Fridge options 12v vs 110v

[brianjonesphoto]

Talk to me about refrigerators. Trying to decided between a pure sine wave inverter running a 2ish cu ft mini fridge vs a 12v fridge. Is there enough efficiency difference to jstify the extra cost of the 12v?

How many amp hours a day does your fridge set up consume?

I likely have a 100ah lithium battery bank no solar planned for now. I doubt we will ever have hookups. I can foresee running a generator for about 3 hours a day while charging electric motorcycle batteries.

Thanks.




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[John61CT]

Do you mean the motorcycle(s) are battery powered, or do they have ICEs?

You will need maybe 200Ah of LFP storage for an inefficient AC fridge.

A proper 12V compressor fridge really is required once you want a sensible mostly-solar setup.

Not expensive, compared to running genset a lot, and the quiet is nice.

[flboy]

12vdc Fridges are nice and the best choice if the overall power efficiency is all you are concerned with. If you already need an inverter for other things and plan on having a solar array, I'd go for a good dorm fridge and throw on one more solar panel to cover any inverter efficiencies ( if it even matters) and call it a day. You could get a 4.3 cu ft. Fridge and a 100w solar panel for less than half the cost of a similar sized DC fridge.

If you need the inverter just for the fridge... I'd consider the DC fridge as you have less to possibly go wrong from an electrical perspective and do not have the standby current of the inverter or the conversion loss (minimal.. but real) just for the fridge.


It all depends what your needs are and what your budget can take.

I knew I was going to have a decent sized inverter and a good solar setup from the start, so for me , it made no sense to pay a premium for the DC fridge when the solar power is free once you have the equipment. The inefficiency doesn't hurt you in this case. I picked up a 4.3 Cu ft. Magic Chef on sale at Home Depot for $129.00 and it has served me well. Uses 45 watts when running so it is very efficient, but that does not count the inverter hit.. It has a good freezer compartment that will freeze meat and keep ice cream hard. Very happy with it.


BtW, just reread your post and you sound like the DC fridge would be better for your plans, but the above is how I'd arrive at the decision.



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[brianjonesphoto]

Do you mean the motorcycle(s) are battery powered, or do they have ICEs?

Correct fully electric. Both my kids ride Oset bikes. A 16” and a 20”. Both lithium powered. No practical way to charge them besides 110v.


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[John61CT]

Silly thing to say, but OT here anyway. Practicality is in the eye of the beholder, so nevermind.

Completely agree though since you need kW charging for that use case, a couple hundred Ah extra stored to enable using an inefficient AC fridge is NBD.

Personally I'd want to standardize the LI packs so they can be used for both purposes, DC buck converters can be very cheap.

Hobby chargers like FMA Cellpro PL8v2 or iCharger 4010-Duo are excellent for general testing / balancing / maintenance of pretty much whatever chemistries you use.

[Pinstriper]

Just to drift a bit, is there a good reason propane fridge is not in the consideration ?

It does sound to me, however, like a 110v that switches over the 12v once cold and while the generator is off would be your path, since you are going to be in the generator business already.


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[John61CT]

It does sound to me, however, like a 110v that switches over the 12v once cold and while the generator is off would be your path

Doesn't work that way. Internally everything works the same internally on DC, the unit just includes circuitry that rectifies the AC input, like a converter / charger.

That imposes an efficiency hit.

Which is not relevant with big gensets running daily anyway.

> Just to drift a bit, is there a good reason propane fridge is not in the consideration ?

They use thermal absorption, not a compressor, totally different technology.. Switching over to any electricity to produce the heat is hugely inefficient.

[McDave]

You are getting some good advice and info here. Just to clarify 12vdc/120vac units are really just 120vac units with a built-in inverter. LP/12v units are absorption reefers that either use 12vdc to operate controls only, or some can use 12vdc to heat the ammonia also but are very inefficient in 12vdc mode. 12vdc/120vac/LP reefers are absorption reefers that use LP or 120vac to heat the ammonia, and 12vdc to operate controls. There are thermoelectric coolers, but they are not refrigerators. More like an ice chest without Ice. No freezing and limited cooling. In general, chest type are more efficient than door type because the cold air wont fall out when opened.

McDave

[RJ Howell]

I have a 3.7 cubic foot 3 way frig and on batteries it uses 10.7amps an hour or 256amps in a 24hr period. I use it in propane mode and use .12 (120ma) or 2.88 amps in a 24hr period. I like propane...

[onehoser]

I have a 3.7 cubic foot 3 way frig and on batteries it uses 10.7amps an hour or 256amps in a 24hr period. I use it in propane mode and use .12 (120ma) or 2.88 amps in a 24hr period. I like propane...

i'm liking the sound of propane too but it's going to have to be later in my build so that i locate it in the right spot the first time lol! can't be cutting holes all over the place. can you run it on propane while towing? or will it blow the flame out?


tony

[troubleScottie]

no having one, I doubt it would be recommended to run on propane while driving. Open flame, tip over, extinguishing the flame, propane into cabin to name a few of the problems. Hence the electrical power access.

To that end, you could power the frig/charge your TD battery(s) while driving. Thus counteracting the expenditure. Lots of ideas on how to make this happen.

[RJ Howell]

I have a 3.7 cubic foot 3 way frig and on batteries it uses 10.7amps an hour or 256amps in a 24hr period. I use it in propane mode and use .12 (120ma) or 2.88 amps in a 24hr period. I like propane...

i'm liking the sound of propane too but it's going to have to be later in my build so that i locate it in the right spot the first time lol! can't be cutting holes all over the place. can you run it on propane while towing? or will it blow the flame out?


tony

I do now all the time. It's just that efficient on propane. Maybe the older styles had issues you mention.

[RJ Howell]

no having one, I doubt it would be recommended to run on propane while driving. Open flame, tip over, extinguishing the flame, propane into cabin to name a few of the problems. Hence the electrical power access.

To that end, you could power the frig/charge your TD battery(s) while driving. Thus counteracting the expenditure. Lots of ideas on how to make this happen.

You'll fine it's a split on who does and does not. I do. In my other three traveling forums it's 50/50 yet no one has had the issues you mention. I do believe those are of days past.. As for charging the refrigerator while driving, well all good if you travel each day.

The size battery bank (excluding lithium) required is heavier than the propane, does run as efficiently and propane opens up to even more uses. The only time I come off propane is that rare occasion I get a site that has shore power.

Just my opinion from my use of both, propane & battery.

[John61CT]

It is illegal to be running on propane while driving in most jurisdiction, for obvious reasons. Pilot lights blow out, lines leak. . .

Pulling into a FF station with a flame active, you'd have to have some sort of death wish.

Really IMO the days of propane fridges in a mobile context should be behind us now full stop.

But with all the power an alternator is putting out I can't see why you would not run off that while traveling?

[onehoser]

great info! will definitely help me decide which direction i will go in...