Dometic only runs off solar not Battle borns?

[ahh_me2]

"Plugged in, I get 14.6. In solar, 13.4 at high noon."
That is simply the charging voltage, not the actual voltage of the battery

"It seems like I should figure out a way to plug the fridge directly into the inverter, yes?"
The inverter will add a bit of loss to the system, so the fridge would most likely cut out even sooner.

 

[jonyjoe303]

this is the tk15 couloumbmeter I been using on my lifepo4. Once the battery is fully charged to 100 percent 14.4 volts, it starts counting amps in/out. It no longer relies on voltage to determine SOC. The shunt (which measures the amps) is connected near the battery terminals, thats why these are very accurate.
Victron also makes a coulomb meter.
If your batteries are connected in parallel, they will both be the same voltage all the time. Once connected together, they equalize to the same voltage. If one is undercharged, they both will be undercharged. My 220ah lifepo4 battery is 2x 110ah lifepo4 batteries connected in parallel.

 

[LoupGarou]

Does the Dometic not have a AC power input and power cord? If it does, power the Dometic via the inverter 120vac output.

 

[frater secessus]

When you say that there is a voltage drop of around a volt or so when powering off the batteries, this is an indicator that your batteries are not capable of putting out enough current.
This means either the batteries are not fully charged, or they are weak

Or there is sag from resistance in wiring/connectors, or something is causing the compressor to draw outsized current, etc...

 

[frater secessus]

The volts on my display shows how much charge I'm getting from my panels. Out here in Quartzsite, 13.4 is the most I've gotten. If I don't use anything, it will read13.2-13.4 over night. When the compressor turns on, that 13.4 or 13.2 will drop to 12.4/12.2. As the night goes on, it might drop to 13 0 so now when the compressor kicks on, it drops to 12.0 and shuts off.

Got it, thanks for the explanation.

Why is this so hard?

Troubleshooting can get complex when there are many components and no one but the installer knows how it's all put together. We make guesses and suggest tests that help narrow the possibilities. We'll get there.

 

[MotorVation]

This isn't directly related to the battery charging issue but if that Dometic is using a cigarette lighter type plug into a cigarette plug port, there will be a voltage drop, especially when the compressor starts. This isn't my opinion, my Whynter had one of those plugs. I cut it off and wired it directly to the batteries with ring terminals.

The Dometic should have a way to raise or lower the low voltage disconnect set point. It will be in the owners manual if so.

Also, I have 590 watts of solar on the roof and with the weather being what it's been around Quartzsite, there are days when my batteries (2xBattleborn) aren't getting the full absorption cycle I set my charge controller to. (30 minutes per battery @14.4 volts). Yesterday was one of those days and today is getting iffy. I may run my generator for a while later on

 

[MotorVation]

Dometic manual

Above, I've put a link to the manual for your fridge. It does have an adjustable low voltage shut down. Please see section 7.4 for the info to adjust it lower.

I would put it on low. Your fridge wiring is causing the voltage drop most likely and if you adjust the low voltage shutoff setpoint lower, it's not going to harm your batteries. They're protected by the BMS built into them. This may keep your fridge from shutting off.

If I were a gambling man I would bet that it's set to 'high.' There is a low, medium, and high setting

 

[DannyB1954]

Many 12 volt refrigerators come with a cord that plugs into a cigar lighter. The is one place for a bad connection to happen. If not already done, you can wire it to the battery through a suitable fuse and it might help. I also increase the wire size when I do this. The smaller the wire, the more electrical resistance it will have. This creates a voltage drop and the compressor will use more amps to compensate.

 

[Calaverasgrande]

I have a Setpower compressor fridge of similar size.
It runs off my LiFePo4 battery bank.
The way my stuff is hooked up, and I followed standard diagrams, is that the charge controller, batteries and DC outputs are all hooked up in parallel.
Just imagine 2 big posts.
One red, one black.
Everything is tied to those posts. So in theory if enough amps are coming in from the charger, the batteries aren't getting touched by the amperage draw of the fridge. Likewise for the roof fan, internal and external lights etc.
In reality the wiring of my system doesn't all just terminate to two big posts.
It's topologically more complicated. But in terms of electrical circuits thats how it works.
I'm actually going to redo it to a couple of big buss bars for Neg and Pos before I expand my battery bank further.

Also, my budget friendly Setpower compressor fridge has setting for low voltage sensitivity.
Low Med and High.
The idea being you set the sensitivity to high if you are running on your starter battery.
You set it to low if you have separate house battery and starter battery.
That way if I was running off my starter battery and it drained until it was only giving 11.6V or something, then the fridge stops pulling.
I don't care if it drains my LiFePo4 bank to death, so I have it on the lowest setting.
It never gets close though. I drive every day and my bank is always at or near 100% unless I am camping out for a couple days in a camp ground.
Need to finish doing a shore power hookup on mine for that!