Dual battery setup for a fridge

wandererr

Adventurer
I recently picked up a bodega 48 qt fridge and have been testing it in the garage. So far so good: it seems to be keeping temp as set (I'm using fridge thermometers to double check) and when you throw water bottles into the freezer, it pulls an Elsa on them and freezes them without any issues.

This takes me to the next step: how to keep it happy power wise. The specs state that the current draw on DC is between 1.5 nd 6 amps. I was originally going to do a dual battery setup under the hood with two group 34s till i realized I figured out what's the biggest honking battery that I could cram in there. I have an 80AH battery but no room to maneuver or even dream of setting up a second. Also I don't feel like pulling that one out just to put a second one in there.

So I'm scratching my head trying to come up with some alternative ideas as to placement and size of the fridge battery. I do have some limitations:

Fridge will be behind the narrow part of the back seat. The wide part of the back seat will be free so that it can lay down for a sleeping spot for our daughter when we take her with us on a trip (we'll be sleeping in the ursa minor top once we get to pick it up).

Btw, I have a solar setup that will allow me to keep the battery topped off during a sunny day.

Also it would be nice if the battery was easily accessible to be able to pull it out and eave the fridge behind if i wanted to.

Lastly: those of you with fridges (from what I can tell my fridge has similar draw to the ARB one) which battery you use for it and how long does it last on the battery before it gets too low (I know that the outside temps and how often you peek in there contribute to that but a starting point would be nice).
 

jscherb

Expedition Leader
Have you looked at the battery tray from moryde? It sits on the rear wheel well of the jeep. https://www.retrofitoffroad.com/shop/jk-jeep-wrangler-2007-2015/morryde-ammo-can-carrier-jp54-030/
That's what I use (how could I use anything else? I designed the tray for MORryde :))



I switched from the hard battery box top to a soft cover sewed from soft top fabric and includes Molle attachments:



The kitchen battery is wired so that when the Jeep is running the kitchen battery gets charged by the Jeep; when the Jeep is shut off there's no connection between the Jeep battery and the kitchen battery so the Jeep battery so there's never any danger of the fridge discharging the main Jeep battery.

The MORryde Trail Kitchen fits right alongside the battery.

 

skyfree

Active member
Not a Jeep, but I run my Indel-B + Lights + Fan + charge stuff on a 50ah LiFePO4 battery in this box, which is approx 15" X 9" X 9". It should fit in most vehicles easily:


This battery fits in the box:

This charger fits in there too:

The most power I've used between charges thus far has been about 20 amp-hours. It's plenty for a house battery in a vehicle.

IMG_0089.jpgIMG_0088.jpg
 
THIS is for a JL, but I think they were making one for a JK as well. I am intrigued by the use of the floor cubby. It also would not be difficult to fab something up for this are yourself for this purpose.
 

wandererr

Adventurer
All good ideas - thanks. Btw I love the idea of the lithium ion battery but holy moses... It's double what I paid for the fridge!
 

jscherb

Expedition Leader
All good ideas - thanks. Btw I love the idea of the lithium ion battery but holy moses... It's double what I paid for the fridge!
You probably wouldn't be happy with a 50ah battery for a fridge, Lithium or any other type. With a typical fridge drawing 4 amps or so, on a hot day when the fridge runs almost constantly you may be out of battery in the evening if you leave in the morning with a fully charged battery unless the second battery is connected to the Jeep's charging system and can be charged when the Jeep is running. If the battery is fully charged when you set up camp in the evening you maybe out of battery by the morning if you camp overnight in warm weather.

I use a marine/RV deep cycle battery from Walmart, it's 110ah and cost about a hundred bucks. It's good for a weekend in the wild even with the Jeep not running except in the hottest weather, and if I'm doing trails or something during the day it's good indefinitely because it'll be fully charged before setting up camp each night.
 

wandererr

Adventurer
I found an old (as in failing) battery in my garage, hooked it up to my solar charger (100W) and hooked up the fridge. As far as I can tell the fridge runs almost exclusively on solar at this point.

I'll see what happens over night. Btw, the battery I am using is group size 35, so that means it's between 40 and 60Ah.
 

jscherb

Expedition Leader
I found an old (as in failing) battery in my garage, hooked it up to my solar charger (100W) and hooked up the fridge. As far as I can tell the fridge runs almost exclusively on solar at this point.

