Operating 3-way refrigerator on battery only, but with external fan(s), while towing

Bayliss

QUESTION:  For those who have added external fans to your 3-way refrigerator, can you tell me if that has helped maintain the refrigerator temperature while operating it on battery only, while towing?  I am also interested in forum member thoughts on the pros and cons of switching out my 3-way refrigerator for a more efficient 2-way model, for the reason described below.

I have the originally installed 3-way refrigerator (Norcold N180.3x) in my 2019 320 S Boondock Lite.  Unlike many other T@B owners, I have had no operating issues with it, EXCEPT I have experienced the often-reported problem of it struggling to maintain the proper temperature when the ambient/outside temperature is in the 90s+.  Therefore,  in conjunction with installing a lithium or AGM battery, I am considering either adding dual external fans, OR swapping out my 3-way refrigerator for a 2-way model.

I do not want to operate the refrigerator on propane while towing.  I have operated it on battery (Group 24, lead acid) while towing with my truck, which has a 150-amp alternator that keeps the trailer battery properly charged.  However, even if I start out with a very cold refrigerator, the battery does not help the refrigerator maintain a sufficiently cold temperature while towing in hotter outside temperatures (i.e., the temperature rises significantly.)

I currently intend to upgrade to either a 100 Ah (minimum) lithium, or a 125 Ah AGM battery.  Since I am not having any problems with the 3-way (other than as already described), I am wondering if adding a couple external fans will likely solve the temperature issue (both while camping and towing.)  If so, I don’t feel the urgent need to switch to a 2-way model, particularly since my 3-way is essentially in brand new condition.  Greg)

Grumpy_G

No the fans don't make a difference in this case. The 12V heater is the weakest of the three options in terms of heat output which in turn limits the amount of cooling it can achieve. It is my understanding that the 12V setting is only intended for traveling and can barely keep the temperature on a good day. So the issue is not the amount of heat that can be removed from the fridge, especially when moving which aids in removing air through the vents. 

Now when running on gas or 120V at a campsite, additional fans do help with removing heat from the fridge compartment. 

Denny16

Your best option is to replace the 3-way with the new Isotherm Elegance 65 as a replacement.  It is an AC/DC 2.3 cu ft Danfoss compressor fridge with a small freezer, that would fit in the Norcold cutout space.  Someone here did replace the 3-way with the new 2-way, which keeps food cold and does not draw anywhere the power the 3-way requires.
 Cheers 

Bayliss

@Grumpy_G and Denny16, thank you both for the information you have provided.  Very insightful.

Mickerly

If you are into chasing things, Dometic invented the Ammonia absorption refrigerator in the 20's. Because of the design, it just can't function when the temperature is above about 88F. On the west coast or in the desert Southwest it works OK because it cools off at night and the machine can catch up. In the Midwest and gulf coast not so much. The advantage is not using any battery.

Denny16

Miclerly, Dometic may have had one of the first commercially made absorption fridges, but they did not invent the technology.  The design goes back to the 19th century, and you are correct in that this is a 100+ year old technology, but so are compressor fridges, that were used to convert traditional ice boxes using a compressor to cool a cold plate under/or instead of the ice block  Here is a brief history of absorption fridges:

 “The ammonia refrigeration cooling system which is also known as an absorption cooling system was first discovered in 1824 by Micheal Faraday who tried to liquefy gases which, among them was an ammonia gas. This experiment was used in taking ammonia vapor in a glass tube with silver chloride in it and allowing it to absorb in the silver chloride powder. He then heated the chloride -ammonia mixture and watched the ammonia liquid evaporate out of the silver chloride and become cold. This experiment later was the birth of the ammonia absorption cooling systems [HEREAFTER CALLED PROPANE REFRIGERATORS].

“In 1926 Albert Einstein and a former student, Leo Szilard, embarked on a venture to develop a safer refrigerator since the electric refrigerators of the time were known to leak toxic gases through broken seals. Such an incident of a German family killed by fumes caught the attention of Einstein and sparked this project. Einstein insisted that a better refrigerator design must be possible.

“Their goal was to design a device with no moving parts or mechanical motion and eliminate the wear and tear factor. They used their knowledge of thermodynamics to produce an absorption refrigerator. This device would drive a combination of safer gases and liquids through three interconnected circuits. It required only a small gas flame as a heat source and was totally sealed and safe. Some experts estimate the sealed system could last 100 years.

“Einstein and Szilard applied for and received 45 patents in 6 countries for this type of refrigeration technology.”

Cheers 

Mickerly

The history of some of these inventions is festinating sometimes. It still doesn't make the propane frig work with it's hot out side.  ; ) 

If is stays below 85 they work great without any electricity. Stuffing the top of the propane frig with ice will help in areas that are hot during the day and cool down at night. July and August in Arizona is tough for that design, but workable.

That being said, I like my compressor frig. Texas doesn't cool down at night and AC becomes a necessary for about 5 months. So, I'm not trying to operate on batteries.

Denny16

Good idea, and I agree, modern compressor fridges are a much better choice than trying to use absorption fridges, especially in hot areas.  I love the two way Danfoss compressor fridge in our TaB400.
cheers