12v Electric Fridge Question

[field & stream]

Originally Posted by Boxite

Why all the talk about absorption refrigerators going the way of the dinosaurs?
They still make them and surely one can still order them, even on trailers that are standard 12v….. ?

They still make and sell them, I bought a replacement for mine recently, but there is talk of them being discontinued. The problem with replacing an electric- only fridge in a modern Airstream is that they eliminated the venting required for an absorption fridge, and it would require significant and expensive body work to accommodate one.

[Adam Geuss]

Originally Posted by AgBullet

No one in this thread has actually answered the OP's question. I read the request as wanting to hear practical experience boondocking with 2 AGMs and 300w solar. I'm very interested to know as I have a 23 GT27 on order with the same configuration.

Right on and thanks for restating the request for information. I’m equally interested.

One response was really positive stating no problems with 380 watt set up and agm batteries. I was surprised but was equally thankful getting that positive info.

My older set up, 2016 23’ International Serenity with no solar would run my two batteries down to RECHARGE required with 12 to 18 hours of fridge use. I always had a 3000watt Honda generator at the ready. I’m not keen on non gas powered options for refrigerators but maybe I’m just old? I’m equally hesitant to buy an all electric vehicle. It isn’t cost but doubt about lower overall life cycle cost for energy.

[John Ware]

I'm interested in the answer to the OP's question too. We walked a long way through the marsh and never got to the duck blind.

[field & stream]

As one who inadvertently contributed to the temporary diversion of this thread, I apologize.

Respectfully, I submit that those who are looking for “an answer” will never find “an answer”. The number of variables precludes a simple answer. However , responses #14 and #17 above do a good job of of laying out the variables and the range of expected performance.

[Last Mango]

We have no trouble doing what you are asking about with our 25 GT with the Norcold, 370 watts solar on the roof. Precooled the day before while in storage and then loaded with all precooled food. We do carry a 2500 propane/gas generator for added convince if needed. We have no concerns regarding the electric fridge fears if batteries are shunt monitored and some common sense is used. Boondocking for 3-7 days and then moving on.

[s1000pre]

The time of year can affect it as well. Currently in Tucson, clear sky: my 360 watt solar produced a Pmax of 165 watts and 1.02 kWh. Since the sun sits low in the sky and the awning side is facing south, I can pretty much right off the (2) 90 watt panels on the drivers side. If your single panel is facing south, your other 2 panels will be rendered useless. Due to shadowing.
Try to park your trailer so the front or rear are facing south. You won’t get as much shadowing from AC units etc.
I decided yesterday to not sell my 200 watt portables. They do a great job replacing 10-11 amps/hr from 10:30amish-5pmish, they replaced about 60amps yesterday. My roofs 360 watts produced about 1/2 that.

[Bcc75]

Thanks to those that responded with answers(even somewhat) to my original question. I know these threads can go down a rabbit hole quick an that's ok too. Makes for good entertainment.

For the record, I'm not a newbie at this. Just a newbie with solar and 12v fridge. I would never begin a trip with depleted batteries. I really just posed the question about pre-cooling the fridge on batteries only as just one possible scenario. One could want to know the answer to this as it pertains to days of boondocking, as many on the thread have stated. Another scenario would be situation that happened to me last year. We were in an established RV park with full hookups and the power to the park went completely out due to power pole issue down the road. It was out for 12 hours straight. I had no solar , lead acid batteries, and absorbtion fridge on propane in that situation. We did ok with that but I think we all need to be prepared for those types of things regardless and need to understand the capabilities of our equipment.

My review so far of the new fridge(still brand new to me so ask me again in a year)
1. more interior space in the fridge and freezeer than our old one.
2. Our previous was a rear bed model so the fridge had those annoying loud cooling fans. Compressor unit does not.
3. The fridge compartment on our old trailer got very hot, due to the nature of the operation. This in turn made the pantry that was right beside it very hot. In some cases , the pantry was unusable for items that were prone to melt or heat sensitive. It also skewed the room temperature sensor that was on the other wall next to the fridge but that just a poor placement by airstream.
4. less initial cool down time.
5. From what I hear, high ambient temps do not affect it as much as the absorbtion units. Here in the deep south, that's a big deal in the summer. I will report back on that this fall.

Again, time will tell.

