Fridge / Cooler Fridge Cycle Times/watts Used Per 24 Hours?

I've read through the older fridge threads but was wondering if anybody has any recent experience with actual cycle times and/or watts used per 24 hours on a Dometic or possibly Iceco fridge. From the prior threads I think I would probably carry the fridge in the TV while getting somewhere, but when the destination is bear country (pretty much anywhere in California) the fridge would have to go back in the camper and charge from the house battery while camped/parked. (Otherwise I would probably prefer to get a larger one.)

I've watched many youtubes and the reality is, there are a lot of factors influencing how often the compressor will kick on and off. I will have rooftop solar to power the battery when not on shore power. I do think/hope that will probably make it a mostly a non issue, but I've learned never to assume anything. I am curious how people may be dealing with it these days as the technology creeps forward.

Thanks for your thoughts.

 

Hi John C.

To answer you question, no we don't have tangible experience with W/day on the Dometic. Most of our trips are 3 nights or less and for that we prefer the analog cooler. We value having the Dometic at home during COVID for holding overflow from larger shopping trips (less frequent trips to store). So, unexpectedly, we have put a lot "miles" on our Dometic without leaving the house. I'm sure W/day will vary widely based on ambient temperature, but I am curious to see others' replies to your post.

Cheers,
--Ken

 

I'd be more concerned about keeping it in the car, simply becuase first car batteries are not deep cycle and don't deep discharge well. Second, if you do get too low it could be a bit unpleasant getting things up and running again.

I can tell you, that the deep cycle battery on board the CI would keep it running for a couple days (Friday late to Sunday Morning) without problem, even without solar. Our experiment wasn't intentional, our onboard charger croaked. We noticed that the lights were a bit dim on Sunday... We were using a CF35

The power consumption varies greatly based on what you have in the fridge and the ambient temperatures ...

 

I agree with this. We've been using the cf35 for 7 years now and have found that our agm battery will handle the fridge for a couple of days but it's *very* dependent on ambient conditions.

I posted the dometic chart a few years ago but darned if I can find it so have attached it again. Note that at 89 degrees ambient the running time is 40% more than at 68 ambient.

I've never seen the fridge draw 6 amps, though. 4 to 5 is typical.

We always carry the fridge in the TV while going down the road, then move it to the trailer while camped. If it's not raining and there's not much threat from critters, I prop the galley hatch open a bit using a hunk of 2x4 on its side. That fridge puts out some heat so ventilation is good. We'll also just leave it on the side table sometimes. The fridge does have the insulating cover.

 

It would only be in the car while driving between Point A and Point B.

 

Your usage mirrors what my intent would be. But there are places, especially in CA, where it has to stay in the "closed" trailer or in a bear box. Leaving the galley hatch open when not in use can get you in trouble with the authorities. Yosemite is quite strict about that.

I think your spec sheet is an older one. The current models, (CFF 35 & CFX3 35) both show high battery cut out at 11.8v.

For sure, ambient temps play a big part in how much power you use and how often it cycles. I noticed too the published specs are based on a fridge setting of 41 degrees. I don't think that would be acceptable to me. I'd prefer something in the 34-35 range. So, that too will cause an increased draw. The house battery only holds 70 Ah.

 

we generally keep ours set at 38 which yields a temp lower than that according to the dometic temp display. It turns on at 38 but seems to lower the temp to 35 or 36. And of course the lower part of the fridge is colder but at 38 the stick of butter in the upper storage stays nice and hard.

I keep the battery set on the low cut out setting. I found out the hard way that the surge when the dometic turns out very briefly lowers the voltage enough to shut down the fridge at the higher settings. It works great at that lo setting and has been very reliable for years.

yep, you've got to keep the galley closed sometimes. If it isn't too hot that's not a problem. If it is then the battery life is distinctly shorter. We camped in Death Valley one October (Mesquite Springs, I think). It was hot. I was curious to see if our 85 watt panel in lots of sun could keep up with the high demand of the dometic in a closed galley, and it did. And sometimes I've found that just a couple of hours of good sun can make a real difference in eastern campgrounds.

I wanted to quit worrying about it, though, so I installed a CTEK charger. It turns the car into a nice, quiet generator that gives the AGM battery exactly what it wants. Don't have to use it very often but it's sure nice when we need it.

 

Wouldn't the low setting (or even medium) be too low to be of any use? By the time it kicks in, the battery would be dead.

I do think even a minimal amount of solar would probably be enough to keep the battery going. But I guess that's the ultimate question.

I'm hoping to get to Death Valley this winter. Possibly December or January.

 

One thing to consider, is the fridge does have a low voltage cutout. In my car, I’d keep it at “high” which is a 12 volt cutout. Battery damage aside, I just don’t want to get stranded with a car that won’t start. 12 volt is right at that point where everything better work the first time.

6 amps at 20% duty cycle. Say 50 amp hours in a car battery……so 25 useable….

13 hours would use 1/2 of a car battery….assuming all healthy? I’ll have to do some spreadsheet math tomorrow. I’m too tired at the moment and need my sliderule . But I think I’m close….

EDIT: I verified the formula, and it goes something like this:

BatteryLife=BatteryCycle in Ah / Load Current in Ah.

