Hello,

There is the following setup:

3 x EASUN SV4 in parallel

same firmware 56.14 and

same panels config for all( 7 in series for each). 350V ,

When panels of the third one are connected using DC breaker and the sun is shining , the charge current increase to 20A limit , after 4 to 10 minutes ,Error 72 appears and output of inverters is disable.

If panels of the third inverter are disconnected using the DC beaker, everything works fine, and there is No error.

I checked the wiring of parallel cables for communication and current and everything is OK. Each inverter is working fine into SIG mode.

Could be an interference issue? Indeed parallel cables are along with DC cables for 2 meters into the same cable bed. There in no shield for the cables.

Had anyone this kind of issue? Could be EASUN SV4 such sensible at interference?

Could be the above solution also for EASUN SV4?

Updates:

I checked all cables, replace paralel card from each, one by one with a new card, and tested different setups, all with parallel cables connected and untouched.

setup1: inv 1 and inv 2 started from button and inv 3 stopped from button with PV panels on, charging only the battery. Works OK.

setup2: inv 1 , inv 2, inv 3 started from button and with PV panels from inv3 off. Works OK.

setup3: inv 2 and inv 3 started from button and inv 1 stopped from button with PV panels on, charging only the battery. Works OK.

setup4: inv 1 , inv 2, inv 3 started from button and with PV panels from inv1 off. Works OK.

setup5: inv 1 and inv 3 started from button and inv 2 stopped from button with PV panels on, charging only the battery. Works OK.

setup6: inv 1 , inv 2, inv 3 started from button and with PV panels from inv2 off. Works OK.

I have changed battery charging curent to: 10A/10A/10A , 20A 20A 10A , 30A 30A 30A, 10A 20A 30A, no solution, error 72 comes after ~5 min.

I have measured the output voltage from inverters on different loads, but the values are near below ones:

inv1-Vout AC: 229.8V

inv2-Vout AC: 230.2V +1m wire longer than inv1

inv3-Vout AC: 229.4V +1m wire longer than inv1

There is no error when is not a sunny day , all works together fine.

Any idea what could be ? what to check further?

Can you check if inverter 3 is missing a capacitor across the PV inputs? MKS IVs are known to be sensitive to this, usually affecting the display, but it might conceivably trigger other issues.

There is a small file in the downloads section with slightly more detail. Be aware of the safety issues if you take this on yourself. Big high voltage capacitors can cause nasty shocks and/or damage underwear.

Edit: Since fault code 72 is to do with current sharing, it may be to do with the length and/or resistance of the AC-out cables. If these are significantly different (you mention a 1 metre difference), it could be worth lengthening the cables from inverter 1 to the joining point, so that the lengths are more even.

It's also possible that the current sense circuit for inverter 3 (or others) has a bad capacitor that would normally smooth out noise, for example from the PV input cables.

Edited April 7Apr 7 by Coulomb

On 2026/04/07 at 7:22 AM, Coulomb said:

the PV inputs

On 2026/04/07 at 7:22 AM, Coulomb said:

Can you check if inverter 3 is missing a capacitor across the PV inputs? MKS IVs are known to be sensitive to this, usually affecting the display, but it might conceivably trigger other issues.

There is a small file in the downloads section with slightly more detail. Be aware of the safety issues if you take this on yourself. Big high voltage capacitors can cause nasty shocks and/or damage underwear.

Edit: Since fault code 72 is to do with current sharing, it may be to do with the length and/or resistance of the AC-out cables. If these are significantly different (you mention a 1 metre difference), it could be worth lengthening the cables from inverter 1 to the joining point, so that the lengths are more even.

It's also possible that the current sense circuit for inverter 3 (or others) has a bad capacitor that would normally smooth out noise, for example from the PV input cables.

All the inverters have the capacitor installed from factory.

I equal all the Vout wires having the same length and size , but the same result , Error 72 after a certain time. Next check , I will replace each inverter, one by one with a new one to see if there is any improvement.

Any other ideas before what I said ?

I would check for earth leaks on the PV panels. Or generally any leaks between the panels if they are not earthed.

It's only one of many possibilities, but easy to verify.

