Electrical The hare and the tortoise race _ Compressor fridge verses 3 way gas absorption

Boots in Action

Well-Known Member
Mar 13, 2017
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Ferny Grove, Queensland
#1
There has been a lot of chat about the virtues of both types lately and just a week ago I had the perfect opportunity to see both sides of the story. Here is that story:
Camped off grid in Connondale Ranges from Monday 29th January to Monday 5th February.
Monday sunny and temp around 31 C in the shade. My gas fridge working hard notwithstanding the extra mods fitted. Campers with compressor fridges boasting that their warm beer will be cold by drinking time (dusk?). Good solar power weather. I produced 37ah. Most of the others were using only one panel but still getting good charging.
Tuesday more of the same but hotter - around 33 C. My fridge working even harder and now slowly getting warmer - beer not as cold but all perishables still okay. Compressor fridge owners still laughing and enjoying colder beer etc but also using more power. Good solar charging conditions for all.
Wednesday was a scorcher!!! When we got back at 1.30pm from a quick trip to Brisbane to attend a funeral, the temp had climbed to 36.8 C in the shade. I had taken in my solar panels for safety early that morning so had no charging until after 2.00pm. My outside gas fridge was really struggling even with mods and inside van fridge just holding at 7 C. Did 3 changes of fan thermostats that afternoon (field modifications possible as used machine screws and no rivets to hold thermos in position) from 45 to 50 to 55 C to stop fans running all the time trying to cool back of fridge. Fortunately had extra battery AGM 75ah with me to help with extra demand. See separate posting on how done. As solar panels had not been out , quickly placed both out (180W and 200W) connected in SERIES to MPPT controller. Initial reading was 19.6A at 29.9 volts (load 2.4A), then dropping to 18.9A after a few minutes before settling at 16.8A when I last looked. By 5.00pm, I had retrieved the batteries from 12.3 volts under load to reach the max charge/absorbe setting of 14.6 volts. Not enough into batteries to reach float status though. But at least I now had power to run my fans to keep fridges within the safe range. Beer still drinkable but not like the compressor fridge owners who were still grinning from ear to ear, but using lots of power to keep fridges going at 4 to 5 amps per hour doing so!!
Thursday, rainy with heavy cloud but around 20C. Solar production hardly possible. I just managed to produce 10ah. Compressor owners zilch!!
Friday, more rain and heavy cloud cover - even poorer for solar production. Temp only 20C. Some compressor fridge owners starting to worry and use tug's engine to produce power for battery/ies??. Me, gas fridge working well and easily keeping my drinks and food cold.
Saturday, more of the same as for Friday. All compressor fridge owners now running tug engines (no generators allowed!) frequently at dawn and through the day and for quite a while just before going to bed. Temp still only varying between 19C at night and 21C during the day under very thick cloud. Coldest February day time temps on record for many places!! Solar production virtually nil and my own batteries getting down to 12.2 volts under load too. BUT GAS FRIDGES WORKING WELL AND MY BEER NICE AND COLD.
Sunday dawned cloudy with occasional showers and most campers had given it away and packed up. Temp only reached 23C but at least I was able to get some power into my system. Compressor fridge campers (those that stayed to the end) had been running their tugs into town and other areas to charge up vehicle batteries to stay in the game.
Monday was clear and sunny with occasional showers - temp reached 27C. Packed up and went home , still with cold drinks in both gas fridges.

Who won?? Well if you looked at how things panned out, the hares (compressor fridges) bolted out of the gates when conditions were sunny and they had sufficient battery STORAGE power. When the storage (limited or not) got low, they had to slow down and seek alternative power. The tortoise (gas fridge operators) were left well behind when the heat was on, but continued to operate (albeit less than optimum). However, when conditions were "fowl", they came into their own and kept on with no change of power options. I have to admit that without the extra 75ah AGM connected in parallel with the van fridge (120ah AGM), I may have had to go on power rationing myself to maintain the efficiency of my gas fridges. @Drover once said, you can never have too much storage power. The trouble there is where to carry the extra weight?? My next posting will show how I got around that problem. Hope you liked my story. Tech Heads - note output of solar panels with MPPT controller. Best option I have ever made , even at the extra cost!
 

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rags

Active Member
#3
Not quite a Choice scientific analysis, but good anyway. I have both a gas fridge (van) and compressor (car) and understand the benefits and disadvantages of both types of fridges.
For a successful compressor fridge you need battery storage + charge= Cold fridge.Absorption fridge you need fuel + level fridge + low ambient temperature.= cold fridge.
To accurately compare you would need to ensure all necessary operating requirements are provided.
It is a bit like comparing a heat pump hot water heater against a solar heater, they both work but one will out perform the other dependant on use and environment, The old expression apples with apples, just some are Granny Smiths others are Royal Gala or Johnathons, some good for eating others good for cider.
 

