Fridge Run-times / Small Dual Battery Build

[Bumbo]

For all you fridge/freezer people… Have you metered the power to see the true amount consumed?

For the ARB 50, the spec sheet shows 7 amps as it’s max load, but it’s generally closer to 4-5 amps at fridge temps and can be lower (3.5 to 4 amps) after reaching temp. It also does not run 100% duty cycle (continuous) so whatever power its consuming needs to be averaged across its off-cycles. I think it’s worth mentioning that at 24 volts it’s about 15% more efficient than at 12.

Generally when I am camping it’s about half a day until the truck gets turned on again, I would like to build the smallest dual battery setup that would last about half a day… if I really needed more, I could supplement charge via alternator or solar.

Even for running this thing in the city for grocery shopping and errands the requirements for time would be even less. I generally turn it on right before I leave and it gets to temp by the time I need it...

How long do you guys generally run your fridges without throwing charge back into them?

 

[Jeremy556]

For half a day, the stock battery will be fine.

It is all highly dependant upon contents, ambient temp, etc. but my Odyssey group 24 will keep my ARB at 31c half full of beer and water for about 2 days in 100f ambient temps in blazing sun. My old 31 would last about 3 days under the same conditions.

Day to day, I have a shore power cord I plug in that powers the 110v circuit of the ARB and a 12v charger for the battery that keeps the AGM happy.

 

[Isais101]

I had the same question a few weeks ago that have a dometic 35 L and wanted to see what was an alternative to a dual battery did some research and came up with upgrading battery I ended up with a NorthStar 27f got it in the mail yesterday installing it last night hooked the fridge last night been connected 24 hours with SoCal temps and I just went to check if battery was dead by starting truck and nope started right up

 

[wcjeep]

You may have to test at home. You listed some variables. Are the groceries going into the cooler already cold? How often accessed? Ambient temp?

I run the freezer at 20deg F or colder. This makes the fridge area around 38deg F. Again, varies depending on what's inside. If it's going to be off for a bit I run the freezer at 0deg F. Also coat the freezer area with blue ice. This allows it to last a bit longer without power. I have an older ARB. I place a cheap wireless thermometer remote sensor inside.

 

[jhguth]

1A is a good rule of thumb average for fridge with duty cycle factored in, most good fridges are 0.7-1A average

I run my fridge 24/7, i keep stuff for lunch and drinks and use it to go grocery shopping at lunch

I have not trended amperage (i want to get a shunt to monitor all this but they aren't cheap), but my cheap battery monitor trends voltage and i can see when the fridge turns on and off from the voltage change due to the load when the engine is off.

For half a day you really don't need a dual battery, but replacing your battery with an AGM is a good idea simply for the health of the battery (stock battery isn't intended to deep cycle). If this is a rare occasion thing the stock battery will be fine though. Running my fridge 24/7 I started seeing poor performance on my stock battery after about 6 months.

Just replace your battery with a 24m battery, it will fit in the stock location (stock is group 24) without any changes and a 24m battery will typically have about a 75Ah capacity which will more than meet your half day requirement (probably good for a day and a half in good conditions). You can get a voltage booster diode on ebay for about $15, that will help it charge properly

My 31m battery lasts about 3 days in good conditions (temps not too crazy, full fridge) and into day 2 in poor conditions (hot temps, half full fridge) on the highest voltage shutoff setting

 

[jhguth]

Also, I'm using this cheap wireless thermometer to monitor temps. I have one sensor in the fridge part, one on the little tray thing above the compressor, and it also monitors vehicle interior temps. It records the max and min temp so I can check if the fridge got too warm.

$18:
https://www.amazon.com/gp/product/B078BRM9QG/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

 

[SlickTRD]

I had the same question a few weeks ago that have a dometic 35 L and wanted to see what was an alternative to a dual battery did some research and came up with upgrading battery I ended up with a NorthStar 27f got it in the mail yesterday installing it last night hooked the fridge last night been connected 24 hours with SoCal temps and I just went to check if battery was dead by starting truck and nope started right up

Did you need to do anything to make the 27F fit?

 

[jhguth]

31m is basically the same footprint as 27 just taller and 110ish Ah vs 90ish Ah. You might want to get a metal tray since they are longer than stock.

 

[Tuc4R]

Did you need to do anything to make the 27F fit?

You have to get a new battery tray. I got this one.
https://www.makariosrv.com/noco-gro...MI2-PVuMOS3QIVjf5kCh3wZwfGEAQYASABEgJuSfD_BwE

 

[Tuc4R]

If you do go with an AGM, you will need to do some battery maintenance. The stock alternator will not charge an AGM battery all the way. You will need to charge it at home with a proper charger.
This is the one I got.

https://www.amazon.com/NOCO-G7200-U...ns&keywords=noco+genius+battery+charger&psc=1

 

[SlickTRD]

You have to get a new battery tray. I got this one.
https://www.makariosrv.com/noco-gro...MI2-PVuMOS3QIVjf5kCh3wZwfGEAQYASABEgJuSfD_BwE

Thanks! Does the factory J-hook and battery tie down work with this tray or did you use the provided straps?