9 hours ago, kuba.cz said:

I would check for earth leaks on the PV panels. Or generally any leaks between the panels if they are not earthed.

It's only one of many possibilities, but easy to verify.

The strings are connected to own earth into a different point than inverters. Works any combination of 3 inverters without error , if one of them(randomly) is closed from button or has PV string disconnected using DC switch breaker. I will check ,anyhow ,what you suggested, thanks! One remark: I saw there is a difference sometimes of 0.2V max between inverters as they see the battery.

Update:

I changed one inverter , the third one, was the inverter which didn't give error often and the problem is solved. I noticed also that one parallel curent cable wasn't tight enough, so I fixed that also. I remember that I checked it before, twice and was ok. So... , now... a good test should be to change back the old inverter and check, but this will not happen on short future... .Anyhow I will check the inverter on another setup to have a conclusion. Many thanks @kuba.cz and @Coulomb for your answers. 🙏

Updates: After ~ 45 days Error 72 is back, without any intervention/change/touch on the setup. Now is hard to understand this situation and find a solution. I have checked also the old inverter and works fine on bench. Any ideas?

On 2026/03/17 at 4:46 AM, ClMo said:

same firmware 56.14

If your inverters were made before May 2024, it might be worth trying factory firmware version 56.72. But note that there is no way to go back if it's worse, other than asking your supplier for the latest firmware update. [ Edit: 56.72 is a VM III firmware; if these inverters are paralleled, then they can't be running VM firmware. ]

On 2026/04/24 at 2:01 PM, ClMo said:

I saw there is a difference sometimes of 0.2V max between inverters as they see the battery.

That should not affect fault code 72, current sharing, as far as I know. And it's fairly close. But it might be worth calibrating the battery voltage measurements to rule it out.

Edited May 23May 23 by Coulomb

On 2026/05/21 at 6:58 AM, Coulomb said:

If your inverters were made before May 2024, it might be worth trying factory firmware version 56.72. But note that there is no way to go back if it's worse, other than asking your supplier for the latest firmware update.

That should not affect fault code 72, current sharing, as far as I know. And it's fairly close. But it might be worth calibrating the battery voltage measurements to rule it out.

Factory version was 56.13, and production date is 08.2024. I could give a try to flash back to factory version . After I replaced the third inverter , there is only 0.1V difference for battery during this time. I could try also a battery calibration but I am skeptical that will solve the issue. The latest firmware from supplier was 56.14.

Update: Observation - When is a load of ~5kw and entire energy is from PV , the Vout AC drops to 220V from 230V , and when PV is not suficient and the battery is discharging rise back to 230V. Is this a firmware bug?

10 hours ago, ClMo said:

When is a load of ~5kw and entire energy is from PV , the Vout AC drops to 220V from 230V , and when PV is not sufficient and the battery is discharging rise back to 230V. Is this a firmware bug?

That's a great observation.

When the entire load is coming from PV, the DC<->DC converter is running backwards from the DC bus via the buck converter into the battery. The DC bus voltage is set by the PV's boost converter, often not boosting at all (basically passing through the PV voltage less a diode drop).

When PV power is not sufficient, the DC<-> converter is running forwards, pushing battery power into the battery, with the buck converter passing through the transformed battery voltage less an IGBT drop. The DC bus voltage is basically set by the battery voltage and the transformer turns ratio.

So the problem would appear to be that the Solar Charge Controller is not setting the DC bus high enough to produce a 230 V sine wave. That could be partly because of the "PV stuck at 90 V" (perhaps 120 V for your model), coupled with a firmware bug that is not setting the DC bus voltage high enough. The Solar Charge Controller firmware is part of the main (DSP, U1) firmware in these models. Perhaps there is a hardware fault with one of the inverters, such that the DC bus voltage is not measured correctly.

I'm now confused about your firmware. 56.xx is one of those number ranges that several different models use. I have Infini, VM III, King 1 rack mounted, and Max II 10kW firmwares in my collection. Your model appears to be an Axpert MKS IV, but I don't have any MKS IV firmwares with 56.xx firmware. I can't be an MKS III model, since as far as I know, these don't even have provision for a paralleling board. My guess is that there is a whole range of MKS IV 56.xx firmwares that I have not collected, perhaps due to numbering collisions with firmwares I already had.

