the floor about 9" from the inside wall of the storage compartment. This would get it inside the frame rails.

After this was done, I'd end up with wires coming up out of the floor 9" away from the wall. I'm worried they'd get damaged. I thought about building a small "chase" on the floor to get the wire to the wall but I don't like the fact that it would ruin my flat floor.

I really wish there was a way to get it through the wall inside and then through the cap, but as you can see from the photos, the cap extends under the camper.

I'm the end, the chase may be a way to do it. I was hoping someone else may have done this and had some ninja method of routing wires through the cap.

[Yakherder]

I am not positive on where the wire is to run once inside the trailer but I see from the pictures there are two knock-outs in the frame just behind the battery box. You could run the wire from the battery through one of these and fish it through the underbelly and bring it up where ever it is needed. I believe there are grommets you can use to plug the hole to make it water tight with the wire in the middle of it.

[007matman]

An update..

We're on vacation now and I was able to finish the morning we left.

I did run it through the frame (actually using the same hole the other trailer wiring runs through to the tongue).

I did drill a couple of holes in the floor through to the underbelly and then ran the wiring up. I made a "wire chase" on the floor to cover the wires and route them to the wall where I mounted the Inverter.

I have about 4' of both black and red 8ga wire that I ran. Then I have a heavy 50' extension cord ran to the back of the trailer. I'm contemplating cutting some off so it's as short as possible..

It's not perfect, but it works..

I'll post a pic later.

[dagst1]

Thanks for posting your solution.

This way your trip is not interrupted and later if you find a different solution you can always make the changes.

Enjoy your trip and safe travels.

[Yakherder]

Good to here you got it done and it works. Those are the magic words to any job.