I'll see what happens over night. Btw, the battery I am using is group size 35, so that means it's between 40 and 60Ah.
A 100w solar panel, if it's delivering a true 100watts (bright sun) is theoretically capable of delivering 8.3 amps at 12 volts, which is more than the fridge will ever draw.

You probably know this formula but just in case someone doesn't:

Power (watts) = Voltage * Current (amps)

So 100 = 12 * i -> 100/12 = i -> i = 8.33

Probably will deliver a bit less due to various losses but in any case in bright sun will deliver more than the fridge needs.
 

wandererr

Adventurer
A 100w solar panel, if it's delivering a true 100watts (bright sun) is theoretically capable of delivering 8.3 amps at 12 volts, which is more than the fridge will ever draw.

You probably know this formula but just in case someone doesn't:

Power (watts) = Voltage * Current (amps)

So 100 = 12 * i -> 100/12 = i -> i = 8.33

Probably will deliver a bit less due to various losses but in any case in bright sun will deliver more than the fridge needs.
I'm in SoCal and my driveway has perfect sun exposure: I do realize though that when I go camping I can't always expect perfect exposure.

So the way I see it: the battery gets charged in the vehicle while I'm driving. When I am parked, I throw the solar panel on the roof and keep the battery topped off (downside is that instead of parking in shade I will be looking for a full exposure parking spot).

Only time it's going to be 100% battery is at night.
 

jscherb

Expedition Leader
I'm in SoCal and my driveway has perfect sun exposure: I do realize though that when I go camping I can't always expect perfect exposure.

So the way I see it: the battery gets charged in the vehicle while I'm driving. When I am parked, I throw the solar panel on the roof and keep the battery topped off (downside is that instead of parking in shade I will be looking for a full exposure parking spot).

Only time it's going to be 100% battery is at night.
The way to figure how much battery you need is to do another calculation. First decide how long you need to run on battery overnight, let's assume 12 hours for the purpose of this example.

Then multiply the number of hours * 5 amps (assuming 5a is the max your fridge will draw), so 12 * 5 = 60 amp/hours.

That's assuming the fridge runs continuously at max amperage (camping in the Mojave perhaps?) so in less extreme conditions a 60ah battery would provide adequate reserve for overnight use.

But you also need to think about recharging the battery. Your solar charger should be able to power the fridge and provide a few amps to charge the battery at the same time, but a battery that's discharged to the point where the fridge shuts down may take up to 30 amps for a while when it starts charging. Depending on conditions (how hot it was overnight so how drained the battery got) and how much the fridge runs during the day, it may be that there isn't enough extra current available from the solar charger to run the fridge during the day and fully charge the battery at the same time.

A way to charge the fridge battery from the alternator is a good insurance policy for longer camping trips (especially for cloudy days, which I know you never get in SoCal :)).

Stop me if you know all of this already.
 

wandererr

Adventurer
A way to charge the fridge battery from the alternator is a good insurance policy for longer camping trips (especially for cloudy days, which I know you never get in SoCal :))
Hence as I stated - while in vehicle the battery gets charged as I'm driving ;)
 

Alloy

Well-known member
Not a Jeep, but I run my Indel-B + Lights + Fan + charge stuff on a 50ah LiFePO4 battery in this box, which is approx 15" X 9" X 9". It should fit in most vehicles easily:


This battery fits in the box:

This charger fits in there too:

The most power I've used between charges thus far has been about 20 amp-hours. It's plenty for a house battery in a vehicle.

View attachment 655568View attachment 655567
Those terminals on the charger look like the start of a problem
 

skyfree

Active member
Those terminals on the charger look like the start of a problem
Agree. I didn't have the right size hole version copper connectors when I built it. It's on my list of things to do over. Worst thing that can happen is it comes off, shorts and blows the massive fuse I have where it connects to the truck battery, and doesn't charge. I don't think it will though.
 

skyfree

Active member
You probably wouldn't be happy with a 50ah battery for a fridge, Lithium or any other type. With a typical fridge drawing 4 amps or so...
I guess it depends on how hot the environment is and what you have the fridge temp set to. I run mine at 34F and it never runs for more than a few minutes an hour, but I have never camped in above 85F temps. At night it comes on really infrequently. 50ah has been about twice what I actually need, which is a good margin for error. Looks like we need a study though, at different temps!

My setup is for minimal weight. No way am I going to lug around more battery than I need, and I went lithium to save lbs.
 
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