Using an inverter to run a camping fridge

[roro36]

Take an average portable fridge that one would use for camping. It can run off 12Vdc/220Vac. Would it be wise to run an inverter off a battery and the fridge at 220vac off the car battery or would it be better to just run it straight off the 12V( Assuming all wiring, fuses and etc have been made to handle the current). Basically, fridge/freezers are double the price when it can run of either voltage, so I want to know if I can just buy the 220Vac one and then use an inverter while we only have the car to power it?

 

[Averagesupernova]

If the fridge is made to run off of 12 volts and that is all you have available then run it from that. Why would you convert to 120 VAC? All that will do is introduce extra loss in the system.

 

[roro36]

No, there are 2 types of fridges available. 1 - 12V or 220V supply, 2 - Only 220V supply. 1 costs twice as much as 2. If i purchase 12/220v then I can use 220V supply at campsites that have electricity, but in the middle of botswana there is often no electricity and we run the fridge off a deep cycle battery that charges while we drive. Now if I had to purchase the 220v only option, would it be fine to run the fridge off the battery using an inverter during the night and when ever the 220V is not available? I'm not worried about while we are driving becasue I assume that we can just use the inverter as the car is on, but at night to keep the fridge cold we use a deep cycle battery. This system works beautifully for a 12V/220V fridge but they are costly and I want to know if the power usage of an inverter would cause the battery to drain much quicker than using a fridge that can run straight from the 12V battery?

 

[amy8204]

it be better to just run it straight off the 12V,it is good to your firdge

 

[roro36]

Not sure you understand. What if the fridge doesn't have the 12V option. It only has the 220V. Now we usually use a fridge that has the 12V option and run it overnight off a spare battery while we are not driving. This works well. If we buy one with only the 220v option, will an iverter drain that same battery too fast or is this a viable way to do it?

 

[Wetmelon]

The 12V or 220VAC fridge probably has an inverter already in it, so it would be the same thing as running an inverter from the battery to the 220V only fridge.

Just make sure your battery can discharge fast enough and won't generate too much heat, and make sure the inverter can handle the power the fridge draws.

 

[theecoop]

i would say it depends on a couple of factors. what size battery bank(total batteries wired in series) what size inverter. most Rv type(camping refrig) are 2- way or 3 -way.
12v and 110 or 12v and 110 and lp gas. The refrig heating element(s) draw about 2.7 amps
usually the 12v portion is only used to help maintain the temp for a short period of time between being run on 120 v or lp.

 

[russ_watters]

It is likely that a 12VDC fridge would be more efficient than a 220VAC fridge running off an inverter.

 

[Ivan Seeking]

It is likely that a 12VDC fridge would be more efficient than a 220VAC fridge running off an inverter.

I wouldn't make that assumption. The losses go as I²R, so for the same power, we would expect ~20 times the losses due to heat, in a 12 volt system, as opposed to 220. Inverters are typically > 90% efficient, but low-volt motors tend to run lower than that.

 

[theecoop]

I wouldn't make that assumption. The losses go as I²R, so for the same power, we would expect ~20 times the losses due to heat, in a 12 volt system, as opposed to 220. Inverters are typically > 90% efficient, but low-volt motors tend to run lower than that.

Most camper type refrig cool with a heating element not a motor , for the 110 operation.

 

[sophiecentaur]

This presupposes that you can buy camping fridges which are designed to work basically on mains voltage. Isn't that a bit unlikely? CAmping very often involves being away from the mains.
I have recently been looking into small portable (compressor) fridges. Afaiaa all camping type fridges are basically 12V dc models and use an internal or external mains adapter.
btw, the 12V Peltier types are very heavy on current drain - although a small fraction of the cost of 'proper' ones.
Absorption type units (post#10) are still used in some applications (camper vans) because they use any heat source - either gas, mains or 12V electric elements. Not suitable at all for use in boats and also a heavy drain on a battery.

 

[theecoop]

I'm an RV Tech, have been dealing with refrigerators for camping for over 20 years.
12v is not a suitable source for cooling ( the 12v element) drains the battery to fast.
being that said, most of the time the 12v side is used when traveling a short period of time to help maintain the temperature inside the box. the battery is charged while driving from the alternator.
the 110 element is use when the unit is either plugged into a land source or using a generator. Very few manufactures used the inverter to power the refrig.

the 12v is also used to power the control board and the spark /gas valve operation.
most rv's have a 2 or 4 bank battery system (usually 2 6v batteries in series) then tied into the unit parallel . or the 4 bank system in series /parallel.
maybe this info will help you find your answer.
Im not an EE

 

[russ_watters]

I wouldn't make that assumption. The losses go as I²R, so for the same power, we would expect ~20 times the losses due to heat, in a 12 volt system, as opposed to 220.

If the wire sizes were the same, which they wouldn't be.

 

[sophiecentaur]

I'm an RV Tech, have been dealing with refrigerators for camping for over 20 years.
12v is not a suitable source for cooling ( the 12v element) drains the battery to fast.
being that said, most of the time the 12v side is used when traveling a short period of time to help maintain the temperature inside the box. the battery is charged while driving from the alternator.
the 110 element is use when the unit is either plugged into a land source or using a generator. Very few manufactures used the inverter to power the refrig.

the 12v is also used to power the control board and the spark /gas valve operation.
most rv's have a 2 or 4 bank battery system (usually 2 6v batteries in series) then tied into the unit parallel . or the 4 bank system in series /parallel.
maybe this info will help you find your answer.
Im not an EE

That's interesting. You're saying that RVs in the states don't use 12V compressor type fridges? They are so much more efficient and can even freeze stuff yet still take a modest current drain from batteries. On sailing cruisers, people just don't want to be running the engine all day and night just to keep the beer cold and the compressor type is much easier to support with a short daily charge, whilst motoring for a short while at the beginning and end of the day. Perhaps the RV market for 'real fridges' has been untapped in your neck of the woods. They are expensive too - which would mean lots of lovely profit - and all those potential conversions just waiting for the enterprising RV agency.
You mention the use of a generator but they all make a noise which disturbs the peace and quiet of the wilderness.

 

[Averagesupernova]

RVs typically use a gas refrigerator. There is nothing to say you can't use electricity and a heating element to do the same thing, which is what they do. Advantages are they are virtually noiseless, can run on a 20 lb propane cylinder for months, they can freeze ice-cream hard as a rock, etc. I don't see how a compressor type fridge can be better than a gas fridge in an RV. My parents replaced the gas type with a compressor type in their RV because going back to a gas type was just too much money for the amount that they use it. They will admit with no hesitation that the gas type is far superior for the application.

 

[sophiecentaur]

That makes a lot of sense for the RV application. There is, however, a serious problem using gas on boats. Being 'heavier than air ', as they say, it can gather in the bilges and there is nothing to shift it. Even an automatic bilge pump can spark and blow up a moored boat. Gas is used for cooking quite often but it is (or should be) turned off at the cylinder when not being used. A fridge would need a permanent connection and gas really couldn't be risked for long periods.
I'm surprised that your parents found a compressor fridge inferior to a compressor type; absorption fridges in the home have notoriously poor performance figures compared with (mains) compressor types. The thermodynamics of the system is horrific so it figures they should be worse.
But, if a propane bottle lasts for months then it clearly suits many users.