[Rich Jenkins]

Originally Posted by Bcc75

We just got our new 2023 Globetrotter. It has a Norcold 12v Electric Fridge.
We also have the factory 300w Solar panels and AGM batteries.
Our previous Trailer did not have Solar and we had the 2 way 120v/Propane Fridge, so I'm new to these things.
Can anyone tell me how long the 12v Fridge will run on batteries (from a full charge) before the batteries have to be recharged?. Or better yet, how long can it run with just solar replenishing the batteries? Assuming good solar conditions.
Reason I ask primarily is that I want to be able to turn my fridge on prior to trip and leave the trailer sitting in my yard for a day or so and not have worry about having to plug in to 120v power.
I know the earlier versions of these 12v refrigerators were power hogs but I've heard they have gotten better.

Thanks

I'll have a go at answering your question. This is a "Spherical Cow" aka engineering estimate, and you may need to adjust for real world / your equipment.

I have a 2022 GT23FBT with a Nova Kool 6.8CF RFU6800, MPN #690770. Based on what I have been able to find out, the fridge consumes 5.2A DC when the compressor is running. If you assume that the compressor needs to run about 15 minutes out of every hour, then every day the fridge will consume 24 x 0.25 x 5.2 = 31 Ah.

So theoretically using these numbers, if your solar replaced approximately 30 Ah every day, you should be able to run the fridge indefinitely. Of course you could refine that estimate by going to the Nova Kool web site for your fridge to get the current the compressor is using, and estimating how often the compressor kicks on, for what you have normally loaded. I'd say based on what I recall, sitting in the dinette, as the fridge hums in the background, it runs kinda sorta maybe 15 minutes out of the hour, but I've never sat and timed it. 15 minutes is just a guess.

As a real world example, during Hurricane Ian, we decamped to West Palm Beach to a hotel (we lived maybe 20 miles north of landfall at the time). I had hooked up the trailer and switched on the electric, in case we needed to shelter. Sitting in the parking lot where we stayed, I noticed the fridge stopped working after a couple days. Obviously we had cloudy conditions for most of the time as the storm swept over us. I have the minimal solar package installed by Airstream (It might be 90W, and just a couple of the AGM batteries, but I'd need to check) for our little trailer. Bottom line, for my rig, for my batteries, in cloudy conditions, the fridge only ran 24-48 hours. You'll be much better off than me, with 300W of solar, but IDK what size fridge you have in your GT.

I do have experience with three previous trailers, all with Absorbtion fridges. I'd say real world that the DC fridges are much, much better at cooling down, and keep the food colder in hot climates, without the need for external fans when running on Propane. And no leveling, of course. But they are hard to beat for using the least amount of electricity. As far as I know the only thing the absorbtion fridge needs for DC is for the control board/logic and spark the propane ignitor.

Hope this helps.

[field & stream]

Helpful information from Nova Kool tech support regarding cycle time at varying ambient temperatures:

70 degrees — 35-40%
80 degrees — 55%
90 degrees — 100%

[GettinAway]

Originally Posted by dznf0g

Correct. I frankly have never seen the value of a 3 way gas absorption fridge. The 12 v mode is counter to any kind of realistic battery management. So is a compressor fridge. UNLESS, one has a very large battery bank, a large capacity dc-dc converter and a large solar system.
I rue the day when gas absorption is no longer available.

All this for my travel and lifestyle over almost 40 years of trailer traveling.

We have a 3 way fridge in our 2020GT. The only time we use the 12v option is when we are actually driving down the road. Actually I leave it on “automatic” and it switches itself. Same for when we have elec or boondocking. (It switches to propane automatically)

[dznf0g]

Originally Posted by Boxite

Why all the talk about absorption refrigerators going the way of the dinosaurs?

They still make them and surely one can still order them, even on trailers that are standard 12v….. ?

Well.....there is already noise about banning gas stoves (houses-surely rvs next) . When that happens, I'm sure water heaters, furnaces, fridges etc will be next.
Watched a video from another trailer maker. There was an off the cuff comment that induction stoves are coming and no gas is " the way of the future " . They already only do compressor fridges.

[civeng99]

Originally Posted by Rich Jenkins

I'll have a go at answering your question. This is a "Spherical Cow" aka engineering estimate, and you may need to adjust for real world / your equipment.

I have a 2022 GT23FBT with a Nova Kool 6.8CF RFU6800, MPN #690770. Based on what I have been able to find out, the fridge consumes 5.2A DC when the compressor is running. If you assume that the compressor needs to run about 15 minutes out of every hour, then every day the fridge will consume 24 x 0.25 x 5.2 = 31 Ah.

So theoretically using these numbers, if your solar replaced approximately 30 Ah every day, you should be able to run the fridge indefinitely. Of course you could refine that estimate by going to the Nova Kool web site for your fridge to get the current the compressor is using, and estimating how often the compressor kicks on, for what you have normally loaded. I'd say based on what I recall, sitting in the dinette, as the fridge hums in the background, it runs kinda sorta maybe 15 minutes out of the hour, but I've never sat and timed it. 15 minutes is just a guess.

