Issue with "Soc" of ESS - InfluxDB

Hello,
I am facing an issue with my simulation. I am currently simulating a PV installation with batteries connected to the grid. I decided to display the grid consumption, PV production, site load, and battery power. The power values from each of these sensors seem correct. I only used the “Controller ESS Balancing” (target grid setpoint = 0) with “Simulator EssSymetric Reacting” with an initial 50% Soc.

However, I would also like to monitor the state of charge (SoC) of my battery. I selected the “ess0/Soc” option in InfluxDB. But as you can see, the SoC of my battery remains constant and never changes, even though the battery power varies (red graph).
Then, after quite a long time, it starts to go down but very slowly but never goes up.

Could you please provide some guidance on this issue?
Thank you very much in advance!

David