Truck Fridge/Solar/Lithium Battery Issue

[luked]

I have a strange problem with my truck fridge that has been paguing me for a while. I have spoke with truck fridge, they were baffled and they have not been any help. The fridge holds temp and so I've just been living with it.

Current setup is

350w solar
zamp dual battery controller
battle born 100w lithium
battery separator relay (connects van charging system when ignition on)
truck fridge TF130 AC/DC model

Issue: the fridge compressor cycles on and off randomly. It wramps up and immediately shuts off, over and over again. While somewhat random, it seems to be doing it more often during the day when on solar but will also do it at night with no sun. It will also do it when we are driving and the separator is conencted to the van electrical sysem so the alternator is charging the lithium battery. I have disconnectd the separator to eliminate the issue but it does the same even when disconnected.

The only time it does not do it is when I plug the fridge in to AC and when I hook my battery charger up to the litium battery.

The fridge has no problem holding temp and all other 12v accessories work (water pump, lights, etc)

I mean, it's not a complicated setup. I have checked every wire (there are only 2!). Truck fridge said I could try replacing the thermostat but if it works on AC and a battery charger that seems to rule that out as an issue.

I wonder if it's some sort of weird charging pulse the fridge doesn't like, maybe a 5a diode could help? IDK, any ideas?

[Mr.Anderson]

That is an odd problem, do you have an inverter in your rig that you can just run off the AC mode of the fridge? Granted you'll have an efficiency loss from the inverter but if it improves fridge operation maybe it's worth it?



There should be a temperature feedback loop on the compressor of the refrigerator that tells the compressor to turn on when a set point temperature high limit is reached (such as 45 degrees) and then tells the compressor to turn off when the low limit is reached (such as 35 degrees). If it's sporadically turning on an off it could be that those limits are too close to each other (picture high limit of 40, low limit of 39) but you would still have a somewhat normal timescale to that behavior based on ambient temperature and how fast the fridge interior warms up.



I wouldn't see why that circuit which controls the temperature control feedback loop would behave differently based on AC vs DC, but maybe there are two controllers one for the AC mode and one for the DC mode and the DC controller has gone bad - that's at least one question I would ask truckfridge.

[luked]

Thanks Mr. Anderson for your reply. I am not running an inverter. If I hook up my 12v battery charger to the lithium battery the fridge doesn't exhibit the behavior, so as long as I supply a constant supply of power through AC or through a 12v charger it seems to behave.

I think I am going to unhook the solar charge controller and see what happens. It is currently set for 90% to the house batteries (using a lithium charge profile) and 10% to the van starter batteries (lead acid profile). I'm just out of ideas

I should also note, since installing the fridge in the summer of 2017 it has not been shut off. I keep it loaded with water and sodas, bags of ice in the freezer and the solar keeps up with it with no problem and it keeps a nice temperature. But some nights camping it will just cycle and cycle, ramp up and down up and down, it doesn't seem matter what the ambient temperature is.

[Scalf77]

Did truckfridge have hook a LED across the positive connection and the D/I terminal, this will give you a LED fault code, it will be in the form of flashes:

0 = No error
1 = Voltage failure
2 = Fan failure
3 = Motor failure
4 = Speed failure
5 = Thermal failure

If there is no flashing the issue is probable related to power, issue with the controller, or thermostat.

What size wires do you have going to the unit, is the ground connection good? What voltage does your battery charger put it at when you plug it in, what voltage do you get when solar is charging, what voltage do you get when the separator is charging from alt.

I would expect the unit to fail more during the day, as it would cycle more often then at night. If you want to eliminate the thermostat to test, just put a switch across C & T terminals.

My 20,000 ft assessment would low voltage caused by a bad connection.

-greg

[Mr.Anderson]

OK if it's happy with a constant 12V supply, how is the fridge connected? I take it it's connected to the 12V lithium battery, but the charge controller might be diverting some of that to the starter battery. That makes me think that maybe the starter battery is going bad and pulling too much juice from the aux Li battery when not driving? Removing the charge controller from the equation might help identifying the source of the issue: it sounds like it's less to do with the Fridge and more to do with the source of power. If you haven't tried that already, maybe even just disconnect the charge controller from the starter battery and see if the compressor cycle goes back to normal when its running only off the lithium battery.

[IanF]

I agree with Greg - sounds like a symptom of under-voltage. This usually happens due to undersized wiring that causes the voltage to drop under load. Is there enough play in the wiring to get a volt meter on the input terminals of the fridge while it's running?

Looking at the Truckfridge website, the TF130 can pull over 33A at 12V. The wiring should be #8 AWG minimum.

[JWA]

As a WAG how old is this Truckfridge? Could it possibly be suffering from a loss of refrigerant charge causing these issues?

[arctictraveller]

Trouble shooting pretty much anything is best started with the basics like pressure, flow, voltage, current draw etc. In your case, knowing the voltage right at the refer under load (while running) is important. I am going to guess you are suffering from low voltage under load. If it's low, from there you can work your way backwards, taking measurements along the way to see where the voltage drop is occurring. When on shore power, the voltage is probably higher. Once you have those numbers, get back to us................

[luked]

Well, I spent the better part of 3 hours late last night going through my wiring and testing various scenarios( I really should have made my wiring panel easier to access ). In the end, after isolating it from everything, using another battery, and even plugging into AC (again) I removed the fridge from 12v entirely and left it plugged in to an AC extension cord (I've done this before so many times!!), it took about 30 minutes but it started exhibiting the ramp-up/down even while just on AC.

I called truck fridge today and they said it could be the controller and/or thermostat and were sending me replacement parts.

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.

[luked]

Originally Posted by JWA

As a WAG how old is this Truckfridge? Could it possibly be suffering from a loss of refrigerant charge causing these issues?

Bought in July 2017, darn thing has been running since then. It's been a great fridge with this annoying problem for the last year or so. If I used my van more often I would have tried addressing this sooner :-(