Comparison of Best Portable 4x4 Fridges (Feedback Request)

Hi Pete,

I would have thought that AmpHrs would be the most appropriate number as most people would be using this number to determine the capacity of the battery they will need. As you know capacity is measured in AmpHrs, not Watt Hours. Just my thoughts.

Macca.

"AmpHrs" is certainly in common usage in the RV industry Macca, but no where else, and it is generally assumed to be at 12V. Problem is, things are changing like never before.
If you buy a battery for your house solar system, it is rated at kWh (along with the solar) and many of us are going Lithium in our RVs with a nominal 12.8V (or maybe higher) instead of 12V.
So the value of an "Ahr" can not be safely assumed any more.

What prompted my post however was that some of the values looked like they might have been Amps draw rather than Ahrs consumption. For similar reasons to above, Watts takes away any possible confusion and equally applies to the 240V fridges (and other appliances) that many are running via inverters in their RVs. Those inverters quote power capability in Watts, not Amps.

The OP has produced a great body of work (and he did ask for feedback). My post was intended to be constructive. :)
Cheers,
Peter
OKA196 motorhome

ps... as I said in my post, getting reliable energy consumption information will be problematic. The power (Amps - watts) number is likely to be more accurate, but it is the energy (Ahrs - Watt hours) number that is harder to establish because it can be so variable. It is also the only number that is really important which makes it quite a challenge.

.
Peter is quite right in all he has said above. The correct way to define the instantaneous power is in Watts which takes care of voltage variation.
Even then, when describing the usage of an appliance such as a fridge it only has information value if the usage (Watts) is incorporated with a definition of the period that this consumption took place, say "per hour" or "per day". A better expression is to define the consumption in 'Watt hours' (Wh) which then clearly defines just how much energy the appliance consumes in use.

There is no reason for us to not use the correct terms of "Watts" and "Watt hours" . But good luck in getting that accepted in common usage. The auto industry abounds with imprecise definitions.

We also see confusion between the terms "power" (watts or 'Amps @ 12V') and "energy" (Watt hours or Amp hours @ 12V). I have to think twice each time I use the terms and I often mix up power and energy.
I think it is a legal requirement for AC appliances to state the input power requirement on their compliance plate. I have looked at a few of the fridge specs and it is often just missing.

And "Amps" is neither power nor energy, notwithstanding batteries being commonly described as "100 Amps".

As an extra complication, the Secop/Danfoss compressors are variable speed (others may be too), so the input watts can vary depending on the speed that it is set to run at. That variation in speed also effects the efficiency of the compressor. Provided it is producing sufficient cooling, the slower the compressor is set to run at (and the longer the duty cycle), the less total energy it will use.
There is an expensive accessory that automatically adjusts the compressor speed to maximise the duty cycle, while maintaining sufficient cooling for the use and temperatures, that minimises the total energy consumed. Very clever, but excy.

It is a complicated subject and full of compromises. The OP's chart is a very valuable tool, especially so if the electrical comparison is legit.
Cheers,
Peter
OKA196 motorhome

.
Don't worry Peter, although I have been doing it for a lot of years, I also hesitate when assigning "power" or "energy" to consider that I have chosen the correct one…… and still may occasionally get it wrong if I am being inattentive.

When an appliance is constructed to run at variable power levels it is usual (and reasonable) to rate it at only the highest level.

Yes, it is a "complicated subject" but I don't know that I would use the term "compromises". Omissions or inexactitudes perhaps?

There are compromises when choosing one product Vs another Allan and what is important to each application determines the choice.
Your "best" fridge might be well down the list for me.
When I built our OKA 20 years ago, minimising energy consumption was important. Solar panels cost $9/watt. I did a DIY freezer because nothing on offer suited my perceived needs at that time. It was small (25L) and had 150mm of quality polyurethane insulation all around and a remote compressor. I also added extra insulation around the fridge which also had a remote compressor that made that easy.
The result was high performance with minimal power.

I am now building a new OKA. Solar is cheap. I will use a 200L+ commercially made fridge/freezer, an inverter and lots of solar.
Cheers,
Peter
OKA196 motorhome

.
Ah, I see what you mean Peter. "compromises" in product choice. Yes, there always is.
I was trying to fit "compromises" into the subject of Watts, Ah, and energy etc.

"We also see confusion between the terms "power" (watts or 'Amps @ 12V') and "energy" (Watt hours or Amp hours @ 12V). I have to think twice each time I use the terms and I often mix up power and energy."

Since we are being pedantic, Amp hours isn't a unit of energy. It's a unit of charge.

Same with the Brass Monkeys, my 50 & 60L are not listed but then there is about 10-12 different sizes.

For a 3.6 amps while running fridge to get to 1.8AH, all it has to do is run for only 1/2 the time in one hour !
Quite feasible to have a fridge run for 10 mins and rest for 10 mins !

Gronk
I agree, but the test conditions the fridges are operated in are not the same conditions the fridges are USED in. In the rear of a wagon or under a metal canopy the ambient will be higher and the run times simply go out the window. Just expect more battery needed.

I would presume the figures in the comparison are from the manifactors and not the opps own test ?

Power consumption seems to have disappeared.

Hi I was surprised when a King saleman told me there frigs have a 5 year replacement warranty if it fails bring it back and we will exchange .

Jaycar & RTM have 3 years on the Brass Monkey, just swap them out for a new one.

It is what it is and your leaving wont change a thing but if you stay you can set a example even if nobody follows it.

It isn't just this forum Troopy, it's the whole country, a couple of generations of people that think they know everything because they can google till they find other pretenders that preach the same misconceptions they do.
For some unknown reason it's human nature to believe what we read, it is how the schools taught us to learn, but now most of the literature is written by retards with more lithium in their system than the electrical systems they are pretending to be experts on.

Bye Troopy

Couldn't stay away hey you only lasted 10 hours it's just an observation after the previous statement.

Well said Leigh. And agreed the table is a great start to help looking for a fridge.

The self appointed experts advocating Wh apparently have little real world experience.

Battery capacity is stated in Ah, and the useful time a fridge can be used is simply the available battery capacity ( Ah) divided by the Ah per day or per hour. Simple. Thats why fridge manufacturers use that unit of measurement.

Using watts or watt-hours complicates the calculation for no benefit since the ( near) constant 12V - close enough for the calsc( given other variables like temp, current draw, battery age, use profile, etc)

That's basic year 8 maths.

.
"That's basic year 8 maths."
Yes, of course it is Tony.

" Perhaps not as prominent now"

Maybe that's because:

1. They were spelt Waeco

2. Dometic have taken them over and rebranded them.