12 volt fridge on a solar setup

[brendomac]

Hi All,

Warning, my head still explodes with 12 volt stuff.

I'm thinking about using a 12v fridge on a solar setup. Specifically this fridge: https://www.bunnings.com.au/glacio-90l-portable-camping-bar-fridge-freezer-12v-24v-240v_p0336461

* The blurb says about 1.7kw for 24 hours of use, so about a 6amp draw. It has a 72 watt compressor.
* The solar panel I have is 175 watt, I can double this by putting two together if needed. For one panel, in good conditions, I am looking at about a 15amp feed.
* It would be attached to a 100ah battery

* The plan is to leave it on permanently on a bush block, rather than turn it on when I arrive. So I can have ice in the freezer and the fridge is cold when I arrive. I'd probably get there every couple of weeks or so.

My concerns are a run of bad weather, stuffing the battery etc. Or maybe it is just a silly idea with the equipment available.

What do you think, is it feasible?

Thanks

 

[user 22230]

Ambient temps will play a big part? Quality of controller and panels being fixed will limit harvest. In FNQ at the moment not feasible. Fridge cut off voltage of 10.2 is to low and will damage an AGM as in dramatically shorten it's life span.

 

[user 12139]

I suppose it depends where your bush block is & how often crappy weather prevails. Maybe go 2 deep cycle batteries in parallel to get a longer draw down that hopefully outlasts the crappy weather

 

[Rodt]

No argument that two batteries are always better but you should be OK with one. As already said weather conditions and ambient temp play a part but if the compressor cycles 50% of the time (used to be the rule of thumb) then you will have enough. This also depends on how often it is being opened and once you have ice in their it will also be more efficient if stored over time. The thing to consider is that having an AGM battery (am assuming this is what you have) cycle down to below 50% charge does shorten their usable life

The key will be to how much charge will be able to get into the battery and that is at the mercy of the weather conditions unfortunately.

 

[brendomac]

yeah, I thought 10.2 was pretty low as well. The location is in the southern tablelands of NSW. So hot summers, cold winters.

The panels will be in the shade from 3:30pm in winter. Although in summer that does not happen.

 

[condor22]

The info on Bunnings web page states a 72W compressor with about 1.7 kWh for 24 hours. However it does not state if that is when on 240VAC or 12VDC. Crucial info as;

1.7kWh/24 hrs at 12 VDC = 71 W per hour or 6.9 AH/hr, which means it is running non stop.
1.7 kWh/24 hrs at 240 VAC = bugger all i.e. around a 1/4 of a W per hour. So I am confident it is a 12 VDC spec.

In terms of a portable 12 VDC fridge this is one of the worst power hungry fridges I've ever seen if these are real world specs.

The specs on my up coming new van - Dometic 110 lt compressor fridge current draw is 6.2 A, but rated 24 hour power use is 360 W or around 30 AH per 24 hours @ 25 C ambient. I'll be running 2 x 100 AH LiFePo4 deep cycles as the van also has a 30lt drawer fridge. Initially, I'm likely only able to give them 220 or so W of solar, so DC-DC and genny charging will likely be needed. The big difference is that when in use, I'm there to manage it. If you are not present all the time, then you definitely need more solar than less.

My minimum spec for a compressor fridge like the one I am getting is 200 AH of battery (AGM preferably Lithium) and 400 Watts of solar. Even then if you have a few continuous days of crap weather, the batteries will be getting really low, without any other charging source.

Remember in fine hot weather, you get more solar and the fridge works harder. In winter fridge works far less and so do the solar panels. You need to figure out worst case and size the system accordingly.

 

[Ridge Runner]

Struth 1.7Kw per 24 hours is Nuts, My household 300L Fridge Freezer only uses 1068w per 24hrs in an ambeint temp of 37/38*c,

Even the Mighty Big SnoMaster could not chew that much power and it was a Pig when it came to power Draw on AC or DC, So much so that it hold the record of all the fridges I have tested when it comes to power draw,

I can't see that fridge chew 1700w in 24 hours, It has to be a mistakes in translation.

 

[Jaros]

Save your money and get an Engel -new or 2nd hand much better appliance.

 

[brendomac]

Thanks all for your feedback. Its super useful info for me. Like I said I'm not too crash hot at 12v.

The main reason i am looking for a traditional front opening fridge is because the family like the idea of it for convenience.

I'm running an Engel in my car and it's great.

Condor, Sounds like I need to do a little more research I wasn't expecting those specs!

 

[Nightjar]

Set it up with the contents you want to have in the fridge for your bush camp. (Don't open it during this time.) Run it at home for a few weeks trial, this is a sure/positive way of seeing practical results.
Have never been one to trust equations/specs.

 

[grubstake]

Thanks all for your feedback. Its super useful info for me. Like I said I'm not too crash hot at 12v.

The main reason i am looking for a traditional front opening fridge is because the family like the idea of it for convenience.
I'm running an Engel in my car and it's great.

Engel make front-opening fridges too:

https://www.engelaustralia.com.au/product-category/products/upright-fridge-and-freezers/

 

[Ridge Runner]

Set it up with the contents you want to have in the fridge for your bush camp. (Don't open it during this time.) Run it at home for a few weeks trial, this is a sure/positive way of seeing practical results.
Have never been one to trust equations/specs.

Thats right they never match, A lot of the time real world testing the facts "can" be 20-35% better, Not very often they are worse.

 

[RM Outback]

Save your money and get an Engel -new or 2nd hand much better appliance.

X2 you won't be disappointed buying a tried and trusted quality product erfect: in the long run you will save money.

 

[Simmo]

There is lots of good gear out there eh?!
Check this thing out..

https://www.mygenerator.com.au/dometic-waeco-coolmatic-crx140-fridge-freezer-135l.html

 

[brendomac]

Wow, so that massive Dometic only uses 1.2A and the Engel only 2.5A. That is so much lower than the 6a that the bunnings fridge draws.

 

[bicter]

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.

 

[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:

 

[condor22]

The key things with any fridge;

1. Current draw is a subjective value. i.e. an Engel chest fridge draws just under 3 amps, a Waeco can draw up to 7 amps. That's when the compressor is running. The key factor is how much it uses over a 24 hour period. The thermostat bandwidth of temperature is different fridge to fridge. By that I mean if you set to 2 C, the compressor might restart at 4C in some fridges, 6 C and in others different values again. I know my 30lt Engel cycles more often than my 15lt Brass Monkey, but over 24 hours uses less AH for twice the size.

2. Insulation - If the ambient temp is high and the fridge is not as well insulated, the temp rises quicker and the compressor has to work harder. Most fridges use rigid polyurethane (PU) foam, some use polyethylene, the latter is stronger but more expensive. Then it can depend on material density etc etc.

3. How often you open them. A chest type fridge will lose far less "cold" than a vertical fridge when opened.

Said many times by many people. "You get what you pay for".

 

[bicter]

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

 

[Simmo]

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?!