Ran an inverter test comparing two small fridges to replace the old 3-way in the 1981 TC. There have been several threads on using 120v fridges on inverter, so this adds something to the data base.( The 3.2 is the size we want to fill the hole where the old fridge was and the 1.7 is way too small, but had them both before returning the 1.7 so tested it while in hand :) )Both fridges were tested at 1/2 cold setting on dial.A. Danby 1.7 cuft model DCR017A2WDB-- back label says 115v/1.3a (AC)Tested on 2000w Vector MSW inverter (as mounted in the TC)--it ran the fridge ok.Switched to 1000w Xantrex PSW inverter in 5er where the Trimetric can show the draw. Fridge ran ok. Start-up draw jump to 20a (DC) then quickly fell off to 8.5a then after a minute settled at 7.6a. After three minutes it shut off --assume fridge at set temp, didn't check that.No test of cycling times to maintain temp was done.B. Igloo 3.2 cuft model FR320--back label says 115v/0.8a (AC)Tested on 2000w Vector MSW inverter in TC--it ran the fridge ok.On 1000w PSW inverter in 5er, ran ok.Start-up draw jump to 30a (DC) then immediately dropped to 4.0a then back up to 4.3/4.4a and held there for ten minutes and shut "off", holding at 0.2a -- didn't check its temperature.No test of cycling times done.Interesting how the Igloo is almost twice the size but draws much fewer DC amps. The daily AH draw is another thing of course where they might cycle differently. The two fridges are in this link if anybody is curious:http://www.londondrugs.com/Refrigerators/appliances-kitchen-refrigerators,default,sc.html

interesting Data. Now go get the smaller one back and do some more testing to satisfy my curiosity.Seriously though, that 0.2 amps after the compressor turns off is interesting. What is the standby current on your inverter? Did you factor this out?I wish my clampon DC ammeter recorded inrush current, but my Vitrifrigo 1.8 cubic foot fridge with the compressor on the slowest setting of 2000 rpm, starts off at about 2.8 amps and tapers to about 2.2 amps 5 minutes later when the compressor shuts off. It runs less than 20 minutes an hour upto about 80F ambient to hold 33.5f Interior temps.I like my cheap beer, cold.

The standing draw before turning on the fridges was 0.9a showing on the Trimetric from the various parasites and the inverter itself. I subtracted that 0.9 from the readings with fridge on.The starting surge I saw may not have been all of it. Not sure of the reaction time for the Trimetric to show that. ISTR it tries to average. Anyway, there is a surge. There was info in another thread that the surge is maybe twice what I saw, as shown by a was it 600w inverter ??? conked out, but his 1000w held ok for the start-up on a small fridge. So don't assume the 30a shown in the OP means you could run this 3.2 fridge with a 400w inverter!

Getting the surge numbers for the little air conditioner has been hard. The clamp on shows it jumping well over 40 amps but it drops down so fast. I'll have to see if the kill a watt can catch anything.

The TC is supposed to last three or four days off-grid then be home to recover the two T-1275s from however low they got. Not too worried about going below 50% on those things.However, now we have a 120v fridge with no LP option. Even at 4.5 amps cycling however much, it looks like we will need a recharge somehow before getting home. Or the TC will have to get some solar! Maybe I can use my portable 230w that goes with the 5er, on the TC roof in a tray instead of getting a second solar set. Now I wish I had not sold my 130w panel last summer. It would have been perfect for this job. I need a better crystal ball. :(

Get something small and inexpensive, enough to cover the fridge so that you can continue the plan you have.

Small Fridge on Inverter for TC-1.7 vs 3.2 cuft Report

landyacht318
Explorer
Apr 03, 2015
interesting Data. Now go get the smaller one back and do some more testing to satisfy my curiosity.

Seriously though, that 0.2 amps after the compressor turns off is interesting. What is the standby current on your inverter? Did you factor this out?

I wish my clampon DC ammeter recorded inrush current, but my Vitrifrigo 1.8 cubic foot fridge with the compressor on the slowest setting of 2000 rpm, starts off at about 2.8 amps and tapers to about 2.2 amps 5 minutes later when the compressor shuts off. It runs less than 20 minutes an hour upto about 80F ambient to hold 33.5f Interior temps.