You mentioned going back to "as delivered" 56.13, and you updated to 56.14. Do you have these firmware update files? There might be an EEPROM layout issue with these firmwares that I can identify.

Edit: I now believe that you have an Infinisolar V IV rebranded as an Easun. I don't collect these firmwares any more, and have little knowledge of them. These are "on-grid" models in Voltronics' terminology, capable of exporting to the grid. The Infinisolar Vs have hardware similar in circuitry and in the case of Infinisolar V IVs, similar appearance to some Voltronic Axpert ("off-grid") models.

Edited May 24May 24 by Coulomb

5 hours ago, Coulomb said:

5 hours ago, Coulomb said:

That's a great observation.

When the entire load is coming from PV, the DC<->DC converter is running backwards from the DC bus via the buck converter into the battery. The DC bus voltage is set by the PV's boost converter, often not boosting at all (basically passing through the PV voltage less a diode drop).

When PV power is not sufficient, the DC<-> converter is running forwards, pushing battery power into the battery, with the buck converter passing through the transformed battery voltage less an IGBT drop. The DC bus voltage is basically set by the battery voltage and the transformer turns ratio.

So the problem would appear to be that the Solar Charge Controller is not setting the DC bus high enough to produce a 230 V sine wave. That could be partly because of the "PV stuck at 90 V" (perhaps 120 V for your model), coupled with a firmware bug that is not setting the DC bus voltage high enough. The Solar Charge Controller firmware is part of the main (DSP, U1) firmware in these models. Perhaps there is a hardware fault with one of the inverters, such that the DC bus voltage is not measured correctly.

I'm now confused about your firmware. 56.xx is one of those number ranges that several different models use. I have Infini, VM III, King 1 rack mounted, and Max II 10kW firmwares in my collection. Your model appears to be an Axpert MKS IV, but I don't have any MKS IV firmwares with 56.xx firmware. I can't be an MKS III model, since as far as I know, these don't even have provision for a paralleling board. My guess is that there is a whole range of MKS IV 56.xx firmwares that I have not collected, perhaps due to numbering collisions with firmwares I already had.

You mentioned going back to "as delivered" 56.13, and you updated to 56.14. Do you have these firmware update files? There might be an EEPROM layout issue with these firmwares that I can identify.

Edit: I now believe that you have an Infinisolar V IV rebranded as an Easun. I don't collect these firmwares any more, and have little knowledge of them. These are "on-grid" models in Voltronics' terminology, capable of exporting to the grid. The Infinisolar Vs have hardware similar in circuitry and in the case of Infinisolar V IVs, similar appearance to some Voltronic Axpert ("off-grid") models.

SV-IV-56.13.rar

Edited May 24May 24 by ClMo

Just now, ClMo said:

SV-IV-56.13.rar

SV-IV-56.14_last_from_easun_banban.rar

1 minute ago, ClMo said:

SV-IV-56.14_last_from_easun_banban.rar

The name into the file is " INFINI V IV 5.6K 56.14" , so they cloned " InfiniSolar V IV" but in reality only they know .

On 2026/05/24 at 10:16 AM, Coulomb said:

There might be an EEPROM layout issue with these firmwares that I can identify.

No, the two EEPROM layouts are identical. So that's not the issue. Intriguingly, the hex file for 56.13 is three days later than that for 56.14.

Both are definitely Infini firmwares, as confirmed by the folder names.

So sorry, I have no idea what the issue is. Interference is possible, but it seems unlikely to me.

Update: I started replacing all of my current sharing cables and in the process I identified the problem. One cable had a ferrule that wasn't thin enough and had poor contact there. I assume the ferrule was placed there to improve contact, but that ended up being the reason for the error 72. By crimping with a different ferrule the error goes away and hopefully forever. Thanks a lot! @Coulomb Enjoy your coffee!

Update: Yesterday was white strong light from the sun and the error came back after more than 20 days. This is nuts .