New Boat/Travel Refrigerator Suggestions for 2026

[OverEasy]

Hi Be Free!

Great write up!
Nicely done!

Most of the stuff I’ve had the opportunity to deal with in regard to commercial recreational consumer products are ‘native’ 12 VDC as it’s the most common source of power and suitable for most of the sourced sub components readily available. Even with the widespread availability of DC-to-DC converters many (budget) manufacturers still use a dropping resistor to lower voltage from 24 VDC to 12 VDC as its reliable and cheaper.

I have noticed that many of the manufacturers, when they offer a 12 or 24 VDC option on the same unit, will have the AC transformer adapter output set to the ‘native’ voltage. So that could be a clue if someone was interested in finding out what they might be dealing with. Not a guarantee, just and indicator.

Glad Russ mentioned the effect of wire gauge and length of wire run, both to and from the battery to the device. Some DC wiring systems have negative side return runs different than the positive side supply runs. The total length of the complete wire run from the battery and back will determine the effect on line power losses. The larger the wire diameter the lower the incurred losses. (Hint for those wondering: Wire gauge size is sort of counter intuitive for most folks… The lower the gauge number the larger the cross section of the actual conductor wire…. Hence as wire cross section increases the less resistance to current flow)

In our situation in Over Easy we previously mostly ran our old Thermonic fridge on shore power as the unit had pretty good insulation. When using it on road trips I found that the unit drew enough current to occasionally pop the fuse for the rearmost DC outlet while if we used the DC outlet up front this wasn’t an issue.

I’m very much considering adding dedicated heavier wires for both the vans and the boat with a dedicated circuit breaker outside the existing wiring bundles. That way I can route all the wiring more directly for shorter lengths and pre-emptively avoid any wire heating issues. My only concern is in where to mount the switch/circuit breakers where they are closest to the battery but still readily accessible.

I really am appreciative of all the suggestions and help recieved on this topic so far.
Thank you!

Best Regards,
Over Easy

[Be Free]

The main advantage to using 24V is that the wiring can be (approximately) half the size required by 12V for the same load. Smaller wire is less expensive and easier to run. It's not likely to keep you away from the low voltage problem though. The unit will still struggle to start around 23V and will probably shut down around 21V. This is to keep internal components from overheating and to protect your battery from being overly discharged.

In a DC circuit Watts = Volts x Amperes. The power required to run the refrigerator (Watts) does not change but as the Voltage drops the Amperes have to increase. As the Amperes (current) increase more heat is generated in the circuit. Eventually, something in the refrigerator or a fuse on your panel is going to trip and shut things down. The normal progression is struggle-to-start followed by low voltage shut down regardless of the initial voltage. The only difference is the set point for the low voltage alarm.

Interesting points. The "heat" from the wiring is interesting. My 12v fridge was struggling until I upped the gauge of the wires and moved it closer to the battery. I suspect voltage drops caused big problems. No doubt there was some energy loss in the wiring as heat.

It would be interesting to learn the native voltage of the compressor. If it is stepping down to 12 from 24v, that would make no sense to supply it with 24v for reasons you mentioned.

Most electronics seem to offer 12-24v range of DC supply. Virtually all AC electronics will run on 110 or 220v. They step it all down to some form of DC, usually in the USB voltage ranges.

All of the power (Volts x Amps) will either be used for something productive (running your compressor) or it will be used to make heat in the wires and other components, maybe some sound or light (but mostly heat). The only thing you have control over is the resistance in your wires which is directly proportional to the length and inversely proportional to the thickness (cross section).

When you upped the gauge of the wire you decreased the resistance which decreased the voltage drop. For instance, going from a 12AWG to an 8AWG would drop the resistance in the circuit by about 1 Ohm per thousand feet of wire. That doesn't sound like much but it is a little over 60% reduction in resistance which will result in a little over 60% reduction in voltage drop. Keeping in mind that the difference in voltage for a lead acid battery going from 100% to 50% charge (effectively dead) is about 4.5%, a 60% decrease in resistance is significant.

Shortening the run was a good idea and it did help but to get the same 1 Ohm drop in resistance in a 12 AWG wire you would have had to shorten it by over 600 feet. Making it fatter got you the most bang for the buck.

(FYI: I wrote this at breakfast this morning and forgot to hit submit )