Flickering lights when fridge runs?

I have a 12v system for the house load. The boat came with a fridge (110v). Year is unknown. I also purchased a chest freezer about 2 years ago.
Recently I replaced my inverter/charger with a True Sine inverter/charger, which is designed for marine setup.
Everything works fine, both 110/12v loads, except when the fridge runs (either the old fridge, or the new freezer, or both) the 110v lights are flickering. First I thought it was the fridge light, which is exactly 25W, conventional bulb. The inverter threshold is at 25W. I tried to change this limit on the inverter, but did not help.
However, the engine room lights are flickering, too. These are LED lights on 110v.
I did the troubleshooting with the manufacturer of the inverter. We tried different settings, plus at the end, they sent me a new inverter/charger to replace the first one. Same story. It flickers.
Just this weekend, I replaced all the wires in/out to the inverter with larger ones and with an oversized bus bar. The problem still exits. The manufacturer blames the fridge being old, since their tests on fridges did not result any flickering. The only problem with that is my fairy new freezer results the same issue, even when it runs by itself. For some reason, the fridge’s compressor run does not work well with my inverter.
I have 4 brand new LIFePO batteries, with plenty of capacity.

Anyone observed similar issues? Any thoughts about the solution to this? Thanks.

Most likely it is a modified sine wave or even sq. wave output on the inverter. easy to confirm. just plug into shore power see if the flickering goes away.

The easiest solution here is to look at the AC voltage and waveform both when the fridge is and is not running. It does require a scope though which most don't have and many technicians, even marine electricians won't have one. But on the off chance you know someone that has any kind of scope, you'll be able to find out what is going on right away, most else is just guessing in the dark.

Since it is doing it with both the newer freezer and the older fridge, I don't see any way to place the blame on either so you are down to wiring (which you just updated) or the inverter itself which you've also replaced. I would start by verifying all of the AC wiring going from the inverter to the circuits powering the fridge/freezer and make sure there are no loose connections or corrosion. AC Circuits are usually daisy chained so opening each outlet on a circuit and physically checking them is necessary to find bad connections.

This is an interesting problem. I really need more data. Did you replace an inverter or did you just add one. Do we know for a fact that we don't currently have a reverse polarity issue? I am under the impression that the problem showed up after the inverter was added and no other changes were made or were multiple electrical changes made at once?

Ka_sea_ta said:

Most likely it is a modified sine wave or even sq. wave output on the inverter. easy to confirm. just plug into shore power see if the flickering goes away.

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Yes, it does not happen on shore power. Only from battery inverted to 110v.

sbman said:

The easiest solution here is to look at the AC voltage and waveform both when the fridge is and is not running. It does require a scope though which most don't have and many technicians, even marine electricians won't have one. But on the off chance you know someone that has any kind of scope, you'll be able to find out what is going on right away, most else is just guessing in the dark.

Since it is doing it with both the newer freezer and the older fridge, I don't see any way to place the blame on either so you are down to wiring (which you just updated) or the inverter itself which you've also replaced. I would start by verifying all of the AC wiring going from the inverter to the circuits powering the fridge/freezer and make sure there are no loose connections or corrosion. AC Circuits are usually daisy chained so opening each outlet on a circuit and physically checking them is necessary to find bad connections.

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The previous inverter/charger (modified sine wave/Magnum) did not have this issue. There was no flickering.
This inverter is True Sine Wave inverter/charger (not Pure Sine).
The switch board, where AC goes into has been in place for years and no changes were made there, except some wire connections at each sub panel had to be upgraded to 50A capable wire, plus 50A breakers for the top of each sub panel. Nothing else. All connections looked clean and strong. I have eliminated the old wires from the switch panel to the bus bar and replaced the bus bar for the AC wire connections.
I think you are correct pointing out that the Sine Wave has something to do with this. I will try to get someone with a scope. Although, everything is working fine and it is not a big problem. It is just annoying to see the flickering.
Again, before the new inverter, there was no flickering, even with the old wires.

You just confused the issue. If it is not a Pure Sine Wave then it is a simulated sine wave. What model Magnum are you using. I would like to read the specifications on it.

