Modbus register for Pylontech min/max cell voltage

Hello,
I’m already using Modbus/TCP to read/set various values of our GX device.
Currently I’m looking to read the min/max cell voltages from our Pylontech batteries, as they are causing more and more issues with balancing. Is there a way to get these values as they are shown in the remote console?
grafik

I’ve been searching in the current CCGX-Modbus-TCP-register-list-3.40.xlsx, but couldn’t find anything that works.

Thanks upfront!

Registers 1290 and 1291…
Only that their resolution is 2 decimals (3.45) and you may need 3 decimals (3.456).
But this is doable, by modifying a file on the Venus OS.

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Thanks very much, I had tried 1290 and 1291 before, but somehow failed while setting up the polling timer, it returned null values…
Now I got it working, unit id had also to be set to 225 (CAN-bus BMS) of course :slight_smile:

This helped me out too, thank you Alex.

Would you be able to point me in the right direction for the file modification to get a precision of 3 on the Highest/Lowest Cell Voltage registers?

Thank you :slight_smile:

Inside Venus OS, that you’ll be accessing through SSH, you will find the modbus driver inside the /opt/victronenergy/dbus-modbustcp folder.

Inside that folder you’ll find a file named attributes.csv.
Edit that file and find the following lines:

com.victronenergy.battery,/System/MinCellVoltage,d,V DC,1290,uint16,100,R
com.victronenergy.battery,/System/MaxCellVoltage,d,V DC,1291,uint16,100,R

Towards the end of the lines, there are two 100 values. Those are precision, i.e. how many digits after decimal point.
Modify them as 1000 instead of 100.

Then restart the modbus service, by going into Cerbo’s Settings → Services → Modbus TCP → Enable / Disable.

That’s all. Now instead of something like 325, you’ll get something like 3253, for a 3.253 value.

PS: See that inside VRM, even if you are sending with 3 digits, still only 2 are used and displayed.

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