I like my cheap beer, cold.
BFL13
Explorer II
Apr 03, 2015
The standing draw before turning on the fridges was 0.9a showing on the Trimetric from the various parasites and the inverter itself. I subtracted that 0.9 from the readings with fridge on.

The starting surge I saw may not have been all of it. Not sure of the reaction time for the Trimetric to show that. ISTR it tries to average. Anyway, there is a surge. There was info in another thread that the surge is maybe twice what I saw, as shown by a was it 600w inverter ??? conked out, but his 1000w held ok for the start-up on a small fridge.

So don't assume the 30a shown in the OP means you could run this 3.2 fridge with a 400w inverter!
JiminDenver
Explorer II
Apr 03, 2015
Getting the surge numbers for the little air conditioner has been hard. The clamp on shows it jumping well over 40 amps but it drops down so fast. I'll have to see if the kill a watt can catch anything.
BFL13
Explorer II
Apr 03, 2015
The TC is supposed to last three or four days off-grid then be home to recover the two T-1275s from however low they got. Not too worried about going below 50% on those things.

However, now we have a 120v fridge with no LP option. Even at 4.5 amps cycling however much, it looks like we will need a recharge somehow before getting home. Or the TC will have to get some solar!

Maybe I can use my portable 230w that goes with the 5er, on the TC roof in a tray instead of getting a second solar set. Now I wish I had not sold my 130w panel last summer. It would have been perfect for this job. I need a better crystal ball. :(
JiminDenver
Explorer II
Apr 04, 2015
Get something small and inexpensive, enough to cover the fridge so that you can continue the plan you have.
BFL13
Explorer II
Apr 04, 2015
The cheapest around here now is a guy that sells mono 100s for $125 that do about 5.6 Isc. One of those might do it in the summer but with no solar you can count on in the winter, it won't do.

The whole point of the TC (besides being a fun project) is for going to 3-4 day dog events off-grid on the Mainland. Short truck length (with TC sticking out the back) is cheap on the ferry compared with the long 5er plus truck combo)

I might be looking again at my "emergency" charging via truck battery while idling the truck trick like in that other thread every couple of days. Option there is via a second inverter to run a 35a Vector or just use a set of jumper cables for ease of setting that all up.

It is not at all convenient to use the installed 2000w inverter from the truck battery to run the converter to charge the house batteries.

Drat, this is getting complicated! :)
BFL13
Explorer II
Apr 05, 2015
Started an AH test run on the 3.2 to get an idea of daily draw. (fridge plugged into 5er where the Trimetric is.)

With dial at 4 of 7, ice cube tray full of water and another tray of water in the lower fridge part, got the first 6 hour results:

Ice cubes in the freezer and also the water down below froze, so dialed it back to 3 of 7 for the next while.

11.6 AH in 6 hours, so 1.93 amps. 1.93/4.4 = 44% of the time cycling on. We'll see how it goes tomorrow for the full 24hr run results.

at 10 hrs, 16AH with the dial reduced to 3 the last four hrs, so averaging 1.6 amps and 1.6/4.4 = 36% Fridge still too cold so trying dial at 2.5 overnight.

48AH a day just for the fridge with a 270AH bank isn't going to work for a long weekend without some incoming AH. I am building a tray for my 230w panel to go on the roof of the TC when off-grid. Good thing the panel is portable and not nailed to the 5er's roof.
JiminDenver
Explorer II
Apr 05, 2015
So you will go from running your batteries down for days to who cares, you have the power. :)
BFL13
Explorer II
Apr 05, 2015
To finish up the AH report, the 24 hr run came out at 29.4AH or 1.23a which is 28% time on when it is at 4.4a.

However the camper was not heated and ambient was below 50F daytime and down near freezing last night.

I expect the results this test are a bit low for daily AH in real life, but the test did its job of proving the need for additional battery charging even at the 29AH rate.

It also gives an idea of how much solar would be needed to compensate for the fridge, assuming you know what sort of AH haul particular solar sets can do where and when you will be camping.

Anyhow that's that solved.
westend
Explorer
Apr 06, 2015
Thanks for the report, BFL. It should give some an idea about AH draw for these small 120V refrigerators. FWIW, I guesstimated the startup draw of my 1.8 cu. ft. fridge to be about 6 amps at 120V.

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