Whose inverter , Mfgr, and model, are you using now? Not all so called Sine Wave inverters are the same.

tiltrider1 said:

You just confused the issue. If it is not a Pure Sine Wave then it is a simulated sine wave. What model Magnum are you using. I would like to read the specifications on it.

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I am not using Magnum now.
What have I confused?

C lectric said:

Whose inverter , Mfgr, and model, are you using now? Not all so called Sine Wave inverters are the same.

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I did not want to post the manufacturer, but since you asked, here is the model I am using, and it is brand new:

FREEDOM XC PRO Marine

I just saw on the manufacturer web site that there is a firmware upgrade available.
I will apply this tomorrow and see, if it fixes the problem.

By the way, I have observed something new this evening.
I left the shore power off since morning, so the house load was running from the inverter. Everything is fine and the batteries (LIFePO) were down to 13.2v.
Just when I walked in, the freezer came on. The fridge was off. I checked the fridge light and it was flickering. I went down to the ER and turned on the LED lights. There are 4 of them and 100W type. For a second the ER lights were flickering, but suddenly stabilized and stopped the flickering. I returned to the fridge and the light inside was steady. Also no flickering.
I turned up the fridge, too, just to see any changes, but no, the lights are steady now. Kind of strange.
The inverter’s display shows amp and voltage jumping up and down, when the flickering occurs. When the flickering stops, the voltage and amp is pretty steady.

I still suspect this has something to do with the inverter. Is it possible that the inverter’s load sensing is screwed up?
Let’s see what the firmware will result? I’ll report back.

Here you can see the inverter/charger is fueling the batteries at around 150 amps, as it suppose to. The shore power was turned on after the flickering test. The 4 LIFePO batteries are catching up fast.

LeoKa said:

Here you can see the inverter/charger is fueling the batteries at around 150 amps, as it suppose to. The shore power was turned on after the flickering test. The 4 LIFePO batteries are catching up fast.

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It's too bad scopes aren't more common and accessible. Can you try turning off any power saving/load sensing features and just have it in on/off mode that is manually controllable? If the flickering doesn't happen then, you'll know it's something related to the inverter's power save features.

sbman said:

It's too bad scopes aren't more common and accessible. Can you try turning off any power saving/load sensing features and just have it in on/off mode that is manually controllable? If the flickering doesn't happen then, you'll know it's something related to the inverter's power save features.

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I did try that already.
I have not shared this, but prior this entry, I have had 2-3 weeks troubleshooting with the manufacturer. They have suggested different settings and one of them was your suggestion. It did not make any difference.
Since there was another issue with the first unit I had, (overcharging the batteries, which resulted safety shut off the charge at 14.8 volts, alarm on, back to charge again, over and over), they sent me a new unit. The overcharge is gone, but this load sensing issue is still with me.
Again, it does not cause any serious problems, it just bugs me.

No were in their literature do they define what true sine wave means. They do advertise pure sine wave units and they say that right on the unit “pure sine wave”. I am suspicious of what the definition of true sine wave means. I also noticed it only says “sine wave” on the box. I personally do not trust xantrex, they are always the cheapest product at a given specifications but I have always had reliability issues with xantrex labeled equipment.

The problem doesn’t occur on shore power. Didn’t occur with the old inverter and the only change was the inverter. At this point you either need to scope it as recommended above or try a different inverter.

LeoKa said:

I did try that already.
I have not shared this, but prior this entry, I have had 2-3 weeks troubleshooting with the manufacturer. They have suggested different settings and one of them was your suggestion. It did not make any difference.
Since there was another issue with the first unit I had, (overcharging the batteries, which resulted safety shut off the charge at 14.8 volts, alarm on, back to charge again, over and over), they sent me a new unit. The overcharge is gone, but this load sensing issue is still with me.
Again, it does not cause any serious problems, it just bugs me.

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I would not be happy with that. It may not cause a problem now, but what about when you want to charge a laptop or other sensitive equipment, will it behave then? How long will it take to damage something? How long will your LED lights last with the varying power levels? If the manufacturer can't fix the issue, I'd be looking to return and get a different inverter that doesn't have that issue.

Flickering Lights...

