Experiences with running fridge off main car battery overnight for a few nights in a row?

[DaveM]

Heading out to Sedona in about a week to visit wife's family. Taking a couple days to get there and making a few scenic stops along the way. Driving our new (to me) 2016 Subaru Outback, which has a lot less space inside for storage than the old Tacoma with shell. Bringing my 36 quart Doemtic which I'd usually run off the vehicle in route and then off a portable deep cycle battery overnight at hotels or in camp. Trying to see if I can avoid the bringing the extra battery on this trip and just leave the fridge plugged in overnight to the car. Any practical experiences with this?

I've actually done this a number of times, but not for three consecutive nights and not with summer desert temps. I normally drive with fridge at 36* - 38* then at the hotel if running off the car batt I up it to 40* or maybe 42*. Batt cut off on fridge is also set to med which helps protect the batt (I could do high I guess).

 

[Superduty]

What size battery is in the Subaru?

Will you be driving the Subaru during the days, ie the vehicle battery will be recharged?

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[dreadlocks]

might carry a jumper box/cables, I tried this at first but never drove enough every day to recharge the battery fully.. eventually it was a loosing game, if you discharge it to 50% SOC it takes like 6-8h of driving to get it back to 100%.. It'd take me about 48h w/no engine running to hit 50% on a 100AH deep cycle, so if its just 8-12h overnight and you drive it 3-4h every day, it might scrape by.

We'd need to know how much power your fridge uses overnight in summer climate, and how much capacity your starter battery has in AH at a 20A rate.

 

[john61ct]

Too many critical values are unknown here.

My guess is no, you'll end up needing a jump.

If that's NBD for you, give it a shot and let us know how it went

 

[DaveM]

Driving en route probably 7-8 hours day 1, 5-6 hours day 2. I guess I only need to do this 2 nights. Battery in car is new, but not sure what size, almost certainly OEM from dealer which would be group 25. I do have a lithium jump pack. My own experiences doing this have been positive so far, but I was using a larger Interstate battery on my Tacoma. I'm ok with using the high power cut off on the fridge, nothing will spoil overnight and I can get back to cold in minutes running while driving.

Specs on Dometic 35 quart energy consumption per their website: Energy Consumption 12VDC (Ambient@90F, Internal@41F) 0.77 Ah/h

 

[DaveM]

I guess I should say, I think this will be ok, but looking for some positive affirmation from anyone else who's done same and actually took notes or something

 

[DaveM]

ah crap! Just occurred to me, the rear 12v accessory plug is almost certainly not "always-on" as mine was in the Taco. Nevermind, will toss the huge deep cycle in the back I guess. Need to start looking at a smaller set up like a Yeti400 with solar. Giving up my truck bed and shell is going to be harder than I thought.

 

[plh]

Driving en route probably 7-8 hours day 1, 5-6 hours day 2. I guess I only need to do this 2 nights. Battery in car is new, but not sure what size, almost certainly OEM from dealer which would be group 25. I do have a lithium jump pack. My own experiences doing this have been positive so far, but I was using a larger Interstate battery on my Tacoma. I'm ok with using the high power cut off on the fridge, nothing will spoil overnight and I can get back to cold in minutes running while driving.

Specs on Dometic 35 quart energy consumption per their website: Energy Consumption 12VDC (Ambient@90F, Internal@41F) 0.77 Ah/h

Group 25 is somewhere around 100 minutes at 20 +/- depending on brand etc... That should get you around 21 hours to 50%

 

[dreadlocks]

ah crap! Just occurred to me, the rear 12v accessory plug is almost certainly not "always-on" as mine was in the Taco. Nevermind, will toss the huge deep cycle in the back I guess. Need to start looking at a smaller set up like a Yeti400 with solar. Giving up my truck bed and shell is going to be harder than I thought.

Go get your self a lil trailer and build up from there, I used to do trips like your planning out of a lil diesel golf all the time.. absolutely nothing was in the hatchback but people and a few bottles of water, everyone could stretch out and get comfortable for the long hops, trailer was packed to the gills with camping gear.. had storage capacity of a short truck bed (1500+lbs of gear) but I got 36mpg @ 80mph all day long and did ~25k miles touring in it every year..

 

[Ducky's Dad]

Haul the fridge into the hotel at night and run on AC?

 

[WOODY2]

Depending on outside temps sometimes I turn mine off overnight and the internal temp may rise to 40 degrees which is still safe for food. The .77 consumption sounds very, very low. Just get a jump pack for insurance.

 

[john61ct]

Consumption is lowest keeping it running 24x7

Turning it off for a while if you're driving soon might make sense I guess, but better to just rig a setup that works no matter what.

Most efficient portable 12V compressor fridges run at around 4A when the compressor is running. That super low number is prolly just the electronics.

Average Ah per hour depends on the % duty cycle, compressor runs say 80%+ when warm food goes in, or when run as a freezer.

Only 30% as a fridge once contents chilled and cool ambients.

 

[ducktapeguy]

I've done it and you can make it work. You may have to give up some fridge space for frozen water bottles to make last all 4 days.

I usually pre-freeze a layer of water bottles to about 0F a few days before the trip (must be solidly frozen). Then set the temp setting at it's lowest setting. This will cause the fridge to run at full power whenever the car is on. At night I up the temp to about 32-37(dependent on various factors), and as long as there's frozen water in the fridge it will either never hit that temp, or cycle very rarely and the frozen water has enough mass to keep the fridge cool over night. When you're driving the during the day fridge is always on refreezing the bottles again.

Over time it's a loosing game, eventually the bottles will melt and it will take a take a tremendous amount of energy to refreeze them. But I was able to do 4 days in death valley with a weak battery and keep all my water frozen. If you're driving 5-6 hours a day it's no problem and you can probably make it a couple weeks without issue

You can easily jumper the relay in a subaru to keep the rear outlet constant on. The one thing to watch out for is whether the outlet can handle long periods of continuous current, especially through a lighter plug. Some of them heat up a lot after a few hours of constant power draw

 

[reaper229]

If you get some hot temps outside it will take more amps...direct on the starting battery sounds like a bad idea,you better buy a small battery and when you take the road just put it in your 12v car socket but after that just hook it up on a second battery.

I use a DIY solar generator with my Costway fridge.

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[DaveM]

Nice set up. You got a write up on that battery box? I have a marine batt box now with deep cycle group 27 (I think). Big and heavy. Was fine in the truck but I'd like to shrink it for the Outback. Will probably go to a Yeti 400 Lithium with a solar panel.