Modbus TCP
OpenEMS Modbus-API (battery)
OpenEMS
Overview
OpenEMS Modbus-API is the built-in Modbus TCP slave interface of OpenEMS Edge, an open-source energy management system used in residential and commercial battery storage installations. The Modbus-API Controller generates a dynamic register map that exposes internal OpenEMS channels to external systems over TCP port 502. This battery template reads two key values from the _sum component: state of charge (register 302, mapped to _sum/EssSoc) and battery active power (register 415). Connect the ModbusCloud Gateway to the same network as the OpenEMS Edge host and import this template to track battery behavior without additional configuration.
Use cases
- Monitor battery state of charge continuously to detect abnormal self-discharge between charge cycles.
- Track active power at register 415 to verify the battery is charging or discharging as scheduled.
- Alert on state of charge dropping below a threshold during overnight discharge to protect battery longevity.
- Compare power values across multiple OpenEMS Edge sites from one ModbusCloud multi-site dashboard.
- Verify that battery power returns to zero after a scheduled charge window ends, confirming controller behaviour.