Boots in Action

Well-Known Member
Mar 13, 2017
558
589
93
Ferny Grove, Queensland
#5
Not quite a Choice scientific analysis, but good anyway. I have both a gas fridge (van) and compressor (car) and understand the benefits and disadvantages of both types of fridges.
For a successful compressor fridge you need battery storage + charge= Cold fridge.Absorption fridge you need fuel + level fridge + low ambient temperature.= cold fridge.
To accurately compare you would need to ensure all necessary operating requirements are provided.
It is a bit like comparing a heat pump hot water heater against a solar heater, they both work but one will out perform the other dependant on use and environment, The old expression apples with apples, just some are Granny Smiths others are Royal Gala or Johnathons, some good for eating others good for cider.
Hi @rags , cannot really disagree with any of your statements. Both types work hard (in amps consumed hourly) and gas trying to remove internal heat (heat absorption) when temps get up there. Levelness is important for gas fridges but easy to achieve usually, and their operation can be improved with mods. Never as good as compressor, but a 9kg gas bottle weighs about 22kg when full and lasts about 14 days for fridge only. And no real need for solar, but it is handy to run fans etc. How many batteries at 30 kg each would you need to keep compressor fridge operating for this time and how and where do you carry all your battery storage , not to mention the weight of charging facilities that have to be used as well!! Very good knowledge of electrical systems/solar operation is essential too to prevent damage to system. You are covering both types with fridge in car, but how long can you let it run without recovering the amp hours consumed by running engine in your tug??

Your last sentence regarding comparing apples is spot on.
 
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Boots in Action

Well-Known Member
Mar 13, 2017
558
589
93
Ferny Grove, Queensland
#6
Thats why I like my 3 way but keep my beer in my old Engel...............I have an on/off switch for my fans but use a 70deg thermo as they just keep running all the time on anything lower.
Hi @Drover , covering all bases with both types is a great way to go. Your van fridge is much bigger than my tiny 91L, and I guess has more heat to get rid of. Or perhaps the flow of air is shorter for mine. I started using the 45C thermo as I wanted the fan to come on earlier rather than later, and not be on for long periods. It was quite suitable up to ambient temps of 30C, but over that, I had to resort to a 55C to have it work intermittently instead of all the time. I carry thermos from 40C to 60C in my spare parts box to cover all contingencies. Like you, I have an in-line switch to over-ride thermo for fans as necessary.
 

Boots in Action

Well-Known Member
Mar 13, 2017
558
589
93
Ferny Grove, Queensland
#9
This is why I have 400ah of battery power in my Van
I would have still been grinning with my 3deg drink.
With THAT sort of storage reserve, @NoWorries is "no worries" and pretty correct. Working on an average 4A draw per hour for 40% of time works out at just over 38ah per day multiplied by 4 days amounts to 154ah approx. And providing you started off with full charge in your battery bank, you are not even down to the 50% danger level for maintaining full battery recovery at a later time. Would be unlucky not to get SOME solar power in any later than 4 days! Assuming 4 X 100ah batteries at 30kg each is a lot of weight (total 120kg) added to the GMV of your van. For a lot of us, that would be beyond the carrying capacity not to mention the cost. But if you are able to do that, great!! You will be still be well ahead of the game. I too prefer my beer to be at 3C rather than 6C or 7C in really hot weather.
 

Drover

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Nov 7, 2013
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#11
Well no matter what it's far better than 40 yrs ago when you drank the beer first before the ice in the proper tin Esky thawed out, then you started on the goons which were kept cool in the creek, this also meant the steaks and bangers were eaten in about 2 days then you moved onto the canned tucker if the shooting or fishing wasn't much chop..............Makes me appreciate my van with fridge, shower, thunderater and hot water, not to mention a mattress.
 

Drover

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Nov 7, 2013
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Cooloola Coast, QLD
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#12
I found a pic of the fridge way back when, a bag of of ice and couple of six packs, bag of snags and that was it FULL..................then we upgraded to plastic ones, so much better they didn't leave rust marks on Mum's lino.....I still have a plastic one from way back then it stores cordage now......

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.............The bit near the handle hinge is a bottle opener, no twist tops then and a can spanner was always on the key ring.........................ooppss sorry @Boots in Action , wandering again...................
 
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Boots in Action

Well-Known Member
Mar 13, 2017
558
589
93
Ferny Grove, Queensland
#13
Well no matter what it's far better than 40 yrs ago when you drank the beer first before the ice in the proper tin Esky thawed out, then you started on the goons which were kept cool in the creek, this also meant the steaks and bangers were eaten in about 2 days then you moved onto the canned tucker if the shooting or fishing wasn't much chop..............Makes me appreciate my van with fridge, shower, thunderater and hot water, not to mention a mattress.
Yeah @Drover , they were THE days when one's love of beer (no matter what the temperature!!) and the life in the great outdoors transcended all the rough living we would not put up with now! We were younger then and could take it. We have grown soft in our older years and need a few more comforts, so we can live easier - and longer.
 

Boots in Action

Well-Known Member
Mar 13, 2017
558
589
93
Ferny Grove, Queensland
#14
2 x 200ah batteries but I run a 250lt compressor fridge and a 40lt engel on freezer so I sometimes find myself pull starting the Gennie.
yep 124kg to be precise, but the fridge was about 20kg lighter
Hi @NoWorries , you work on a big scale for everything. Honestly, how long do you really think you would have lasted in those conditions without "rationing" your power and NOT being able to start the Gennie? I am sure that keeping the beer cold would be top of the list for priority power use. So to save all the perishable food stuffs, you then cut out the freezer and eat in the dark??