Truck Fridge/Solar/Lithium Battery Issue

[arctictraveller]

Originally Posted by luked

I appreciate everyone's input, and honestly feel like I wasted some of your time. I will post an update once I swap the parts.

Not at all, no ones time was wasted. I suspected the thermostat, and by methodically trouble shooting, you seem to have come up with a reasonable solution. That's way better than randomly throwing parts at the problem. Good luck.................

[Merton]

I am afraid I will not be any help here but I had a similar problem on and off for about a year. I had two frigs, an upright Norcold that used AC when on shore power and DC when not and a DC only Norcold that loaded from the top. My problem may have been low voltage because at night I would hear the condenser on the upright cut on and then cut off all night. Very annoying! I tried running the power wires from both units directly to my house batteries but the problem would come and go and I could never figure it out. I now am using two Norcolds that load from the top and use only DC power. They are working perfectly (knock on wood). Sorry I couldn’t be more help but can only commiserate with you.

[jumpshowhigh]

Need to monitor the voltage at the input of the fridge when the compressor cycles up. If the voltage drop drops below the cutoff for the compressor to turn over, you'll need to increase the cable cross-section size to counter the voltage drop.

[jonyjoe101]

I had similar problem with my joytutu 26L 12 volt fridge powered by my 220ah lifepo4.
The problem with the compressor starting and then shutting off then recycling every few minutes usually occured at night time after the battery stop charging from solar. The fridge gave a code of E1. Eventually when I went to sleep the fridge would finally run without problem.
To fix I used a boost/buck converter set to 13.4 volts 6 amps output. The boost converter boost voltage to 18 volts, then its connected to buck converter that drop voltage to 13.4 volts. This fixed the problem and now I run the fridge through the boost/buck 24/7. This will also work with the lower voltage powerpacks, I tested with a 10.8 volt 26ah li-ion pack and it ran all night without problem.
The fridge needs stable power without too much voltage drop, from the boost buck converter the voltage only drops .2 volts from 13.4 to 13.2 when running. Even with the lifepo4 powering fans/laptops/etc, the power on the converter remains stable.

[86Scotty]

If your TF is starting up/stopping all the time it's under voltage. Bigger wires straight to batteries. They do not like small wires. I run 10 gauge wires from the plug on the back of the fridge straight to battery. You can try this without permanently wiring it that way to see if it solves it. Remember to fuse properly.

[jonyjoe101]

I have 10 and 12 gauge wire from the lifepo4 to all my accessories. And I actually connected the fridge directly from the lifepo4 to the fridge to minimized the wire length but that didnt help.

On my boost/buck converter i'm using wire gauge as low as 18 gauge(pure copper) on the output side that goes to the fridge, the 18 gauge is solder to 12 gauge (pure copper) that has an xt60 plug and that is connected to the fridge wire (xt60 connector) .
The reason I settled on 13.4 volts as the output voltage was because I tried 12.6 volts first but that was unreliable and was causing the same problem with the compressor. But at 13.4 volts even using 12 gauge wire has worked excellent. The fridge needs the higher voltage to work at peak performance.
This is a simple fix that doesn't require rewiring to higher gauge which might or might not work.


Here is picture of boost/buck converter while running fridge, only drops .2 volts during operation

[Scalf77]

Not sure about the joytutu 26L 12 volt fridge, but assuming that it uses the standard Seacop controller, the default cut-out voltage is 10.4 volts, and the cut-in voltage is 11.7 volts. This can be changed by changing the resistance between the C & P terminals on the controller. This would be in the harness from thermostat to the controller. I would generally check the connections from the thermostat to controller.

While the boost/buck converter solution is neat, it appears to be just covering up something that is broken not necessarily a design defect. It also uses additional power from the conversion process to do this.

I also still highly recommend adding a LED across the + fan connection and the D/I terminal. Take advantage of the diagnostic capabilities of the controller.

I have also found these two upgrades to be worth the looking into. The first is call the Merlin-II , mini smart speed controller

Merlin II performs four vital functions by controlling compressor speed;
1. Protects electronics from overload at start-up using a warm-start ramp-up routine.
2. Selects the slowest possible compressor speed for maximum system efficiency.
3. Ensures that maximum speed, and hence full system capacity, is utilized when required.
4. Gives visual indication of thermostat status, compressor speed, and compressor fault alarms

My only nit on the unit would be that the LED for errors and speed are on the board and thus not generally visible while installed and running in the van.

The second upgrade that I find useful if you want to know the temp of your fridge is the Coastal MK3 Digital Thermostat. You could certainly find a cheaper digital thermostat, but this does include the wiring harness. This unit will work well , with the Merlin-II and another plus is the fault LED is visible on the panel.

-greg

[86Scotty]

Dang Greg, that's sweet but not cheap!

[Scalf77]

Originally Posted by 86Scotty

Dang Greg, that's sweet but not cheap!

Eric, you are correct. The Merlin certainly does save some energy, you might remember that I had my old van heavily instrumented, and have lots of excel sheets showing the reduces current at the lower RPM speeds. The digital thermostat is nice if you leave the fridge running while parked in the house between trips. Essentially, you're not there to turn the dial down at night and turn it up during the day. Or maybe your just tired of doing that. The temperature display can be enlightening, and scary as you see the real internal temperature of the unit.

In any case if you take your saving from going to Truck Fridge add these you will still come in around the cost of a Isotherm unit with out the features.

I should also point out that Isotherm now sells an ITC Digital Display Intelligent Temperature Control. I have not tried this unit, but it sounds better than the Isotherm Smart Energy Controller, which I found to be a piece of junk. The ITC unit sounds like it has promise but requires that your fridge has the Seacop 101N0212 controller versus the 101N0200 or 101N0210. People purchasing new units may find that they have 101N0212.

-greg

[jonyjoe101]

When you mention power usage of the boost/buck converter I was actually able to test it.

I been running my fridge at 16f all summer (about 18 to 24 ah per 24 hours) I recently decided because Of cloudy conditions to raise the fridge temp to 26f. I raise the temp on thursday at 6pm, on sunday at 6am (2.5 days) the compresser hasn't run even once, temp in the fridge is about 27f. (compressor won't run until the temp reaches about 30f). The fridge seems to be able to keep the cold inside for several days without the compressor.

I have a dc wattmeter connected before the boost/buck converter, it shows a total of 5 amps used in the prior 2.5 days, thats from the fridge electronics, and the boost/buck converter (on the converter the 80mm fan is the power hog running constantly)

I also wondered if it was an efficient method to run the fridge, and it seems to be, it uses about 60ma per hour as per dc wattmeter (most of that is the fan).