On a 100% charged, and 100% healthy battery, and a 50 Amp Hour rated battery. Your battery is likely smaller unless you're driving a full size truck. But the math is easier ...Assume you don't want to discharge below 50% state of charge. so Figure 25 Amp Hours available. Car batteries are not rated in AH, they are rated in CCA - thats a topic for some one who knows more about car batteries than me. But 40-50ah is what was given by others asking.

25ah (1/2 of 50amp) / 6amp load current (at 100% run time) or ~4 hours 10 minutes

The CF35 will run somewhere around a 25% Duty cycle -- above estimates assume 100%. So multiply those numbers by 4. This too is an assumption, probably lower but possibly higher. This depends on air temperature and set temperature. The book says 15-17%, but those are ideal conditions.

Multiply to say 20 hours would be the maximum run time to deplete 50% of your battery.

This assumes a lot. Mostly battery overall health, and combined "other" draws from the car itself (clocks, on-board computers, Alarm systems etc) - if you leave a light on in the car, or have a lot of electronis plugged in, the the battery will discharge faster. This formula is just for the fridge itself, assuming nothing else is present.

This "feels" right to me based on what my CF35 performance was like when camping with it. I would make darned sure I cary a jump pack or jumper cables with me and make sure that jump pack is pre-charged as well - nothing worse than a dead battery, except 2 dead batteries.

 

I only use the low setting because when the battery voltage was down a bit, the surge when the dometic came on would cause the voltage momentarily to drop enough to go below the medium or high cut off setting and shut down the fridge. Because of that surge, though, the battery wouldn't ever get to completely dead due to the dometic. It just wouldn't start up if the battery were maybe below 50%.

I'm just guessing though because I'd never let it get anywhere near that low. I determined that if we were going to dry camp with a dometic then we had to have good info about our battery's state of charge. So I installed a trimetric monitor. When it says the battery is anywhere near, say, 70%, I charge it back up. Maybe not all the way but enough, maybe 90%.
The trimetric gives me more info than I need but it also has a reminder when to charge the battery fully as well as an indicator that says when the battery has met all the criteria to be truly fully charged.

The trimetric and the CTEK charger make dry camping with the dometic essentially non-stressful, even in the shady east. I recommend both of them.

And I don't *ever* run the dometic off the car battery when the car's not running. Car batteries aren't designed for that sort of usage. That sounds like a recipe for disaster to me. I'd suggest only putting the fridge in the car while traveling. Much cooler ambient temp and no load on the trailer battery.

 

I carry an extra 50 Ah battery when we take the Dometic. It is in a closed box with a coulometer and volt meter, and I set it up to charge from the tow vehicle with a battery isolator when we are driving (also strapped down). I have put the fridge and the battery in a bear box and it keeps running for a couple of days even when it is pretty warm. When in camp, the fridge and battery usually stay in the tow, but won't deplete the car starting battery. I now also have the ability to charge the auxiliary battery with a solar panel but I haven't had a chance to try it out yet; if it is sunny the fridge should be good for a long time without effecting the car battery or the trailer battery.

 

I plan to purchase a solar generator/power station at some time in the future. Trying to determine my needs/desires and feature trade offs vs cost is a juggling act. It would certainly solve the bear box issue though.

 

A jackary 500 would do nicely for this, even if you did more than just run the fridge….and they seem reasonably well liked by reviews….

 

I prefer something with a larger inverter (at least 1kw) and maybe more Wh storage. They aren't cheap and if I'm going to bite the bullet I would probably rather bump up in size. There are a few different brands I'd consider in addition to the Jackerys.

 

My needs are minimal…basically a couple USB level powered devices, fridge and a laptop. 500 would get the job done. Any more would be adding AIr conditioner….which immediately makes “solar generators” pretty useless. Which is why 8 have a suitcase generator…

I keep hoping the tent camp sites will start getting 1 15 amp circuit . I will NOT miss pulling a 25 foot 50 amp power cord around….man, those things are a PITA.

 

I keep my fridge in the bed of the truck connected to a Jackery 1000 which charges while I’m driving via a Victron Energy Orion-Tr Smart 12/12-Volt 30 amp 360-Watt DC-DC Charger, Isolated . Since I have a hard cover over the bed of the truck I don’t have to remove it and put it in a bear box. When in camp I keep the Jackery charged with a 100 watt Jackery solar panel. Like the Jackery panel as it folds up small and is very light.

 

I have a SnoMaster fridge…too big to fit in the rear of the trailer so it’s always in my 4Runner. Haven’t had any issues in bear country…yet! Friends that have had both prefer the efficiency of the SnoMaster to the Dometic. For a few years I ran it off my car battery, but have since shifted to a GoalZero 400 Lithium with a 100w solar panel since we’re often in very remote locations. My older CI has the smaller battery, so don’t think it would be a good answer anyway.

 

This past weekend I was only getting about 4-5 hours of use out of our Dometic C-35 before I had to start up the generator and recharge the camper battery. Dometic was set at low cutout. It was hot and wet due to Hurricane Henri. My electric issues continue.

 

That seems really short --- two immediate thoughts:

1] What is the condition of the battery itself --- if it is weak, this would explain the short run-time. Auto parts stores typically can test these for you at no cost to you -- at least around me. They just want to have the opporutnity to sell you the replacement. If they want to charge a fee, check the one next door...

2] What was the condition of the fridge itself? It needs to have a good amount of area around the vents (10-12 inches as I remember) to allow the hot air to escape. Was the fridge sitting in the sun? Shade is best, further insulated by an insulated cover is better.