Realistic usage from 4.5 amp 12 volt frig ?

[DavidGraves]

Howdy

I don't have an electrical engineering degree ( did not want one ).

I was given an older small Norcold 12 volt frig that draws 4.5 amps.

This is the same draw as many of the newer portable frigs.

How long could I realistically expect it to run before drawing down my single AGM house battery ?

No other 12 volt draw and 70-80 degrees F ambient.

Many thanks for the simple answer.

DavidGraves

 

[Bill D]

75 Ah (average battery)
/ 2 = 37.5 Ah (because you don't want to run them below 50% capacity)
/ 4.5A
= 8.3 hrs (if the fridge was running full time)

I would also use a computer fan to vent hot air to the outside. This will of course use power, but less power than having to run the fridge more often.

Of course there are a lot of variables.
-ambient temp
-was the fridge and food prechilled
-how much food is in it
-how efficient is it

One thing I like to do to increase efficiency is put frozen icepacks in the freezer compartment the night before a trip and load up some cold beverages as well. Then I plug the fridge in the night before a trip. This gives me a nice head start on keeping things cool.

Realistic usage is a tough number to come up with. I'll leave that for others who have run tests, as I have not. My guess would be 1/3 efficient, so 24 hrs max.

 

[Vic Harder]

Assuming your house battery is around 80 AH, and 50% of that is usable (to avoid early battery death) you have 40AH. Call it 45 to make the math easy. 45AH/4.5A = 10 Hours

Plus what Bill D said

 

[Beach]

X2 the above replies.

 

[JaSAn]

Howdy

I don't have an electrical engineering degree ( did not want one ).

I was given an older small Norcold 12 volt frig that draws 4.5 amps.

This is the same draw as many of the newer portable frigs.

How long could I realistically expect it to run before drawing down my single AGM house battery ?

No other 12 volt draw and 70-80 degrees F ambient.

Many thanks for the simple answer.

DavidGraves

I have an older (1982) Norcold DE-251D 12/110 volt refrigerator in my camper. It is surrounded by 3 inches of isopoly on the sides, top, and bottom, and has 36 sq. in. of forced circulation in back around the condenser. With a full refrigerator and 70º to 80º temps, it runs about 30% of the time. At 95º it runs ~50%of the time.

So with Bill D's numbers for full time running = 8.3 hrs -> 30% duty cycle = ~ 25 hours.

Most critical thing to reduce run time is enough circulation in back to get rid of the waste heat. Second is keeping the refrigerator full (I fill any empty spaces with beer ).

jim

 

[rando]

The estimates of a 30% duty cycle at around 75 degrees is pretty accurate in my experience. It also depends a little bit on whether it is a portable/chest type fridge or a built in fridge, and if the coils are vented outside (at 75 ambient) or inside the camper or truck where the temperature tends to be higher than ambient. With a true AGM battery I would be a little more aggressive on my depth of discharge and run it down to 30% SOC which would give 75*0.7/(4.5*0.3) = ~36 hours.

 

[LAWNMOWERMAN]

I also have a Norcold 12volt with a Sawafuji swing compressor and it only draws 2.8 amps.My ARB 50 with a Danfoss compressor draws 5 amps.

 

[JaSAn]

The startup current on mine is ~4 amps, which quickly tapers down to ~ 3a. I paid close attention to the draw the first couple of trips but haven't looked at it since as my system is working well. OP needs to do a little testing on his system if he wants to skirt the limits of his battery.

jim

 

[DavidGraves]

Many thanks for the comments related to the amp draw of this little Norcold.

What I really seek is a compact,( portable would be okay), fridge that would have three way ability to pre cool at home, 12 volt underway and propane in prolonged camp.

The same Chinese company that makes some Dometic portables makes such a cooler, marketed by Candian Tire.

We bought just such a MobiCool last summer in BC.

It seemed a perfect match but failed to cool in an overnight, out of the box propane test.

Darn shame, this unit would perfectly serve our needs.

Reviews of the MobiCool reveals lot of mix results....often lots of exchanges for a new unit which then serves well.

Anyone here have experience with the MobiCool three way fridge?.

Many thanks

DavidGraves

 

[RC Pilot Jim]

David, my 2 cents

A top loading portable is more efficient because the cold doesn't fall out when the door is opened. Our 35 quart Engel MT35 (picture is the 40 quart side opening MR40) holds enough food for two for 7 days. And ice for 7 days (holds ice cubes doesn't make them on fridge mode). We carry a mid-size Igloo ice chest for drinks. We have the small Eagle shell so position the Engle under the front window. Been working great for 3 years now. Average cycling amp draw after cool down (20 minutes from ambient to 39*) = 1.5 amps. Our one 80 amp AGM with 50% usable voltage lasts 20 hours before needing a recharge.

 

[rando]

The 3-way 12v/120v/propane fridges (also called absorption fridges) are horrendously inefficient when run off electricity (they convert it to heat first then use it to drive the absorption cycle), have a limited temperature differential that they can create and tend to be kind of finicky. Most people upgrade from these to 2-way compressor fridges for these reasons.

Many thanks for the comments related to the amp draw of this little Norcold.

What I really seek is a compact,( portable would be okay), fridge that would have three way ability to pre cool at home, 12 volt underway and propane in prolonged camp.

The same Chinese company that makes some Dometic portables makes such a cooler, marketed by Candian Tire.

We bought just such a MobiCool last summer in BC.

It seemed a perfect match but failed to cool in an overnight, out of the box propane test.

Darn shame, this unit would perfectly serve our needs.

Reviews of the MobiCool reveals lot of mix results....often lots of exchanges for a new unit which then serves well.

Anyone here have experience with the MobiCool three way fridge?.

Many thanks

DavidGraves

 

[DavidGraves]

Thanks Rando

Horribly inefficient on on electric does not cramp my style....driving several days to remote destination...efficient on propane for a week outback serves my needs.

Do you know of other chest type three ways than this Mobicool/Dometic orphan ?
Many thanks

DavidGraves

 

[CamperCamper]

Put in one solar panel with a 2-way compressor fridge and fuhgettaboutit.

 

[nikonron]

^ X2 Exactly!