Modbus TCP times out and no registers are readable. What should I check?

Confirm that Modbus TCP is explicitly enabled in the KEBA eMobility app under Modbus settings; the interface is disabled by default. Also verify that no other system (OCPP backend, energy manager, or app) is holding an open connection, as the P40 supports only one Modbus TCP client at a time. Ensure the unit ID is set to 255 and the port is 502.

The power_factor value looks wrong. How is it scaled?

The power factor register returns cos phi in units of 0.1 percent. Divide the raw integer by 1000 to get a standard 0.0 to 1.0 value. For example, a raw reading of 998 means a power factor of 0.998. This scaling follows the same convention as the Keba P30 Modbus specification.

Phase switching is not triggering via set_trigger_phase_switch. Why?

Phase switching via Modbus requires firmware version 1.3.0 or later on the Keba P40. In addition, the phase-switching feature must be enabled under Photovoltaic Optimized Charging settings in the app, and set_phase_switch_source must be configured to assign control to Modbus before set_trigger_phase_switch will be accepted.

Is it safe to write to set_charging_current or set_enable at any time?

Use write registers with care. Writing 0 to set_enable terminates an active session immediately, which may surprise the vehicle driver and disrupt RFID-based authorization workflows. Setting set_charging_current below the vehicle minimum (typically 6 A) can cause the vehicle to stop charging without an explicit session end. Always confirm the failsafe_current_setting so the wallbox falls back to a safe current if Modbus communication is interrupted.

Free Modbus template: Keba P40

The Keba P40 is an AC EV wallbox designed for home, fleet, and semi-public charging at up to 22 kW. This Modbus TCP template reads active power, cumulative session energy, power factor, maximum and hardware-rated current limits, error codes, and phase-switch state. Write registers let your energy management system set the charging current, toggle charging on or off, trigger single-to-three-phase switching, and define session energy limits. Connecting the Keba P40 to the ModbusCloud Gateway gives installers live charging data, remote control, and failsafe-timeout visibility in one portal.

Name	Address	Function	Type	Unit	Access
error_code Active fault code; zero means no error present.	1006	FC03	uint32		R
serial_number Unique factory serial number of the wallbox.	1014	FC03	uint32		R
firmware Installed firmware version, encoded as a decimal integer.	1018	FC03	uint32		R
active_power Instantaneous AC charging power in watts.	1020	FC03	uint32	W	R
active_production_energy Cumulative energy delivered to connected vehicles, in watt-hours.	1036	FC03	uint32	Wh	R
power_factor Power factor (cos phi), scaled in 0.1 percent units.	1046	FC03	uint32	%	R
max_charging_current Currently configured maximum charging current in amperes.	1100	FC03	uint32	A	R
max_supported_current Hardware-rated maximum current the wallbox can supply, in amperes.	1110	FC03	uint32	A	R
energy_session Energy delivered in the current or most recent charging session.	1502	FC03	uint32	Wh	R
phase_switch_source Source controlling phase switching: local, Modbus, or external.	1550	FC03	uint32		R
phase_switch_state Current phase-switching state: single-phase or three-phase.	1552	FC03	uint32		R
failsafe_current_setting Charging current applied when Modbus communication is lost.	1600	FC03	uint32	A	R
failsafe_timeout_setting Timeout in seconds before failsafe current takes effect.	1602	FC03	uint32	s	R
set_charging_current Setpoint for maximum charging current, in amperes.	5004	FC16	uint16	A	W
set_energy_limit Setpoint for session energy limit; charging stops when reached.	5010	FC16	uint16	Wh	W
set_unlock_plug Command to unlock the charging plug from the vehicle.	5012	FC16	uint16		W
set_enable Enables or disables charging: write 1 to enable, 0 to disable.	5014	FC16	uint16		W
set_phase_switch_source Selects which source controls phase switching for this wallbox.	5050	FC16	uint16		W
set_trigger_phase_switch Triggers a phase switch between single-phase and three-phase mode.	5052	FC16	uint16		W

Keba P40

Overview

Use cases

Installation

Things to watch for

Registers (19)

Working with Modbus in your projects?

Free: RS485 and Modbus RTU installation checklist (PDF)

More Keba templates

Keba Modbus

KEBA Heat Distribution

More TCP templates

Algodue Energy meter UEM80-2D E

Sigenergy SigenStore EC (grid)

Fronius GEN24

HUAWEI SUN2000 Inverter & LUNA2000 battery

NIBE Nibe S-Series (SG Ready)

Fronius - Modbus TCP