Inverter to run outside fridge

[mhsmith]

I want to keep my outside kitchen fridge cold for longer distance travel. I am curious if anyone has done this or can it be done? Would be a short run on the 12 volt wires to my convertor. Reason I am considering this is so while travelling we can put some drinks and food in it so I don't have to open the slide when stopping for lunch or a snack as the fridge is in the back and blocked by it.

[mhsmith]

Appreciate all the info. Did some more digging and found more info on fridge and it could require up to 575watts startup. With battery in the front and fridge on the rear its just not worth it for one trip from Ohio to Texas. Was talking to guy I work with and he offered a powered cooler for me to borrow so that will be the ticket for this trip. Thanks again.

[Gdetrailer]

mhsmith wrote:

time2roll wrote:
Cooler could also be a set of ice packs in the outdoor fridge and let it be without power.
Put the icepacks in the freezer inside overnight to be ready the next day.

Have done this on shorter trips(2-2/12hrs)

Supersize the "ice packs".

Larger mass of ice takes much longer to melt, the larger the cubes the longer it takes to melt them..

Instead of the small reusable ice packs, freeze a few water bottles. I have in the past made 1 quart "ice cubes" using simple 1 quart "freezer" containers. In a ice chest those oversized cubes would last several days easily in 95F+ temps..

Good chance you will want some water so when melted, the water bottles can due double duty as drinking water supply.. Nothing goes to waste and your refreshments stay cool..

[mhsmith]

BFL13 wrote:
You have a truck towing a trailer. It is just to keep the drinks and some food cold while driving till you can get 120v for the fridge.

You can try the inverter route with some difficulty as others have posted.

Another way is just have a "cooler" that could hold about as much as the outside fridge in the trailer does. Cooler powered from the truck's 12v system. A DC-DC converter might be useful in that role, but maybe not necessary. Cooler could be inside the cab or in the box.

"Cooler" could even be another small 120v fridge in the back of the truck box with inverter, where the inverter is powered by the trailer batts on the tongue via fat- wire jumper cables.

Might even be able to use the same fridge by just carrying it back and forth between the truck and the trailer if it is not installed in the trailer in an awkward way.

This may end up bein they to go. Just didn't want to add more weight than necessary but it is the simplest way to do it.

[mhsmith]

time2roll wrote:
Cooler could also be a set of ice packs in the outdoor fridge and let it be without power.
Put the icepacks in the freezer inside overnight to be ready the next day.

Have done this on shorter trips(2-2/12hrs)

[time2roll]

Cooler could also be a set of ice packs in the outdoor fridge and let it be without power.
Put the icepacks in the freezer inside overnight to be ready the next day.

[BFL13]

You have a truck towing a trailer. It is just to keep the drinks and some food cold while driving till you can get 120v for the fridge.

You can try the inverter route with some difficulty as others have posted.

Another way is just have a "cooler" that could hold about as much as the outside fridge in the trailer does. Cooler powered from the truck's 12v system. A DC-DC converter might be useful in that role, but maybe not necessary. Cooler could be inside the cab or in the box.

"Cooler" could even be another small 120v fridge in the back of the truck box with inverter, where the inverter is powered by the trailer batts on the tongue via fat- wire jumper cables.

Might even be able to use the same fridge by just carrying it back and forth between the truck and the trailer if it is not installed in the trailer in an awkward way.

[2oldman]

Another possibility to handle the surge with smaller wire is to up your inverter input voltage to 24 or more, but, that's not something most people even consider.

[mhsmith]

I thank everyone as this is the kind of info I need to determine if I can do it or suck it up and leave it. Gonna need to do some testing at this point and once again...thanks.

[MEXICOWANDERER]

Split phase motors frequently demand 500% of run current to start. If you design your inverter circuit for 500 watts you will lessen the certainty of failure.