As a real world example, during Hurricane Ian, we decamped to West Palm Beach to a hotel (we lived maybe 20 miles north of landfall at the time). I had hooked up the trailer and switched on the electric, in case we needed to shelter. Sitting in the parking lot where we stayed, I noticed the fridge stopped working after a couple days. Obviously we had cloudy conditions for most of the time as the storm swept over us. I have the minimal solar package installed by Airstream (It might be 90W, and just a couple of the AGM batteries, but I'd need to check) for our little trailer. Bottom line, for my rig, for my batteries, in cloudy conditions, the fridge only ran 24-48 hours. You'll be much better off than me, with 300W of solar, but IDK what size fridge you have in your GT.

I do have experience with three previous trailers, all with Absorbtion fridges. I'd say real world that the DC fridges are much, much better at cooling down, and keep the food colder in hot climates, without the need for external fans when running on Propane. And no leveling, of course. But they are hard to beat for using the least amount of electricity. As far as I know the only thing the absorbtion fridge needs for DC is for the control board/logic and spark the propane ignitor.

Hope this helps.

Is all about what you want and how you camp. I would never ever ever want a 12v only fridge. We all decide.

That said I have no desire for all of the unnecessary complexity in the new units either. I don’t want apps to control my rig. Exactly why I camp. To be with the dogs in the woods avoiding using tech.

[Bill M.]

Fridge and freezer will probably be running max for the first day to cool it and the contents down. I think 1 day for AGM's. I have no solar and no idea how much power it adds. I am pretty sure if I had a 12 volt DC fridge I would add Lithium batteries. I like the idea of using an extension cord for the cool down. Not much draw from the fridge so a long run is okay.

[trsvax]

I don't have exactly that setup but I do have solar/lithium and both a compressor and propane fridge (long story).

I would say if you are not parked under trees the answer is most likely yes but there will be times when you can't. If you really want to have a pretty good idea when you are actually trying to do it you'll need a shunt and a weather forecast so you can tell in real time what the battery status is and which direction it's likely to go.

There are just too many variables to give a yes/no answer.

[Rich Jenkins]

Ok, using 50% for fridge duty cycle as a better estimate, based on the numbers posted by @field & stream in post #29, I now get:

24 hours x 0.5 x 5.2 Amps = 62 Ah will be consumed by my fridge every day at 80F.

I looked at my rig yesterday, and I have two Diehard 24M-AGM batteries. The literature I can find for those indicates they are 70 Ah ea, so I have a combined 140 Ah. It makes sense now that my fridge only lasted a day or two in cloudy conditions during our Hurricane evacuation.

[Bill M.]

Two 70 amp hour batteries only will provide 70 amps power without hurting the batteries.

[jftompkins]

We use about 30Ah/day just the basics with absorption refrigerator and replenish 110Ah useable storage AGM batteries; with 120W portable solar which can give us up to 40Ah/day good sun. With a compressor, a refrigerator as others have said with estimate an additional 50-60Ah/day - another 200W of solar for makeup. Did a spreadsheet estimate going to check with a DC ammeter at batteries later this year by turning e- demands on/off to verify.

[thumper1946]

Originally Posted by AgBullet

No one in this thread has actually answered the OP's question. I read the request as wanting to hear practical experience boondocking with 2 AGMs and 300w solar. I'm very interested to know as I have a 23 GT27 on order with the same configuration.

I have a vitrifigo frig In our 28 ft airstream for several years now 500 wath solar panels on top .lifuam battery's .boon dock for 16 day in Idaho never had to turn on the generator we do a lot pf boon-docking love th efrig 12 volt

[jftompkins]

Originally Posted by jftompkins

We use about 30Ah/day just the basics with absorption refrigerator and replenish 110Ah useable storage AGM batteries; with 120W portable solar which can give us up to 40Ah/day good sun. With a compressor, a refrigerator as others have said with estimate an additional 50-60Ah/day - another 200W of solar for makeup. Did a spreadsheet estimate going to check with a DC ammeter at batteries later this year by turning e- demands on/off to verify. Attachment 427937

With 300W up top and a compressor refrigerator ….just go for it see what happens based on your overall e- demand based on all the variables. Possible option would be to add a portable solar to supplement IF not enough to keep batteries charged….from the experience.

[uncle_bob]

Hi

Typically we run about 50AH a day doing absolutely nothing in our trailer and running a propane fired fridge.

Bob