 

[Tuc4R]

Thanks! Does the factory J-hook and battery tie down work with this tray or did you use the provided straps?

That I don't know yet, I just ordered it yesterday. lol I was just going to figure it out when it comes in.

 

[Isais101]

Thanks! Does the factory J-hook and battery tie down work with this tray or did you use the provided straps?

Just a bigger battery tray even the stock j hooks work for this battery

And wires is plug a play

 

[Isais101]

This are items I used for NorthStar 27f and 12v plug I installed in rear of truck

I ordered the battery from GP audio website I got the NorthStar 27f for $280 delivered to front door

 

[puckitpuck]

I had the same question a few weeks ago that have a dometic 35 L and wanted to see what was an alternative to a dual battery did some research and came up with upgrading battery I ended up with a NorthStar 27f got it in the mail yesterday installing it last night hooked the fridge last night been connected 24 hours with SoCal temps and I just went to check if battery was dead by starting truck and nope started right up

What do you call that component next to the Aircomp? fuse tray? Electrical panel? I think I need that. Your seems very clean.

Your air comp is use for airlocker and tire inflation?

I got REDARC BCDC1225D in the box ready to install. I need to figure out the wiring, type and size of 2nd battery to connect with 100W solar panel and starter battery/alternator.
Planning to power Dometic 65 and other small stuffs.

 

[Isais101]

What do you call that component next to the Aircomp? fuse tray? Electrical panel? I think I need that. Your seems very clean.

Your air comp is use for airlocker and tire inflation?

I got REDARC BCDC1225D in the box ready to install. I need to figure out the wiring, type and size of 2nd battery to connect with 100W solar panel and starter battery/alternator.
Planning to power Dometic 65 and other small stuffs.

Blue seas 6 fuse box I have air compressor for tires only but if I wanted to I can put air lockers with it and also a 100 amp fuse breaker that’s on top of my stock fuse box

 

[Bumbo]

I did a bunch of testing and at this point I think I am going to go small... as small as possible to run 1/2 day 100% duty cycle.

I want this to be 100% plug and play to run only off the existing outlets already in the cargo area.

This is where I am at so far... I might even consider building it into a drawer system or something.

 

[jhguth]

I did a bunch of testing and at this point I think I am going to go small... as small as possible to run 1/2 day 100% duty cycle.

I want this to be 100% plug and play to run only off the existing outlets already in the cargo area.

This is where I am at so far... I might even consider building it into a drawer system or something.

100% duty cycle? Are you running it with the lid off? Half day 100% duty cycle is over 60Ah, that's more than 2 days usage at a typical duty cycle

Dont use the plug in the rear, there is too much voltage drop which will make the fridge shutoff prematurely because of the voltage protect. It takes like 10 minutes to run dedicated 12v power to the back and requires no drilling or damaging of anything. You can buy the ARB kit if you're unsure about making the wires yourself, it has everything you need.

 

[Bumbo]

100% duty cycle? Are you running it with the lid off? Half day 100% duty cycle is over 60Ah, that's more than 2 days usage at a typical duty cycle

Dont use the plug in the rear, there is too much voltage drop which will make the fridge shutoff prematurely because of the voltage protect. It takes like 10 minutes to run dedicated 12v power to the back and requires no drilling or damaging of anything. You can buy the ARB kit if you're unsure about making the wires yourself, it has everything you need.

I think you might be misunderstanding what I was trying to say...

100% duty cycle meaning the battery will have enough capacity to run the fridge continuously for that duration, not that it will

In real world use, it will be closer to 50% duty cycle depending on loading and ambient temp.

If it can run 12 hours 100%, it can run 24 hours 50% duty cycle.

This is also a "24 volt" battery... meaning you need half the Ah to do the same job of a 12 volt battery, and the fridge runs more efficiently at 24 volts by about 15%.

I don't have to worry about voltage drop of the rear 12v outlet because it's not running the fridge, only charging the batteries using a 12 to 24v DC to DC charger.

And I am actually on the opposite end of unsure about wiring... I have two other trucks with dual batteries setups. One of them being a 4th Gen which is my off-road truck and where the fridge has usually sits.

I just felt like doing something different in the 5th Gen just for fun, consider the last video proof of concept.

 

[Tuc4R]

I decided to go with X2 Power 27F and a Renogy 100W solar suitcase. As long as I have decent light, I can run indefinitely. Worked great camping the last 2 1/2 days.