Dometic CFX misbehaving and fix, a lesson in really thinking your wiring through.

[clarkhogan]

Dometic CFX95 refrigerator in a '20 jeep gladiator rubi in the bed (under a cap).

I was chasing my tail for months on what I thought were bad thermistors, failing compressor, bad logic board or anything really. Have a dedicated low gauge power line running from battery system to the bed. Odd symptoms, funky behavior, sometimes cold sometimes not, freezing my milk while melting my ice cream out on the campsite (how did we ever survive), the disturbing concerning "compressor system faulty" error in the app after my warranty has expired. Replaced the thermistors. Still no joy. Considered going to a repair dealer or short circuiting somehow the dometic on board battery protection systems or buying a new fridge. (both batteries in the truck were replaced 4 months ago.)

Facepalm, most modern vehicles run the "house power" off of the stop start battery. Which runs substantially less amperage than the main battery. There is an intelligent battery sensor under the ground terminal on the main battery which disconnects it most of the time. So even if you think you have your fancy fridge hooked up to the hot big battery terminal and well grounded to the frame or the big battery negative, its not drawing that battery, its drawing the small start stop battery. Which is not enough to even maintain the fridge at 36 degrees (because the dometic battery protection system is doing its job). Which is obvious to me now but didn't think about it before. Which also means I need to rewire the winch.

Turns out Dometic makes a damn fine fridge after all these months of cursing. Paying it forward and sharing this moment of facepalming, and prolly someone else has figured this out and posted but sharing anyway, and also no need to talk trash about the ESS, it's fine thanks.

Now I'm off to go order a dual battery system. :-D happy trails!

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[Jaxmax]

Hey beat yourself up al ya want you figured it out, that's what counts, Good job!! I have a fridge in the bed under a RSI cap and love it, never thought I would leave it in as much, can turn it on and off from my aux switces (Voswitch) and the dual battery system that disconnects the starter battery from house battery or visa /versa, also backs up the ARB fridge low power safety shutoff. Be careful it is a deep rabbit hole, I now have a 100watt solar panel on the cap that keeps both batteries fully charged.......Jack

 

[ShadowsPapa]

There is an intelligent battery sensor under the ground terminal on the main battery which disconnects it most of the time. So even if you think you have your fancy fridge hooked up to the hot big battery terminal and well grounded to the frame or the big battery negative, its not drawing that battery, its drawing the small start stop battery.

Lest anyone misunderstand this - that IBS doesn't disconnect anything. It's fully connected to the large battery at all times. Those of us with winches and other equipment always connect to chassis or the top of the IBS without issue.
You may have a defective IBS or had a bad connection - but it's not a switch and doesn't contain a switch. It's always connected because it's simply a copper shunt - not a switch.
It has no disconnect abilities.

 

[JTGuy]

I power my fridge off my Bluetti power pack that will run it for days. The Bluetti gets recharged off the truck when the engine is running. Aux power switch with wire run to the bed. That also gives me 1500 watts of 120V AC power. Stays separate from the Jeep electrically and can be moved into other vehicles when needed.

 

[clarkhogan]

Lest anyone misunderstand this - that IBS doesn't disconnect anything. It's fully connected to the large battery at all times. Those of us with winches and other equipment always connect to chassis or the top of the IBS without issue.
You may have a defective IBS or had a bad connection - but it's not a switch and doesn't contain a switch. It's always connected because it's simply a copper shunt - not a switch.
It has no disconnect abilities.

Yep you’re right. Now I have to rethink this again.

 

[Mr._Bill]

Yep you’re right. Now I have to rethink this again.

Here's a little more to think on. The two batteries (Main and Aux) are paralleled together all the time, except during the startup test and during ESS events. The fridge was never just running off the Aux battery. The most likely problem was the high parasitic draw of the truck, along with the draw of the fridge, caused the battery saver in the fridge to kick in sooner. As the batteries aged, the problem got worse.

The better solution is a separate battery for the accessories, and a DC/DC charger or Smart Isolator to connect it to the trucks electrical system. If you don't want to go that route and effort, a portable power station provides a similar solution. The Genesis dual battery setup is a decent solution, but you are putting in two smaller batteries and splitting the load between them.

 

[ttn333]

The better solution is a separate battery for the accessories, and a DC/DC charger or Smart Isolator to connect it to the trucks electrical system. If you don't want to go that route and effort, a portable power station provides a similar solution. The Genesis dual battery setup is a decent solution, but you are putting in two smaller batteries and splitting the load between them.

