Greetings to everyone. I am having problems with a Voltronic Axpert 8Kw inverter, which measures a different battery voltage than the BMS. I performed the calibration procedure and it seemed to work, but as soon as it started discharging, the difference returned to -0.3V and sometimes even reaches -0.5V, meaning the inverter measures lower values than the BMS. Does anyone know how I can resolve this? Thank you so much to anyone who can help me.

Edited February 22, 20251 yr by enzomcn

On the same note above, am also having similar difference in information received by inverter via pmbsTools (which is more accurate) than my inverter. My battery SoH on the inverter is 100%, yet info via pmbsTools is now at 98%. Could this be a comms cable issue or inverter "rounds-off" info it receives from battery?

16 hours ago, enzomcn said:

Greetings to everyone. I am having problems with a Voltronic Axpert 8Kw inverter, which measures a different battery voltage than the BMS. I performed the calibration procedure and it seemed to work, but as soon as it started discharging, the difference returned to -0.3V and sometimes even reaches -0.5V, meaning the inverter measures lower values than the BMS. Does anyone know how I can resolve this? Thank you so much to anyone who can help me.

Your computers ink level is low 

2 hours ago, Moffat said:

On the same note above, am also having similar difference in information received by inverter via pmbsTools (which is more accurate) than my inverter. My battery SoH on the inverter is 100%, yet info via pmbsTools is now at 98%. Could this be a comms cable issue or inverter "rounds-off" info it receives from battery?

unfortunately it's not a cable problem, because if I measure with the tester directly on the battery connections with the tester there is always a difference

36 minutes ago, Demo said:

Your computers ink level is low 

😁

1 hour ago, enzomcn said:

unfortunately it's not a cable problem, because if I measure with the tester directly on the battery connections with the tester there is always a difference

Point taken, the only disappointing part is that this battery was installed one day before Christmas in 2024 and already am at 98% SoH (February 20, 2025), will keep documenting it's level of degradation.

22 hours ago, enzomcn said:

having problems with a Voltronic Axpert 8Kw inverter, which measures a different battery voltage than the BMS

A Voltronic expert might know if they have offset values that can be set. I would think they do, but it is normally a hidden menu item.
I had the exact same issue with my Growatts. Luckily they have a menu item which then opens a sub menu list with offsets for every conceivable value, some of the abbreviations I don't even have a clue what they are for, some are quite obvious.
Suffice to say, I was able to offset both Inverters individually to ensure the same readings as the Battery.

 

Edited February 22, 20251 yr by zsde

I still have the old fashioned view that inverters are not calibrated instruments and the "error" of less than 1% would not bother me. 

1 hour ago, Scorp007 said:

I still have the old fashioned view that inverters are not calibrated instruments and the "error" of less than 1% would not bother me. 

the problem is that when it is discharging it can reach a difference of 700mV and therefore the inverter switches to the mains when the battery is still charged

1 hour ago, enzomcn said:

the problem is that when it is discharging it can reach a difference of 700mV and therefore the inverter switches to the mains when the battery is still charged

Have you tried just using a lower setting to compensate for the "error" 

39 minutes ago, Scorp007 said:

Have you tried just using a lower setting to compensate for the "error" 

I did the calibration. It seems to work, but the next day the error returned.

On 2025/02/23 at 5:35 AM, enzomcn said:

the problem is that when it is discharging it can reach a difference of 700mV and therefore the inverter switches to the mains when the battery is still charged

Ah. That's a lack of load compensation for the battery voltage measurement. Sadly, unpatched firmware has no code for this, and patched firmware for this issue is not available for any modern model.

On 2025/02/23 at 7:18 AM, enzomcn said:

I did the calibration. It seems to work, but the next day the error returned.

Did you use a PSAVE command to save the calibration value? Otherwise, the value is soon lost. You could use monitoring software to make any battery related settings change, then put it back again. Each of these commands saves all the settings and calibration data each time, as far as I know.

On 2025/02/21 at 10:44 PM, enzomcn said:

Greetings to everyone. I am having problems with a Voltronic Axpert 8Kw inverter, which measures a different battery voltage than the BMS. I performed the calibration procedure and it seemed to work, but as soon as it started discharging, the difference returned to -0.3V and sometimes even reaches -0.5V, meaning the inverter measures lower values than the BMS. Does anyone know how I can resolve this? Thank you so much to anyone who can help me.

Thanks for raising this issue, I also planing to calibrate the battery voltage as the reading on the inverter is -0.3V less from the BMS and I do really appreciate if there is a document with the correct order of commands for my inverter.

I have Axpert VM3 4K Twin with FW 60.10 and 25.15.

On 2025/02/26 at 5:27 AM, AMalakani said:

if there is a document with the correct order of commands for my inverter.

The calibration commands are all the same for all Axperts, apart from the smallest ones.

On 25/02/2025 at 13:48, Coulomb said:

Hai usato un comando PSAVE per salvare il valore di calibrazione? Altrimenti, il valore andrà perso presto. Potresti usare un software di monitoraggio per apportare modifiche alle impostazioni relative alla batteria, quindi ripristinarle. Ognuno di questi comandi salva tutte le impostazioni e i dati di calibrazione ogni volta, per quanto ne so.

unfortunately the only command that I didn't give is "PSAVE". maybe that's why it doesn't work. tomorrow I'll try and keep you updated. thank you very much