12 volt fridge on a solar setup

[grubstake]

12V fridges are pretty much as originally designed whereas 240V fridges are undergoing continuous improvement to meet star rating / efficiency regulations.
Note Samsung's claim of a 40% improvement in efficiency over a compressor

Making technical claims is a hallmark of Samsung's sales pitch for everything they sell. Providing zero evidence to support those claims is also a familiar hallmark of Samsung. :N:

Your negative statement about 12V fridge designs doesn't appear to be well-founded:

 

[grubstake]

Mate I can see what you are saying but are you mixing the two inverters up??

An inverter fridge uses a variable speed compressor, that somewhat runs at varying speeds to accommodate the set temperature.
As opposed to a conventional compressor that over its temperature thermostat range, simply 'thumps' on and off.

A 12v DC to 240 VAC voltage inverter, generally, are hugely inefficient.

So are the benefits of an inverter compressor used with a voltage inverter largely lost?

I haven't researched if there is a 12v DC inverter compressor fridge..... there would be massive energy savings there eh?!

The swing compressor in Engel fridges actually runs on 15V AC!

 

[Simmo]

The swing compressor in Engel fridges actually runs on 15V AC!

But its a clunker, not a variable speed eh?

 

[Simmo]

Found a good info site??
https://t1lithium.com.au/using-a-240v-fridge-in-an-rv.html

 

[Jaros]

I've had my Engel running 24hrs a day for 5yrs. Not a hiccup it's 14 yrs old . I shouldn't say that after losing a Microwave and a dishwasher last week.

 

[condor22]

My Engel is a 1992 model bought new. It draws 3.1 A on start up when the fridge is not cold. Normal operating current measured with a number of different ammeters hovers between 2.8 and 3.0 amps depending on the voltage. If under charge at 14+ VDC it is around 2.8 A. When the battery is around 12.7 V not charged and under load, the Engel draws 3.0 A

Below is a screenshot of the Engel Service Manual for the model I own. It shows that it has an inverter that converts 12 VDC to 19 VAC (Also a power supply transformer that reduces 240 VAC accordingly.) As an added piece of info it also gives the material type re insulation and internal cabinet.

I managed to source the Service Manual and full parts breakdown manual, when I was replacing the switch a couple of years ago. Thanks to the Engel rep in Murray Bridge S.A. for that assist. They both have a helluva lot more detail/info than the operation manual we get with the fridge.

 

[condor22]

As you can see the power spec is 33 watts. Divide by 12 V its 2.75 amps, divide by 14.4 V it's nearer 2.5 A. However all inverters have an efficiency loss, hence the difference in actual amps used.

But compared to the Bunnings "fridge" at 72 watts, less than half the power for the Engel compressor.

 

[Nightjar]

Bought new, my 1983, 39L Engel "Old Yella", still purring and still looks like new when the home made insulated cover is removed. By increasing the lid insulation with some sheep skin seat cover the same setting reduced the temperature 4C.
We use it as a feezer on our month long trips away.
Combined with an Engel combo they are both mounted on the back of the ute (under canopy). They are connected to a 100ah agm which is charged by alternator while mobile and solar when stationary.
Faultless running for many years.
Engel gets my vote for the most reliable.
Always run them on 12v while away from the grid, never run them on 240v from a genny.

 

[Ridge Runner]

Many caravanners have switched to 240V inverter fridges run, via a suitably matched inverter, from 12V and are reporting good results.
One of the issues with the Glacio fridges is the poor insulation fitted, leading to higher average current draw.

The down side to that is coming from 12v up to 240 via an inverter it will use a lot more power, If it has the 12v feature then it is best to use it on 12v. :Y:

The people running these conversions, utilising a well matched soft start inverter, claim to reduce overall power usage, cost and increase storage space.
12V fridges are pretty much as originally designed whereas 240V fridges are undergoing continuous improvement to meet star rating / efficiency regulations. Remember, if an inverter is running at peak efficiency, there is usually 10% or less efficiency loss.
Taking that into account, along with the benefits above, the total power usage is actually reduced.

https://www.samsung.com/au/support/...ages-of-having-a-digital-inverter-compressor/

Note Samsung's claim of a 40% improvement in efficiency over a compressor

I am sure Condor can help explain this a little more in depth "fingers crossed" but in simple terms it goes like this,

Regardless whether any thing is plugged in to an inverter or not it is going to draw between 0.150Ah to about 2.5Ah depending on the size or wattage it is rated for regardless and as you draw power from it the Ah number rocket, With nothing connected Say it darws 0.380ah it's going to do that for 24 hours a day 24/7/365, So at 0.380 X 24hrs = 9.12Ah X by 7 days that = 63.84Ah per week X by 52 = 3319.68Ah per year,

With that in mind no matter how long you have it turned On the Ah it draws has to be added to the power used by the fridge,

IE ( Made Up Figures ) Imagine we just bought a new Engel and it uses 16Ah per 24hrs on DC, On AC it draws 230w per 24hrs.