[Gdetrailer]

wanderingaimlessly wrote:
The fridge wont be running all the time, so yes it's doable. But your power number seems low.
Get one of these Kill a watt or something similar and actually measure what the amps/watts are on start up so you don't buy too small an inverter.

To be clear, OP was wanting to use existing wiring to the fuse panel and or 10 ga wire.

None of that wiring will be able to support the startup surge of a highly inductive load from the fridge compressor.

As long as the OP uses a heavier wire and not the existing wire and they mount the inverter as close as possible to the batteries of course "it can work".

I am speaking from experience as I studied and worked through this problem for quite some time before I committed money to parts.

I HAVE measured my fridge running current AND the startup surges, while a small inverter on paper would look like it "should" work, it will not because of the surge current.

Others on this forum who faced this issue had also tried many small inverters from 300W to 500W.. Those small inverters all had issues with startup surge, general consensus has been around 700W inverters tend to have better results.. and the larger the inverter above 700W the better results you will get. That is why I recommend 1000W inverters for this job even though most of the time the fridge will be using less than 1/10th of the capacity of the inverter.

The difference in cost between a 500W inverter and a 1000W inverter are not all that great. Your talking often only about $60-$100 more for a 1000W inverter over a 500W inverter.

Fridge compressors are a very complex current device unlike say an incandescent light bulb. Incadescent lights pose nearly no surge current so you can run an inverter right near the max rating, fridge compressors however, not so much.

[time2roll]

mhsmith wrote:
120 volt fridge. Rated at 1.1 amps which gives me 132 watts. I am looking at possibly a 180w to 200w inverter.

I think you will be disappointed. I would guess 600 minimum and #6 wire.
Hard to know surge requirements with motors. These small fridges are notorious for large start requirements. The full length of wire to the battery will work against you to provide the required volts and amps the inverter needs.

That kill-a-watt will not measure surge current.

[wanderingaimles]

The fridge wont be running all the time, so yes it's doable. But your power number seems low.
Get one of these Kill a watt or something similar and actually measure what the amps/watts are on start up so you don't buy too small an inverter, or use too light of wire.

[Gdetrailer]

mhsmith wrote:
I was looking at 10g wire minimum to to inverter. Thanks

Nothing like planning for failure..

10 ga isn't going to cut it even if it was 2 ft in length, will drop way to much voltage under the startup surge.

A 1.1A at 120V rated fridge compressor can have as much as 10A at 120V start up surge. That is roughly a 100A at 12V surge and not only does your inverter need to be able to handle it, the wiring and battery must be able to support that surge.

You WILL need an inverter rated at a min 800W CONTINUOUS but I would recommend a 1000W continuous rating. This gets you past the elcheapo inverters which have false surge ratings to make them sound better.

For the wiring, you NEED to mount the inverter as close to the batteries as possible to keep the 12V wiring as short as possible. The longer the 12V wiring, the heavier ga of wire you will need and at todays wire prices short as possible is your wallets best friend.

With a potential of a 100A at 12V surge your looking at 2 ga at a min for not much more than 10ft total (5ft for negative and 5 ft for positive). I personally used 1/0 and it is just under 8ft total for my home fridge conversion.

There is no shortcuts to this otherwise you will end up with lots of frustration when the inverter shuts down from low voltage.

Cheapo inverters are also a "hit or miss" thing, many of those low priced imports are way overstated on their ratings, choose cheap and you get cheap and less than reliable results.

If you are using a single group24/27 RV/marine battery you will need to consider MUCH MORE capacity since the tow vehicle charge line will not be able to support and keep up with the discharge rate..

I am using a pair of 6V GC2 batteries on my setup, works like a charm and is dependable.

[DrewE]

mhsmith wrote:
120 volt fridge. Rated at 1.1 amps which gives me 132 watts. I am looking at possibly a 180w to 200w inverter.

Required starting power for the fridge compressor is probably a lot higher than that; a 600W to 1000W inverter is often the minimum size that will work reliably for a fridge, even a small fridge. The running power is much less than the starting power.