Write commands are accepted but the battery ignores them. Why?

External battery control must be explicitly enabled in the inverter's installer menu and set to 'External via protocol (Modbus TCP)'. If the mode is set to internal or digital I/O, the inverter will silently discard Modbus setpoints. Confirm the mode with the installer access credentials and retry.

The inverter reverts to internal control after a short time. What causes this?

The Plenticore Hybrid uses a watchdog timer: if the setpoint registers are not written cyclically within the configured timeout period, the inverter falls back to its own battery management. Ensure the ModbusCloud Gateway is sending writes to at least one of these registers before the timeout elapses.

Register values read back as nonsensical large numbers. What is wrong?

The Plenticore Hybrid defaults to Little-Endian (CDAB) byte order. External clients expecting Big-Endian float32 will decode garbage values. Set byte order to Big-Endian (ABCD) in the inverter's Modbus or SunSpec settings, then re-read the registers to confirm plausible values.

Is it safe to write any watt value to the charge and discharge setpoint registers?

Use caution. Writing values that exceed the battery's or inverter's rated power limits can trigger protection faults or may affect warranty conditions. The setpoints are not stored persistently: they are discarded on inverter restart. Always test with conservative values first and verify behavior before deploying automated control logic.

Free Modbus template: Kostal Plenticore Hybrid, incl. grid charging of the house battery (battery)

The Kostal Plenticore Hybrid is a three-phase hybrid PV inverter with integrated battery management, designed for residential and small-commercial solar-plus-storage installations. This template targets the external battery control interface over Modbus TCP, exposing two write-only setpoint registers: batterymode_a (address 1034) sets the absolute DC battery charge power, and batterymode_b (address 1040) sets the maximum discharge power limit. Together they allow an energy management system to command grid charging of the house battery and to cap discharge, without relying on the inverter's internal control logic. The ModbusCloud Gateway sends these setpoints cyclically before the inverter's watchdog timeout expires.

Name	Address	Function	Type	Unit	Access
batterymode_a Battery charge power (DC) setpoint, absolute value in watts.	1034	FC16	float32	W	W
batterymode_b Battery maximum discharge power limit, absolute value in watts.	1040	FC16	float32	W	W