With the odd issues of the stock dual battery system, I find it prudent to separate my "house" battery from the truck. It's easy enough to run a solar panel (175w thin flexy for me) to a mppt or dc-dc mppt charger a 100ah lipo4 and have your fridge plugged in semi permanently. I actually just run an mppt solar charge controller and an ac-dc charger. I have both on hand and with ac-dc charger I can just plug it into the bed 120v receptacle in the bed and turn it on and off from the driver's seat. Most of the time, solar is all I need to keep lipo4 topped off.

 

[Mr._Bill]

With the odd issues of the stock dual battery system, I find it prudent to separate my "house" battery from the truck. It's easy enough to run a solar panel (175w thin flexy for me) to a mppt or dc-dc mppt charger a 100ah lipo4 and have your fridge plugged in semi permanently. I actually just run an mppt solar charge controller and an ac-dc charger. I have both on hand and with ac-dc charger I can just plug it into the bed 120v receptacle in the bed and turn it on and off from the driver's seat. Most of the time, solar is all I need to keep lipo4 topped off.

The stock dual battery setup is treated more as a single battery system, except during ESS events where the load is actually split between the batteries.

I have a separate (third) battery in the back to run accessories from. Solar would be nice. For now, it is connected using a Smart Isolator and is charged when the engine is running.

With the first truck, I used a portable power box that was charged by the 120v outlet in the bed. This truck doesn't have the bed outlet, so I put in a 12v port that connects to the rear battery. The fridge will run for a long time with this setup.

 

[clarkhogan]

Here's a little more to think on. The two batteries (Main and Aux) are paralleled together all the time, except during the startup test and during ESS events. The fridge was never just running off the Aux battery. The most likely problem was the high parasitic draw of the truck, along with the draw of the fridge, caused the battery saver in the fridge to kick in sooner. As the batteries aged, the problem got worse.

The better solution is a separate battery for the accessories, and a DC/DC charger or Smart Isolator to connect it to the trucks electrical system. If you don't want to go that route and effort, a portable power station provides a similar solution. The Genesis dual battery setup is a decent solution, but you are putting in two smaller batteries and splitting the load between them.

I watched a video last night talking about how Genesis is the wrong way to go now especially with lithium powered batteries, being cheaper, lighter, and better all around. What I can’t figure out is why if the jeeps battery power at voltmeter is at 12.61V with the engine off, doors locked, and all auxiliary and computer systems are off, the refrigerator exhibits these funky symptoms, but if I drag an optima battery out of the garage, freshly charged at 12.41 V and hook it up to the fridge it works perfectly.

A dual battery hooked up in parallel would have all the amperage required to drive this battery and Any functional parasitic losses would not account for this behavior as all of those systems are off when the jeep is locked and in a sleep cycle

The isolated power line I ran to the bed from the Jeep. Batteries are low gauge and plenty beefy enough to handle the current.

 

[Mr._Bill]

I watched a video last night talking about how Genesis is the wrong way to go now especially with lithium powered batteries, being cheaper, lighter, and better all around. What I can’t figure out is why if the jeeps battery power at voltmeter is at 12.61V with the engine off, doors locked, and all auxiliary and computer systems are off, the refrigerator exhibits these funky symptoms, but if I drag an optima battery out of the garage, freshly charged at 12.41 V and hook it up to the fridge it works perfectly.

A dual battery hooked up in parallel would have all the amperage required to drive this battery and Any functional parasitic losses would not account for this behavior as all of those systems are off when the jeep is locked and in a sleep cycle

The isolated power line I ran to the bed from the Jeep. Batteries are low gauge and plenty beefy enough to handle the current.

The Jeep computer systems never turn off. The AGM batteries in the JT should read 12.8 volts when fully charged with no load on them.

The average life expectancy of batteries in the JT is about three years. The factory batteries are not the highest quality or capacity. If they are not kept charged through regular driving, or use of a battery maintainer, they will lose capacity and die even sooner.

The charging system is designed for AGM batteries. Lithium are good for use as an accessory battery, but need to be coupled with a DC/DC charger.

 

[ShadowsPapa]

I watched a video last night talking about how Genesis is the wrong way to go now especially with lithium powered batteries, being cheaper, lighter, and better all around. What I can’t figure out is why if the jeeps battery power at voltmeter is at 12.61V with the engine off, doors locked, and all auxiliary and computer systems are off, the refrigerator exhibits these funky symptoms, but if I drag an optima battery out of the garage, freshly charged at 12.41 V and hook it up to the fridge it works perfectly.

A dual battery hooked up in parallel would have all the amperage required to drive this battery and Any functional parasitic losses would not account for this behavior as all of those systems are off when the jeep is locked and in a sleep cycle

The isolated power line I ran to the bed from the Jeep. Batteries are low gauge and plenty beefy enough to handle the current.

