Norcold Low Voltage Set Point

[NewmanRacing]

August of 2017 I installed a new Norcold NXA641.3 3 way fridge.

My AGM deep cycle battery is not new but is is by no means out of life. Fully charged I get 12.5 Volts.

The Norcold fridge shuts down with a low voltage code at 12.4 volts.

Is that actually the low voltage set point for these refrigerators? Can I adjust or over ride the low voltage set point?

The manual only states the low voltage set point exists. I can not get Norcold to answer the phone or email.

I would dislike replacing my battery just to satisfy this setting on the fridge.

 

[Henry J Fate]

I dont have the specification for the low voltage cut off but can say with reasonable certainty that 12.4 volts is not the designed cut off.

It could be a fault in the fridge but I would be more likely to assume that the voltage is dropping below 12 volts.

Use a digital meter at the connection to the fridge. That reading will be as accurate as you could easily attain and will measure it under load as the board cutoff does. Leave the meter connected and monitor what it does being concerned with voltage at the cut off point.

You may have a bad connection somewhere or even need to replace the battery.

 

[NewmanRacing]

That is what I was thinking. Seems too low but I have not been able to confirm. I did check voltage at the fridge main DC input and measured 12.4 volts after it cut off. The ground and + wiring is rock solid.

I will try to catch it in the act.

 

[Kevin Means]

I'm not famaliar with how that setting might be changed. Hopefully, someone here is. However, if your battery is indicating 12.5 volts when it is trully fully charged, there may be something wrong with it. That's only an 80% state of charge. A fully charged AGM should indicate 12.6 or 12.7 volts. That may not seem like much of a difference, but it is.

If there was a load on the battery when you measured its voltage, that could explain it, or whatever you're using to measure the voltage might not be accurate, but if 12.5 volts is an accurate indication of your battery's voltage when it's fully charged, there's a good chance that something is wrong with it.

Kev

 

[Gary RV_Wizard]

Agree with Kevin: something is wrong with your battery or there is a substantial load on it, because 12.5v is only about 80% of charge.  A voltage below 12.6 with no load indicates one of the 6 cells in the battery is not functioning properly and that usually results in a rapid loss of voltage as soon as any major load is applied. The 12v heater in your fridge is "major", probably near 20 amps.

I'm assuming this shutdown occurs when the RV 12v system is running from battery only. When it happens, is the fridge using its 12vdc mode heater or LP gas mode?  In LP gas mode, the fridge uses only a tiny amount of 12v power to operate its circuit board, but in 12v mode there is a substantial amp draw from the battery. A weak battery will quickly suffer a major drop in voltage that could trip the low voltage sensing circuit. As soon as the heater demand gets shut off, the battery voltage would recover and may well seem OK at that point. 

What shutdown code is displayed on the control panel? is it "dc LO" or "dc-HE"?

The circuit board is rated to operate as low as 10.5v, but the DC heater could be set to turn off well above that point so that it doesn't totally drain the battery and leave the entire RV without power.  The low voltage sense for the 12vdc power mode may be much higher than 10.5v and is not adjustable. If I had to guess, I'd say the 12v mode heater might get shut off at around 12.0v (roughly 50% charge on a lead-acid battery).

 

[NewmanRacing]

Thank you for your replies and guidance.

I am such an idiot! Teach me for working without my glasses on.

The problem started near the end of last season. Running the fridge on propane mode, with battery "fully" charged", the fridge would shut down with a dc LO code in about 2 hours. At that point the group 31 AGM battery was only 1.5 years old. I thought it could be either the vintage converter not charging the battery well, the propane safety on / off solenoid having a high current draw, or just a bum battery. I stored my wheel house for the winter.

While it was stored, I took the AGM to my supplier for testing. They stated the battery is still good with a voltage of 12.5. Not like new but not bad enough for them to replace it under warranty.

I pulled my rig out of storage and installed a Progressive Dynamics 4600 retrofit converter. I also eliminated the propane on/off solenoid to reduce battery consumption. Tested the gas system and let the converter run overnight to charge the battery.

I unplugged the converter and let the battery sit for a day to stabilize for testing. The following day I turn on the fridge and the trouble code flashed. I did not have my spectates on and I thought I saw dc LO. I also thought I left the gas on. It must have been No Flo.

The fridge has now run on propane overnight. All is well.

 

[Gary RV_Wizard]

While it was stored, I took the AGM to my supplier for testing. They stated the battery is still good with a voltage of 12.5. Not like new but not bad enough for them to replace it under warranty.

Sounds to me like they just wanted to avoid a warranty replacement.  Wonder if they load-tested it, vs just measuring volts at rest?  A lot of battery retail outlets don't really have much battery tech knowledge and a store clerk probably thinks a reading of 12.5 out of 12.6 possible is pretty darn good. Like getting a 9.9 at the Olympics...  :

 

[NewmanRacing]

I questioned him on the test, and asked the boss to repeat testing. They test for voltage and CCA. Testing CCA for an AGM deep cycle? Hmmm

I still have 6 more months on the warranty.

Norcold did respond. FYI Low cutout is about 10.5 volts.

 

[Gary RV_Wizard]

They cannot actually test CCA except in a lab.  To start with, CCA testing is done at 0 degrees F.!  What they can do is called a load test, which will give a reading somewhat analogous to CCA.  If they have good test equipment and a trained operator, the load tester can be set to mimic a demand similar to a cold starting load and yield a comparison to the CCA rating. Most stores and clerks don't do that calibration, though, and test using some arbitrary load value that is the same for all their testing, regardless of battery size or type. That's less accurate, of course.


Yes, deep cycle batteries usually have a CCA or MCA rating, though it will typically be lower than a "cranking battery" of the same physical size.  It may not be shown on the battery case, though. 

FYI Low cutout is about 10.5 volts.

Thanks, that's what I said in my earlier reply. Apparently it has only one low cut-off value, with no "smart" cut-off when using DC heater mode.