Reminded of the Lucas 3 position switch : Off/ Dim/ Flicker

tiltrider1 said:

No were in their literature do they define what true sine wave means. They do advertise pure sine wave units and they say that right on the unit “pure sine wave”. I am suspicious of what the definition of true sine wave means. I also noticed it only says “sine wave” on the box. I personally do not trust xantrex, they are always the cheapest product at a given specifications but I have always had reliability issues with xantrex labeled equipment.

The problem doesn’t occur on shore power. Didn’t occur with the old inverter and the only change was the inverter. At this point you either need to scope it as recommended above or try a different inverter.

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I would have to agree on the TRUE SINE WAVE point. What is the difference?

Generally speaking! It maybe trying to output a real sine wave and as the load increases. The wave becomes more of a square wave.

My guess would still be you are having an issue with load sensing, i.e. the inverter probes the wires to see if it needs to turn on. Simple test. Try adding a large constant resistance load (not LED or inductive) of about 200-300W and see if you still have flickering.

My beer and bait 110V fridge does the same thing when run on my modified sine wave inverter but not on shore power. It doesn't affect the function of the fridge and after 4 years of use, I hardly notice it any longer.

gsholz said:

My guess would still be you are having an issue with load sensing, i.e. the inverter probes the wires to see if it needs to turn on. Simple test. Try adding a large constant resistance load (not LED or inductive) of about 200-300W and see if you still have flickering.

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Agree. If you add a lamp with a old fashioned 60w filament bulb as a load the flickering may stop. It’s not acceptable behavior.

Here's an inexpensive Oscope if you decide to go that way. It's on Amazon.
YEAPOOK ADS5012h Handheld Digital Portable Oscilloscope Mini Storage Oscilloscope Kit with 100MHz Bandwidth 500MS/s Sampling Rate 2.4'' TFT LCD Display.
https://smile.amazon.com/YEAPOOK-Ha...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

While the lights are flickering try adding an additional load to the inverter. Some manufactures have a standby mode and while enabled will look for a load then actually provide power. The light might be below the amp setting and not enough for the inverter to sense, sounds strange but believe me its frustrating.
Whats even more frustrating is finding all the settings that will allow the change to be enabled. I service 12 rental boats and have begun using xantrex equipment this is where I have been experiencing the problem.

https://youtu.be/tIK_elxgOEs
Might want to take a look at this and see if it might help, sorry did not paste as a link.
Good Luck!!

SBR said:

While the lights are flickering try adding an additional load to the inverter. Some manufactures have a standby

Good Luck!!

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I watched the video and I think you are correct that the load sensing is malfunctioning on mine.
I did change this settings to off, (also the standby mode) as it was recommended by the manufacturer, but it did not make any difference. I tried to find another light bulb for the fridge with different wattage, but I could not. The socket is very particular.
It is also true, if I add another load, while the fridge is running; everything starts to work properly. No flickering, no voltage/amp numbers scatter all over on the display.
What is interesting about this, when the fridge runs by itself from inverter, it flickers. When I run my chest freezer together with the fridge; it still flickers. If I add another load, like a fan, or dehumidifier; the voltage is stabile and no flickering. This is true either with the fridge or the freezer individually, or together.
Something inside the inverter’s circuit is not happy with the fridge/freezer compressor/motor.

Leatherneck said:

Here's an inexpensive Oscope if you decide to go that way.

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I did order a scope, basic but capable, and I would not mind to use it. Any advice where to start the troubleshooting?

I would disconnect from shore power and plug into one of the ac outlets serviced by your inverter, then look at the waveform to see if it is a sine wave or square wave. See if it changes when you add loads.

With the chest freezer on and still light flickers are you sure the freezer was actually running, in other words actually cooling? Just a thought. Maybe try plugging a lamp or some thing in at the freezer outlet and see what happens?

Yes, it was/is running. First, it has an LED, which shows that is powered on. Second, I can hear it, when it is running and cooling.

Well then I would agree with Leatherneck as a good starting point, please be sure to post what you find I am very interested in hearing the results.

Leatherneck said:

I would disconnect from shore power and plug into one of the ac outlets serviced by your inverter, then look at the waveform to see if it is a sine wave or square wave. See if it changes when you add loads.

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Will do. I’ll report back, when the scope arrives.