24 or 12v for fridge running on inverter...

Hi Guys,

So I want to run a domestic fridge in my van through a 1200w pure sign inverter.

I plan to have 2 x 100 amp hour lithium batteries wired at 24v to power the fridge and a separate 1 x100 amp hour battery at 12v to power smaller items.

2 x 200w panels will charge the 200ah bank

1 x 200w panel will charge the 100ah bank

Alternator charging will also charge the 200ah bank.

Is this a good idea or am I over complicating things?

Would there be less losses running the fridge at 24v?

I know the obvious answer is a 12v fridge but at my required size, they're just way to expensive...

Cheers guys!



Is this a good idea

24v Great Idea. Higher voltage inverters tend to be more efficient and produce less heat.

I think it would be cheaper and more efficient to have 1 300Ah bank if your batteries could be configured that way.

This way you have one SCC and 1 battery you can still run all 300 watts of panels to the SCC and one battery. for the 12 v loads just get a 24v to 12v DC converter they are cheap on amazon or ebay.

I just think that 1 system will be easier to manage than 2 systems as you propose. But your proposal will definitely work.

Can you detail which exact Dometic Fridge you are planning. Yes, upfront costs can be higher for compressor type fridge, but long term the reduction in power needed can minimize the need for panels and related equipment, including battery capacity. Need to do some cost/benefit analysis to look at alternatives.

What I am reading doesn't really support the need for two battery systems at differing voltage domains.

The Waeco Dometic fridge is the 12v compressor:
£860 (about 1000 bucks)


The domestic/pantry fridge is 240v:
I think its rated at 169kwhpa
£149 (around 195 dollars)


I think a single 300ah bank is best with a step down to dc12v as Craig suggested?

I would have to ignore the alternator charging due to vehicle battery at 12v and leisure at 24v otherwise the alternator would be confused? Don't want to get into changing the alternator...

Did I mention it's in a camper van?

I'm full time in the van and we don't get as much sun over here in the uk. Effectively none for 6 months of the year.

I want a larger lithium bank as I'm away from shore power for charging for 4/5 days at a time and need more useable power.

Understand the upfront cost difference. But cost difference analysis needs to include related equipment costs to make a device choice function in use.
My point is analysis of system alternatives. The under counter fridge is AC device that will need an inverter to run off the DC batteries. Also, it is designed to have ventilation space on multiple sides. I could not find a installation specification sheet to determine the ventilation requirements.
This device will throw heat into the camper interior. Are your plans to be energy independent or shore power plug to shore power plug travel?

One point of analysis to consider is the actual energy use. More info is available on this site than I saw on Amazon.
https://www.thewrightbuy.co.uk/cook...-undercounter-2-door-fridge-freezer-in-silver

The amount of actual energy consumption needed at a baseline temp is critical to determine if system will truly support the device in your planned situation.

The fridge will have a separate insulated and ventilated 'room' at the rear of the camper with a couple of PC fans creating air flow, so it is not in the same space that the heater is servicing.

My understanding from wills videos is that 24v has less losses through the wiring and may (a little) offset some off the inverter loss?

JayGuevara said:

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My understanding from wills videos is that 24v has less losses through the wiring and may (a little) offset some off the inverter loss?

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The difference between 12v and 24v efficiency is very small. Additional technical research can help you understand the big picture here.

You have not identified any major dc electrical consumers that will take advantage of the 24v system. At these system size levels 24v just cost more to implement with little return other than a slightly smaller cabling and fusing requirement. If you were trying to run AC units or such the use of higher voltage would be beneficial.

One thing about Will's style - he throws out many facts but doesn't always link these facts directly to system implementation on a component by component level basis in an application. He always leaves implementation details to the individual.

All those details -fans and such are part of the upfront costs for the fridge device chosen. An argument can be made that some portion of the inverter and battery cost are part of the upfront cost of the AC fridge chosen, too.

I would simplify this way down ... just use a 12V battery system. No need for converters, multiple SCCs etc. Power the domestic fridge from the inverter - just make sure the inverter can handle the compressor surge (which a 1,200W inverter would most likely support).

If you do go with a 24V battery system you can charge from a 12V alternator using a DC-DC charger such as the Orion range from Victron (other manufacturers are available!).

The 12v system is probably simpler. But a 24V system has distinct advantages such as faster charging from shore power if possible. A 24v system could be charged twice as fast as a 12v system if you have access to shore power for only a short time. I honestly know nothing of the DC-DC chargers but I suspect here would be no advantage there of 24v over 12v. With solar you can get more watts through a smaller SCC if necessary and panels are available.

Craig said:

The 12v system is probably simpler. But a 24V system has distinct advantages such as faster charging from shore power if possible. A 24v system could be charged twice as fast as a 12v system if you have access to shore power for only a short time. I honestly know nothing of the DC-DC chargers but I suspect here would be no advantage there of 24v over 12v. With solar you can get more watts through a smaller SCC if necessary and panels are available.

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In this situation the install complexity ($$) shadow the benefits derived. Simple robust systems for mobile applications. I prefer to enjoy my travels -not babysit the RV systems.

These are not competing ideas - rarely is a solution black and white - but KISS is only a well known acronym because it works out more times than it doesn't ... just sayin'.

mapguy525 said:

In this situation the install complexity ($$) shadow the benefits derived. Simple robust systems for mobile applications. I prefer to enjoy my travels -not babysit the RV systems.

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I have no issues with a 12v system It will like we all say be easiest, However we also all know how things tend to grow after time so I also do not see a problem with a 24V system which would be easier to upgrade in the future if desired. I started with a 12v system and went to 24 now Im working on 48 but this is not a vehicular system either.
I am wondering about your comment about babysitting a 24v system vs a 12v system I cant see why one would be any more work than the other.

I am wondering about your comment about babysitting a 24v system vs a 12v system I cant see why one would be any more work than the other.

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Nothing to do with voltage domain choice. All about the complexity difference. Failure point number. Complex system more likely to need more human intervention -that could be out sightseeing at the needed time of human intervention.

I went up to 24v for my boat and run a domestic fridge (and freezer, both of which I got second hand) through an inverter, the whole set up minus the battery cost less than a 12v compressor fridge would have done.