BMS error : what causes it?

aristoweb · February 15, 2025, 9:43am

Good morning everyone

What could cause BMS error in general?

I have an Aton ATZ-3K-AC inverter with firmware from 26-9-2024 connected to a photovoltaic panel system and a storage system of 4 Pylontech batteries of which 3 US2000 and 1 US2000C added a few days ago after about 1 and a half years.

The battery firmware is for all 4 Pylontech batteries version 2.8 from 22-09-2002.

The batteries seem to charge and discharge and the fourth US2000C battery is seen correctly by the Pylontech BatteryView software.

The problem is that on the Aton inverter screen I have the following error messages in sequence:

91 BMS ERROR
92 BMS WARNING
B01 ERR COMM
B02 ERR COMM
B03 ERR COMM

I also disconnected the entire system for 15 minutes and turned it back on but after a while the 5 error messages appear again.

What could it be in your opinion and how can I solve it?

Would updating the firmware of the Pylontech US2000C which is connected as master solve the problem?

Richard_Mackay · February 15, 2025, 3:02pm

Disconnect this battery so the system is as it was and see if there is still a fault…

mmaritz · February 15, 2025, 3:23pm

Don’t connect it as Master… Leave the old master…

TheTerribleTriplet · February 15, 2025, 3:30pm

Could also be that a BMS is switching off/disconnecting, due to a problem on the bank, a bank …

Check for any issue, volts per cell or bulging of a case.

aristoweb · February 15, 2025, 3:44pm

I tried disconnecting the last battery and the errors remain

aristoweb · February 15, 2025, 6:06pm

So I should to use batteryview for to check the cells?

aristoweb · February 15, 2025, 6:07pm

The old batteries are three US2000.

The new battery is a US2000C and Pylontech replied to me saying that it must be connected as Master.

TheTerribleTriplet · February 16, 2025, 8:19am

Yes.

Then you can eliminate that as a potential cause.

And it is good to monitor the cell volts over time to pre-empt potential problems.

aristoweb · February 16, 2025, 10:29am

The connection of my 4 batteries with my photovoltaic system and my inverter was done by a specialized technician.

The display of my Aton inverter shows error messages after a specialized technician added a Pylontec US2000C to my rack of 3 Pylontech US2000 batteries.

The error messages displayed on the inverter display are:

91 BMS ERROR
92 BMS WARNING
03 GRID VOLTAGE ERROR
71 FAULT
B01 ERR COMM
B02 ERR COMM
B03 ERR COMM

I have 4 Pylontech batteries including 3 US2000 and 1 US2000C.

Master - Pylontech US2000C
Slave 1 - Pylontech US2000
Slave 2 - Pylontech US2000
Slave 3 - Pylontech US2000

However, trusting only myself, I checked the connection diagram recommended by Pylontech and those made by my technician.

The communication connections between batteries and inverter are correct.

However, I found an error in the power connections between batteries and inverter.

In particular, the positive (+) of the master battery should be connected to the positive (+) of the inverter, right?

Instead the technician connected the positive (+) of the master battery to the positive (+) of the slave battery 1.

And currently the positive (+) of the slave battery 3 is connected to the positive (+) of the inverter.

Is this a real error?

Could this create the error messages on the display of my inverter?

The firmware on my Pylontech US2000C master battery is version 2.8.

Should I install a more updated version?

Does anyone know what the latest firmware version is for the US2000C?

Also all the ADD dip switches on all 4 batteries are down (OFF): is this correct?

aristoweb · February 16, 2025, 10:31am

Thank you for your answer I appreciate it a lot.