Running a 240 volt fridge via an inverter.

Submitted: Tuesday, Oct 29, 2019 at 10:02
ThreadID: 139248 Views:12966 Replies:3 FollowUps:6
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Hi Folks, I haven't been on here in ages, but recently bought an old Cabana Caravan to take the grandchildren camping. Anyway, I thought I'd share this

Running a 240 volt bar fridge from a 12 volt battery via an inverter when off grid. Firstly whilst I don't claim to be Collyn Rivers, I've been around 12 volt camping stuff for years, own a related business and used to fit dual battery systems. Given I had the gear kicking around I put it to the test.

I have an old Varta 100 amp AGM that is a bit tired but not too sick (it will hold 12.75 volts wheras a new fit one will hold 13.0). I ran the fridge (an old 90 litre NEC cheapie that came with the van) on 240 yesterday filled with cold stuff. At 8pm I plugged the fridge into the inverter and ran it overnight. At 8am today the battery (standing voltage) was at 12.2.

I then plugged in the 300 watt solar panel setup and continued running all day via the inverter on a miserable Melbourne day. The sky as you see it in the photo was pretty much how it was all day with regular rain. I shut it all down at 6pm and let the battery settle, it showed 12.42. In effect on a very solar unfriendly day, the solar had run the fridge and inverter, and had "banked" about 20 amps.

Running a 240 volt fridge from 12 volt through an inverter is highly inefficient compared to running a proper 12 volt compressor fridge. However if you have sufficient solar it can be done. Certainly on a day with as little as two hours sun and the rest of the day overcast, with this setup it will work.

Note, the inverter is a Giandel 1000 (2000 surge) watt pure sine wave unit which are only a bit over $100 these days. The 300 watt solar gear was $175 from Ebay. I added 15 meters of 6mm wire (about $40) as it is essential to be able to chase the sun to get best solar results. A big change from 2004 when I paid $750 for a 64 watt solar set up.
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Reply By: Notso - Tuesday, Oct 29, 2019 at 10:54

Tuesday, Oct 29, 2019 at 10:54
Yes, that's something I looked at doing a while back. A lot of these little bar fridges only use 60 or so watts. As long as the inverter can handle the start up draw.

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AnswerID: 628394

Follow Up By: Best Off Road - Tuesday, Oct 29, 2019 at 12:02

Tuesday, Oct 29, 2019 at 12:02
Yeah, tried it on a 600 watt modified sine wave years back at it wouldn't start. Apparently 240 fridge compressors like clean power and plenty of it.
FollowupID: 902747

Follow Up By: Notso - Tuesday, Oct 29, 2019 at 12:19

Tuesday, Oct 29, 2019 at 12:19
Yes, it's the start up current that uses the current, once it settles down it'll draw the specified watts. I never actually did it but thought it was feasible.Inverters are very efficient these days and Pure Sine Wave has come way down in price. I don't think a Modified Sine Wave would do the trick.
FollowupID: 902749

Follow Up By: Kazza055 - Tuesday, Oct 29, 2019 at 13:46

Tuesday, Oct 29, 2019 at 13:46
Plenty out there doing this now and I will go this way if my 3 way fridge dies.

Mostly that are fitting inverter fridges around the 200 - 300 litre and have them running on small 300w inverters.

Much better cooling and at a much cheaper price.
FollowupID: 902755

Reply By: SCUBADOO - Tuesday, Oct 29, 2019 at 13:50

Tuesday, Oct 29, 2019 at 13:50
About 10 years ago we fitted a 120l cheap bar fridge to our camper. A 600W PSW inverter JUST started the fridge. 1000W would be a more logical choice. A modified sine (square) wave inverter caused so much rumbling and growling from the compressor motor that it was obviously unwise to continue down that path.

Our $NZ700 255l Samsung Digital Inverter mains fridge running via a $100 300W PSW inverter has now survived 5 years of full time travel. It has never been turned off. Average current draw over that time from our 13V nominal setup has been 2.45A.
Replacing the original 175l Dometic 3-way has saved us $5000 in LPG refills and counting.

AnswerID: 628400

Reply By: Mikee5 - Tuesday, Oct 29, 2019 at 15:56

Tuesday, Oct 29, 2019 at 15:56
I am ignorant about soft start modules but will one of these reduce the start up demand from a fridge motor?
AnswerID: 628403

Follow Up By: SCUBADOO - Tuesday, Oct 29, 2019 at 16:24

Tuesday, Oct 29, 2019 at 16:24
I did try soft start circuitry both commercial and home-brew 10 years ago on the bar fridge with not a lot of success Mike.
The best that I could manage at the time made the difference between the 600W PSW inverter JUST starting the fridge and making it a little less stressful. A 500W unit never worked. It was not worth my effort. Perhaps others have had more success?
A larger inverter was a more reliable final option.
FollowupID: 902763

Follow Up By: Best Off Road - Tuesday, Oct 29, 2019 at 17:01

Tuesday, Oct 29, 2019 at 17:01
Decent PSW inverters are that cheap these days it's the easiest way to go. And it will run a two slice toaster LOL.
FollowupID: 902768

Follow Up By: Member - rocco2010 - Tuesday, Oct 29, 2019 at 17:47

Tuesday, Oct 29, 2019 at 17:47
Toaster? That's won me to the idea.
FollowupID: 902771

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