Be careful what you watch on videos. Lithium are fine for camping and fair weather things but not a battery you want as your truck's main battery - two reasons:
Cold weather performance drops off
and
the vehicles are made to deal with lead acid batteries - like AGM, not lithium.

A battery at 12.41 you say is freshly charged is not fully charged. AGM batteries should be over 12.7 volts for fully charged. In fact, after a proper charge with a good AGM charger - leaving it on for several hours to go through all 4 phases of charging, will actually read over 13.0 volts when you first take it off the charger. That's surface charge.
So if you have an Optima battery on a charger and it read only 12.41, it's going bad, or didn't take a charge. Optima batteries are all AGM - which means that one is going bad or your charger is not working correctly, or not an AGM charger.

As far as your Jeep - if it's reading 12.61 volts - it's not fully charged. After fully charging mine and disconnecting the charger and putting things away, I can go measure the voltage of my battery and still be 12.7+
Granted, after a few hours it will have dropped a bit, but it takes a while to get down to 12.6 volts - several hours.

If you drive your Jeep, park it, open the hood and measure 12.6 volts, it means that the batteries didn't get fully charged from your driving.

I didn't read the whole thing - where are you powering your fridge - and what size wiring is going to it?
It works with fridge connected directly to a battery (one that's low at 12.4 volts) but not in your vehicle - how do you have it wired and what size wire, types of connectors and so on?

My cheap Coleman cooler has a hefty draw, but works fine wired through my aux switches to an outlet in the back of the truck bed - which all runs off my truck batteries.

 

[Readyt]

Bill,
When you wired your bed what gauge wire did you use and did you put in an inline fuse? I know I saw a thread on it but cannot find it. Need to do mine this weekend
Ted

 

[clarkhogan]

fused with a heavy duty waterproof disconnect under the hood. Wire is gauge six if I recall correctly.

 

[clarkhogan]

Be careful what you watch on videos. Lithium are fine for camping and fair weather things but not a battery you want as your truck's main battery - two reasons:
Cold weather performance drops off
and
the vehicles are made to deal with lead acid batteries - like AGM, not lithium.

A battery at 12.41 you say is freshly charged is not fully charged. AGM batteries should be over 12.7 volts for fully charged. In fact, after a proper charge with a good AGM charger - leaving it on for several hours to go through all 4 phases of charging, will actually read over 13.0 volts when you first take it off the charger. That's surface charge.
So if you have an Optima battery on a charger and it read only 12.41, it's going bad, or didn't take a charge. Optima batteries are all AGM - which means that one is going bad or your charger is not working correctly, or not an AGM charger.

As far as your Jeep - if it's reading 12.61 volts - it's not fully charged. After fully charging mine and disconnecting the charger and putting things away, I can go measure the voltage of my battery and still be 12.7+
Granted, after a few hours it will have dropped a bit, but it takes a while to get down to 12.6 volts - several hours.

If you drive your Jeep, park it, open the hood and measure 12.6 volts, it means that the batteries didn't get fully charged from your driving.

I didn't read the whole thing - where are you powering your fridge - and what size wiring is going to it?
It works with fridge connected directly to a battery (one that's low at 12.4 volts) but not in your vehicle - how do you have it wired and what size wire, types of connectors and so on?

My cheap Coleman cooler has a hefty draw, but works fine wired through my aux switches to an outlet in the back of the truck bed - which all runs off my truck batteries.

There’s gauge two or four off of the battery to a bus bar off of which three heavy duty, marine, disconnects, or connected each of which route to various power services such as winch, bed, and compressor. From there, an in-line fuse, and then a higher gauge six wire routes through the frame to the bed where it terminates into a junction box with posts positive and negative. From there, I run one line to a relay for LEDs on the bed cab and the other to a cigarette lighter terminal for the cooler. I’m gonna check all these today for proper connectivity and resistance.

 

[Mr._Bill]

Bill,
When you wired your bed what gauge wire did you use and did you put in an inline fuse? I know I saw a thread on it but cannot find it. Need to do mine this weekend
Ted

I used a Warn cable to connect the rear battery to the Smart Isolator. There is a 300 Amp fuse on the battery side of the cable. There is a 200 Amp fuse on the battery side between the Main battery and the Isolator. The fuses are just to prevent a fire if the cables develop a short from wear or an accident. The disconnect for the winch is fed from the auxiliary battery side of the Isolator. I have never used the winch under load, so I can't say how well that actually works.

WARN 32963 20' Quick Connect Power Cable https://a.co/d/7SS9WxK

WARN 36080 Quick Connect Winch Power Cable for Vantage 4000, ProVantage 4500, and RT40 Winches, 28" Length https://a.co/d/4q93N03

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