Not many products have a perfect power/draw ratio but the closer to 1 to 1 the better because it means that power is not being wasted, Running on AC On average most nearly every fridge ever made has a ratio of about .51 to .60 which means they are wasting .49 to .40 of the power they draw,

Going back to our Imaginary Engel figures It's using 230w per 24 hours you are drawing that from a 12v source then thats 17.96875Ah @ 12.8v NOTE the actual convertion is a lot higher The you add the AH drawn by our Inverter Above @ 0.380/9.12Ah + 17.96875Ah Our Engel is now Chewing 27.08875 Ah per day, thats a big leap from our normal 16Ah on 12v, On top of that 27Ah you then have to add the power wasted buy the Inverter because they have about a 1.4 to around 2.0 ratio where they require/Waste between 20 and 50% of they are drawing,

Note all I have done is convert one set of numbers as in simple Maths the actual convertion numbers are alot higher because I have not included the "Power Factors" involved. which is where the big differance lies and that is why None of us here will run a fridge on 240v while bush because even that 9.12Ah the inverter uses per day is valuable power and hard to replace over the coarse of a week or more.

Condor can explain it better as to how the Maths works ect. :Y:

 

[Nightjar]

A bit of info from 2020.

https://www.prospectingaustralia.com/forum/viewtopic.php?id=35573

 

[condor22]

I covered inverters in my Bush Power thread. The simple calculation is that most Inverters use approx 10% more power than they produce.

Real world measurements from my past use - A 300W inverter fully loaded you divide by 12 = 25 A off the battery. The actual use was 28 amps due to that 10% inefficiency, which is slightly more than 10%.

The next thing to consider is voltage. When my AGM was fully charged no load and rested it showed 12.9 V. Running the inverter with a 240 VAC TV, 240 VAC Satellite Box and a phone charger used most of that 300 W and from memory the ammeter showed around 24 amps @ 12 VDC. The battery voltage under that load went down to 12.1 V.
This becomes a "catch 22" event in that the lower the voltage the higher the amps as the wattage power use remains reasonably constant.

Bottom line, you're not gonna watch much TV with that kind of load from a battery bank.

In terms of an Engel - Why would you invert 240 VAC from a 12 VDC battery to power it from 240 V. then transform it back down to 19 VAC? The norm would be give the fridge 12 VDC, let the internal inverter provide the 19 VAC as it is far more efficient and only one change compared to two. The answer is only if there is a problem within the fridge itself with the 12 V system as a temporary measure until a fix is available.

More....

 

[condor22]

I have bought a new Engel. Got the dual zone 40 lt, but have not used it yet. Why? lol, I'm changing everything in the next few months.

The 4x4 is going to my Son complete with the old Engel, drawers, battery and solar system as a gift. I've ordered a new 4by but 6-9 mth delivery, maybe.
My van is already in the van dealer's yard as a trade in, minus the Lithium and 12 V TV as they were fairly new. The new van is also in the yard, but I can't have it until after the Feb 2022 Caravan Show here in S.A. The new van has no TV and one x 100 AGM. BTW, if I ordered a new van build the delivery is March 2024 at the moment.

I'll be replacing the 1 x AGM with 2 x 100 AH Pylontech Lithiums as it has a 110 lt compressor fridge unlike the 3 way in the old van. It also has a 30lt compressor Drawer fridge accessed externally.

The Engel 40 lt Combi will go in the new 4x4, so not had chance to test yet, but as I have the single 100AH Pylontech I will test it for power use during a few days of hot weather and again when it cools down.

 

[Simmo]

Wow Condor22!! I'm seeing $150k+ there!!
It will be awesome to work with new 'toys'!

 

[condor22]

Not quite Simmo, trade in lol, but still a bit over $100k. Gotta spend some money as we lost about 2/3 of our pensions due to our recent house sale/move. I can't wait, but will have to, lol.

If the van and car don't turn up in time for my April trip to the GT, I've already looked at a motel for a couple of weeks to quench the prospecting thirst, lol.

 

[condor22]

There's an old saying ............

The only difference between a Man and a Boy, is the price of their toys.

 

[condor22]

I wasn't sure where to put this post, but it might help the author of the post.

Tested the new Engel 39lt Combi (MT45F-G4CD-V) over two days. Battery is the LiFePo4 Pylontech Lithium. Tested in a non airconditioned room of the house.

Notes:-
1. The fridge was completely empty, which tends to be worst case scenario as food/drink bulk help with stored temperature.
2. The set temperature was stabilised on 240 VAC before switching to battery for each test.
3. The battery was charged back to 100% after each test.
4. Power meters and temp gauge all reset between each test.

I did not test to max cold (-18) as 2 tests at minus 5 & 10 are close enough for me. Nor did I measure fridge compartment temp continuously. I did an initial check at the -5 setting and it showed 1.7C to 2.1C over 30 minutes and without content, not realistic.

