Modbus TCP
St-ems wattsonic (battery)
St-ems
Overview
The St-ems wattsonic is a hybrid solar inverter with integrated battery storage, sold under the Wattsonic brand and rebadged by St-ems. The ModbusCloud template connects over Modbus TCP and reads two key battery registers: instantaneous charge or discharge power (address 40258) and state of charge (address 43000). It also exposes a writable minimum-SOC setpoint (address 52503) that lets an energy management system reserve battery capacity. Importing this template into your ModbusCloud portal gives you live battery visibility and basic remote control without manual register configuration.
Use cases
- Monitor real-time battery charge and discharge power to verify the system follows the expected self-consumption pattern.
- Track state of charge over time to detect capacity degradation across heating seasons.
- Alert on SOC dropping below a threshold during grid outages to trigger manual load shedding.
- Report daily battery cycling data to building owners as part of a monthly energy performance summary.
- Verify that the limitsoc setpoint takes effect after writing, by comparing the register readback against the intended value.
