12V / 24V DC Fridge / Freezer Unique 290L (10.3cuft) Review

[Dacian Todea]

I got a large (for me at least) DC fridge/freezer about 3 days ago so I decided to write a short review for others that may be interested.

It was fairly expensive especially for what it is but this DC fridges are still a very low volume business.  The quality is about the same with lowest cost AC equivalents at 4 to 5x the cost.

In total it was about 2099CAD but including taxes and shipping 2427CAD purchased online from Home Depot and shipping cost (Shipping was just 91CAD).

It had two small dents and small scratches (don't care much about that) but for the price you expect better. Was likely opened before maybe even store display but hard to say.

Before this I had one and then more recently two basically free at 99CAD https://www.walmart.ca/en/ip/coleman-powerchill-40-quart-thermoelectric-cooler/6000196317758?skuId=6000196317759 

And this was run at 5 to 6V 10 to 12W continues for the past few years and could maintain about 15C to 17C below ambient (good enough for my fairly constant temperature house).

That means one of those was using 288Wh/day but recently I had two of them.

My wife wanted a freezer so if I was going to go there it was best to get a combo fridge freezer so I only use one device.

This Unique 290 liter capacity fridge freezer https://uniqueappliances.com/product/unique-10-3-cu-ft-solar-powered-dc-fridge/ has the fridge volume alone 6x higher than one of the small fridges I had and the freezer is also about 50% larger than one of those small fridges. But even so 7.5 of those will have costed a third of what this one costs :)

I was considering an AC fridge / freezer as there are way more options and much lower cost but that requires a small efficient inverter.

The main reason I decided in the end to go for this one was the fact that there are no pipes or fans inside the fridge or freezer and all the AC version I seen had pipes inside and most also at least one fan and I do not like those because of the sanitation problem. By that I mean there are parts where batteries or other stuff grow and and not be cleaned or at leas not convenient.

The reason they need the pipes and fans inside is not just so temperature is more uniform but it can cool much faster as they have a higher power compressor.

The second reason was that most if not all new fridges for aesthetic reason likely have the condenser inside the fridge under the case most (hard to say) on bot sides instead of at the back.  This one is much more classic and has the serpentine pipe at the back painted black made from copper plated steel.

This allows me to modify it whenever the compressor will fail as it will probably be peltier based again. Hopefully it will last at least 5 to 10 years.

And also it allows me to add extra insulation on the outside increasing the efficiency significantly.

There are two parts to a fridge efficiency. One is the insulation as you need to cover the loss and the other is the compressor less important as most are fairly low COP at least what it can be found in North America where the internal volume of the fridge is top choice for consumer and efficiency is probably around last if it is even a criteria.

Now about the performance that most of you are probably interested in.

This is the link to the compressor spec https://selector.secop.com/fileadmin/user_upload/SEPS/datasheets/bd80cn_101z0403_r290_12-24vdc_12-2020_desd100r702.pdf

It uses R290 refrigerant so basically very clean propane about 120g of it so not much (a cigarette lighter has maybe 5g so about 24 of those).

The COP is not great but that is typical for these small compressors maybe 1.4 to 1.5 in the region that it is used still much better than peltier around 1 when used at low power but peltier at that COP can do just 15 to 20C delta where this can do easy 40 to 50C delta at better COP so fridge is OK with peltier but freezer is almost impossible unless you want to sacrifice efficiency significantly and probably having two or three stages.

The spec was also useful as it showed max input voltage of 31.5V so I feel good connecting directly to battery no DC-DC conversion needed and I tested at both 12V and 24V with 12V slightly more efficient but not so much that adding your DC-DC converter will make any sense maybe 5% less at 12V

Here is the photo of the SBMS120 4h graph I took this morning with mostly the fridge running so you can see the duty cycle and I can calculate the consumption.

 Average time the compressor is ON about 11.5 minutes and average off time 17 minutes. Fridge is set at level 5 of 7 with 7 being the coldest but that means below freezing in the fridge.

This settings seems to result in about +3.6C in the fridge (tested with a thermometer probe that sits in a plastic container filled with water).

Of course it takes about 24h for the temperature to get there and if you add some room temperature items in the fridge it my increase back above 4C depending on what else it is in the fridge that can acct as thermal storage.

So average power the compressor requires is starting around 70W (soft start over about 30 seconds) then slightly over those 11 to 12 minutes drops to around 60W

A cycle is about 28.5 minutes so 11.5/28.5 = 40% and off time around 60%

Then with average power during on of 65W x 40% = 26W average power usage over 24h that adds to 624Wh so not that bad just slightly more than my two much smaller peltier fridges.

This will translate in to 227kWh/year so way more than comparable European standards but quite a bit better than cheap AC fridges. The more efficient AC fridges may actually be around the same but when you add the inverter is likely the same or worse.

Above graph shows the soft start sequence with the 30 seconds slow power rise (rise is about 10 seconds here and then another 20 seconds starting at lower power likely lower RPM setting) then jumps to full power and remains there.

Absolutely no problem for my house DC outlets connected with 12AWG wires and 16A breakers.

Below a few photos of the fridge inside. I took this before installing it.

Fridge simple mechanical thermostat with no fans or opening the top back of the wall will cool and some ice/snow will create there.

 Freezer is about 60 liters and the back and top side get cooled. Inside freezer temperature is dependent about fridge setting but as it is averages -14.5C with fluctuations between -13C and -16C  (measured air temperature in the middle of an empty freezer).

 

 

It has 4 glass shelves one of them less deep the one on the bottom above the blue box. 

[J.W van de Poll]

Great review.

By the way, I bought a small digital thermometer and display to control the Freezer separately

to stay within -16 to -19 C.  By turning the fridge control to maximum,  allows the freezer control to

control the cycling. The fridge is now secondary but still seems to keep to below 7C.

Has been operational for 7 years now.

Regards

[Dacian Todea]

I do not need to control the freezer temperature. The fridge temperature is much more important while freezer just needs to be below freezing and -14.5C is adequate.

Fridge is usually the important one to control and want to always stay above freezing +1C and below around +4C

[C G]

I had their 13L fridge (UGP-370L1) for a short period.  Unfortunately, mine was defective and they weren't willing to repair it without it being returned and me waiting a long time for a replacement to ship.  Mine got to where it was never turning off and the fridge was too warm with things going bad.  They thought maybe it was a microleak in the refrigerant.  Since I was going to have to wait a long time for a replacement anyways, I just ordered their larger 16.6L model (UGP-470L1) to replace it.  Home Depot messed up and didn't actually get it ordered - it turned into a bad experience and I just gave up on it and got a free AC fridge instead.

This 13L model is not 24V from my understanding - it uses a 12V compressor and uses a small DC converter when 24V input is detected.  The larger 16.6L model that had wire shelves inside instead of glass, and used a larger native 24V compressor.  Sadly, it appears they have discontinued that model.  The Unique 16.6L model was the only fridge I could ever find by any brand that used a 24V compressor, and that would have been interesting as I imagine it should be a little more efficient to run at 24V than by using a 12V converter.

[Dacian Todea]

Maybe it was not defective. Mine took about 4h of continues run (empty) before fridge started to cool a little bit. During all that period the fridge was just at room temperature.

The compressor power is much lower than on typical fridges so it takes longer to cool initially. Compresor on the 370L model is the same and I can imagine with even large volume it will have needed maybe 6h before starting to cool the fridge amd maybe 12h to get to set temperature and stop.

All DC models (up to 370L not sure I saw a 16.6cuft version 14cuft is max on their website at the moment) use the same compressor and the compressor is DC brush-less basically an AC motor probably 3 phase that are done by included motor controller and that supports 12V and 24V operation up to 31.5V max

Efficiency of this small compressors is not that impressive but it is not bad. Like I will probably not add extra insulation to reduce the consumption as it is small enough as it is and I have no problem with that.