Results:-

Conclusions:-
1. After 24 hours and under load, the Lithium is still holding above 13 V which, for me, is a huge bonus. Given the testing, I will turn the Low Battery function of the Engel off.

2. The actual temperature of the freezer was held at or below the set temperature in both tests and up to approx 3 degrees C colder.

3. Given this result I think that as a freezer, especially as most of my use when prospecting is in winter, a setting of -8 is what I will use. This will achieve a range of -8 to -11 C.

4. Averaging AH from the 2 tests should give approx 30 AH when set to -8 C.

5. Most fridge specs give power use at around 25 C ambient. My tests were an average of around 23 C, again close enough for me.

6. In the colder winter months of Victoria, I would expect a slightly lower power consumption. Conversely, much more on days of high 30s C to 40 plus.

7. Super impressed with the Lithium holding voltage and should get close to 3 days before a charge is needed. But for cycle life, not gonna happen and charged every day.

 

[woomera]

I wasn't sure where to put this post, but it might help the author of the post.

Tested the new Engel 39lt Combi (MT45F-G4CD-V) over two days. Battery is the LiFePo4 Pylontech Lithium. Tested in a non airconditioned room of the house.

Notes:-
1. The fridge was completely empty, which tends to be worst case scenario as food/drink bulk help with stored temperature.
2. The set temperature was stabilised on 240 VAC before switching to battery for each test.
3. The battery was charged back to 100% after each test.
4. Power meters and temp gauge all reset between each test.

I did not test to max cold (-18) as 2 tests at minus 5 & 10 are close enough for me. Nor did I measure fridge compartment temp continuously. I did an initial check at the -5 setting and it showed 1.7C to 2.1C over 30 minutes and without content, not realistic.

Results:-
https://www.prospectingaustralia.com/forum/img/member-images/1932/1639656934_engel_test.jpg

Conclusions:-
1. After 24 hours and under load, the Lithium is still holding above 13 V which, for me, is a huge bonus. Given the testing, I will turn the Low Battery function of the Engel off.

2. The actual temperature of the freezer was held at or below the set temperature in both tests and up to approx 3 degrees C colder.

3. Given this result I think that as a freezer, especially as most of my use when prospecting is in winter, a setting of -8 is what I will use. This will achieve a range of -8 to -11 C.

4. Averaging AH from the 2 tests should give approx 30 AH when set to -8 C.

5. Most fridge specs give power use at around 25 C ambient. My tests were an average of around 23 C, again close enough for me.

6. In the colder winter months of Victoria, I would expect a slightly lower power consumption. Conversely, much more on days of high 30s C to 40 plus.

7. Super impressed with the Lithium holding voltage and should get close to 3 days before a charge is needed. But for cycle life, not gonna happen and charged every day.

https://www.prospectingaustralia.com/forum/doc/member-docs/6207/1639659214_engel_mt45f_performance_curve.pdf

 

[brendomac]

Thanks condor (and everybody else) , very interesting indeed. That is a pretty good result for ah draw over 24 hours.

Needless to say, thanks to everybody's advice, I skipped buying the bunnings fridge. But part of my research ended up going down the rabbit hole of solar panels in parallel versus series. Honestly I had no idea that they would work differently.

Anyway, I'll keep looking for fridges. This weekend will be a combo of my car Engel and a good old fashioned techni ice esky.

 

[condor22]

You're welcome B'Mac.

Woomera, Thanks for the chart you posted. The chart is for a single cabinet 40lt Engel, not the Combi, I would use it as a guide, as it's similar. Unfortunately the Engel chart does not state if their tests were done on 240 VAC in a Lab or 12 VDC battery, or what type of battery, or if loaded with food. All of those criteria can affect performance. Lab tests are "clinical", under controlled conditions, but when we use things out bush there's little control, lol.

However, after doing some food safety Googling, I have learned that some frozen food can still grow bacteria at temperatures above -15 C. As a result, I am going to run a power test at -15 on Sunday. Gonna be very hot here today, but Sunday's weather forecast is similar to my first two tests to keep a common ambient.

One result not posted - I noticed a max amps reading of 5.2 A and realised this was the "turn on" spike when I switched from 240VAC to 12VDC. I did look at the meter on a couple of occasions and noted that when the fridge cycled on, it drew around 3.2 amps, but after a couple of minutes settled to around 2.95 to 3.0 amps. As my power meter is inline, it will pick up this spike.

During my working life, I have done lab testing on washing machines, household fridges and specialised for several years on house to commercial sized evap aircon. I did a number of tests in new school facilities after aircon install, so I know there can be difference between lab and real world testing.

 

[user 22230]

Tests, current draw battery capacity is all well. Most important item IMHO, is a quality controller for solar panels such as a Victron. Quality controller along with moving panels thru out the day will give max return for daylight hours. Many controllers supplied with panels can be brought for about $4.50 on Amazon and not even MPPT as claimed. :awful: