Residential fridge run time on battery

[Livin' the Dream]

How much time can a residential fridge run on batteries? We're looking at doing a lot of boon-docking and trying to decide whether or not, if a propane/electric standard RV fridge would be a better choice. We will have generator capability and would use that sparingly to charge batteries or to run high use items. How many batteries do you recommend having?

[bertschb]

If you plan to do a lot of boon docking, you will either need to run a generator a lot or have a decent solar system and battery bank. The longest I ever ran the residential fridge on batteries in our last rig was about 8 hours while driving. That was with the two batteries the dealer installed. I have no idea how long I could have gone before depleting the batteries but I suspect I was getting close at 8 hours. But, there are a ton of variables. Our fridge was cold when I started and full of cold food. Plus it was cold inside and outside the RV so the fridge didn't need to run much.

We love residential refrigerators and would rather install a big solar system and bring a generator if boon docking than give it up for a propane fridge but we are definitely in the minority in this respect. I think just about everybody else would recommend a propane fridge if you plan to boon dock a lot.

[TucsonJim]

How much time can a residential fridge run on batteries? We're looking at doing a lot of boon-docking and trying to decide whether or not, if a propane/electric standard RV fridge would be a better choice. We will have generator capability and would use that sparingly to charge batteries or to run high use items. How many batteries do you recommend having?

Hi there. If you can provide the model number of your refrigerator, I should be able to get you an answer on power consumption.
If you ever want to know exactly how much power you're drawing, I'd recommend purchasing a battery monitor. There are lots of brands available, but I'm partial to the Victron BMV-712. It runs about $220 on Amazon. It allows you to monitor exactly how many amp hours you're drawing from your battery bank. And the 712 can be blue-tooth connected to your phone so you don't have to do extensive wiring to get a read out.

What type of batteries do you have now, and how are you monitoring the state of charge? How many of those batteries are installed?

Jim

[Livin' the Dream]

We currently don't own an RV, but did purchase the truck and we're looking at purchasing the 390RK early this spring. We're just trying to do our due diligence and researching lots of things. We do plan on RVing full time and have looked seriously at solar, portable generators, etc. Leaning towards 4 Lithium Ion batteries.

[howson]

How much time can a residential fridge run on batteries? We're looking at doing a lot of boon-docking and trying to decide whether or not, if a propane/electric standard RV fridge would be a better choice. We will have generator capability and would use that sparingly to charge batteries or to run high use items. How many batteries do you recommend having?

Check out TucsonJim 's thread about measuring refrigerator temperature performance. Post #25 may be particularly interesting: https://gdrvowners.com/forum/operati...=9327#post9327

The only advantage of an absorption refrigerator is the ability to run on propane. The power consumption on electricity is much, much higher than what a compressor-driven ("residential") refrigerator will consume.

There's also the performance of the refrigerator itself. Hands-down the compressor models keep the food colder and recover/cool down faster.

Again, the one advantage of the absorption refrigerator is the ability to switch to propane. Since this is done automatically by the unit if shore power is lost, it is a convenient feature.

[Second Chance]

We've been over four years full-time with an absorption (RV) frig. Our new RV is being built with a residential (compressor) frig and the solar option. I will install one or two Battle Born LiFePO4 (Lithium ion) batteries due to their constant voltage and low-draw capabilities. The setup will be more than adequate to run the frig when we're not plugged in to shore power. I'm looking forward to frozen food freezing and the frig being at the proper temp - not to mention lower electric bills when we're staying at a monthly site that meters electricity.

Rob

[Cate&Rob]

The power consumption on electricity is much, much higher than what a compressor-driven ("residential") refrigerator will consume.

I would not agree with this. Assuming that we are comparing a 120VAC (residential) fridge and an RV absorption fridge. There is a different technology 12VDV compressor fridge that may be a "game changer" for this.

My comparison is similar size (about 8 cu ft) refrigerators. The 120VAC is in our boat and runs through an inverter from a 12V battery bank. This residential compressor fridge will draw about 30A at 12VDC. The RV absorption fridge in our RV has a 300 watt electric heater. 300 watts would be 2.5A at 120V or (theoretically) 25A at 12VDC. With inverter loss, both these fridges would draw about 30A from the batteries.

A big difference in performance between residential and RV fridges is the insulation of the fridge. Our boat residential fridge runs a much lower duty cycle than our RV absorption fridge (on either electric or propane) because the residential fridge has better insulation.

Battery capacity is measured in Ah (amps x hours). A fridge drawing 30 amps on a 50% duty cycle will use 120 Ah in an 8 hour period. (30 x .5 x 8). A Group 27 lead/acid battery (standard spec for an RV) has about a 120 Ah rating . . . but (and this is important) you can only use half of this or you will risk damaging the battery if you discharge it to below 50%. So, you will need two of these batteries just to power the fridge through the night. You also need battery power for lights, maybe the furnace blower, etc.

The bottom line is that without a lithium battery bank (much deeper discharge capability) and an extensive solar charging system . . . there is a reason that RV fridges run on propane.

Rob

[howson]

My comparison is similar size (about 8 cu ft) refrigerators. The 120VAC is in our boat and runs through an inverter from a 12V battery bank. This residential compressor fridge will draw about 30A at 12VDC. The RV absorption fridge in our RV has a 300 watt electric heater. 300 watts would be 2.5A at 120V or (theoretically) 25A at 12VDC. With inverter loss, both these fridges would draw about 30A from the batteries.

A big difference in performance between residential and RV fridges is the insulation of the fridge. Our boat residential fridge runs a much lower duty cycle than our RV absorption fridge (on either electric or propane) because the residential fridge has better insulation.

The video below shows evidence that doesn't agree with your conclusion, Rob. I am not disputing your numbers from your boat's refrigerator, what I'm suggesting is that manufacturer's have improved the efficiency of new refrigerators.

The guy's residential in the video below is pulling 7 amps (12vDC) and his Dometic the expected 29-30 amps (12vDC). Both numbers are pulled right from his BMV screen (the one we're accustomed to viewing). Note that both refrigerators are not cooled down so they are running at maximum. Duty cycle is not a factor.

Your post reminded me that I was going to run a test of the small AC refrigerator I have to compare to the test I did with my Dometic. While not exactly 1:1 (due to refrigerator size difference) the results should be interesting.

[ncitro]

We currently don't own an RV, but did purchase the truck and we're looking at purchasing the 390RK early this spring. We're just trying to do our due diligence and researching lots of things. We do plan on RVing full time and have looked seriously at solar, portable generators, etc. Leaning towards 4 Lithium Ion batteries.

I replaced my Dometic fridge with a Samsung residential unit. I run four Lithium batteries, and have 1,200 watts of solar. With everything off except the fridge I can run it for two days before exhausting the batteries if I am not in sun. Obviously if in sun they keep up with no problem.

[Cate&Rob]

The guy's residential in the video below is pulling 7 amps (12vDC) and his Dometic the expected 29-30 amps (12vDC). Both numbers are pulled right from his BMV screen (the one we're accustomed to viewing). Note that both refrigerators are not cooled down so they are running at maximum. Duty cycle is not a factor.

Hi Howard,

This is quite amazing. Producing the same (or better) cooling with less than 1/3 of the power? 7x13.6=95 watts vs 300 watts for an RV absorption. I wonder if the residential fridge in the video is using the Danfoss compressor technology that Jim is investigating for the 12VDC fridge. I will admit that my thermodynamic "spidy sense" has me questioning this. If this is true, this will be a game changer for all forms of refrigeration . . . including air conditioning. If your 15,000 BTU AC could operate on 4 amps instead of 12 amps this would get AC into the range of 12V battery power. I will admit that this sounds "too good to be true" to me.

Rob

[howson]

This thread is running almost parallel to @TucsonJim's thread about measuring refrigerator temperature. The initial test I ran on the Dometic is in that thread, so to see the test on the residential (and the power consumption) see Jim's thread. To go directly to my residential frig test go here: https://gdrvowners.com/forum/operati...=9995#post9995

[Guest]

The video below shows evidence that doesn't agree with your conclusion, Rob. I am not disputing your numbers from your boat's refrigerator, what I'm suggesting is that manufacturer's have improved the efficiency of new refrigerators.

The guy's residential in the video below is pulling 7 amps (12vDC) and his Dometic the expected 29-30 amps (12vDC). Both numbers are pulled right from his BMV screen (the one we're accustomed to viewing). Note that both refrigerators are not cooled down so they are running at maximum. Duty cycle is not a factor.

Your post reminded me that I was going to run a test of the small AC refrigerator I have to compare to the test I did with my Dometic. While not exactly 1:1 (due to refrigerator size difference) the results should be interesting.

Howard,

Would this small apartment fridge use isobutane for the refrigerant? Curious, since this a new trend in the smaller units and would be about 6% more efficient than a typical unit that uses Freon for the refrigerant. Isobutane is flammable but the amount used is typically very small.

Jim

[howson]

Would this small apartment fridge use isobutane for the refrigerant?

I don't know. TucsonJim might...

[gbkims]

Howard,

Would this small apartment fridge use isobutane for the refrigerant? Curious, since this a new trend in the smaller units and would be about 6% more efficient than a typical unit that uses Freon for the refrigerant. Isobutane is flammable but the amount used is typically very small.

Jim

That's an interesting question on the refrigerant.
Both the Frigidaire 9.9 FFET11022QW which might be in the video as well as the Frigidaire 10.1 FFET1022UW show R600a (isobutane) in their wiring diagrams.

Also have seen Frigs with BLDC Inverter Compressors mentioned.
Saw a NXP Semiconductors App Note on them.

[Joesmainship]

I looked inside my Samsung Residential fridge, and the plaque inside the door says, max current draw is 1.3 amps at 120VAC. If you convert that to DC, it would be 11-13 amps, depending on what the inverter is using. But you have to also consider that the residential fridge doesn't run all the time. It cycles off and on depending on a number of factors. With 2 batteries, I think it should run for 24-36 hrs, at least. If you intend some serious boondocking, you would definitely require a generator to run several hours daily. You must also consider how much better Blue Bell ice cream freezes in a residential fridge and what would boondocking be without Blue Bell.