All registers read zero even though the wallbox is powered.

Confirm Modbus TCP is explicitly enabled in the wallbox communication settings. The factory default may have Modbus disabled. Also verify unit ID is set to 255, which is the standard unit identifier for this device family. A mismatch will return no data.

The gateway connects but string registers show garbled characters.

String registers such as serial_number and firmware_version are encoded as multi-register ASCII blocks. Ensure the template is reading the correct number of consecutive registers for each string field and that your client is assembling them in big-endian byte order, as used by this device.

The wallbox drops to its failsafe current after a few minutes.

The Webasto Unite requires the Modbus master to periodically write to the alive_register_b (address 6000) to signal the connection is still live. If that keepalive write stops, the device falls back to the failsafe_current value after the failsafe_timeout expires. Ensure the ModbusCloud Gateway is writing the alive register at least once within the configured timeout interval.

Is it safe to write any value to charging_current_b at any time?

No. Writing a charging current value outside the range bounded by evse_min_current and evse_max_current can cause the session to abort or the EVSE protection to trip. Always read the current limits first and clamp your setpoint within them. Uncontrolled writes may also affect warranty coverage, so test changes carefully in a controlled environment.

Free Modbus template: Webasto Unite

Name: Webasto Unite
Brand: Webasto
SKU: fe2e330b-2d55-43e3-8cfe-056a673a404b

The Webasto Unite is an AC EV wallbox delivering up to 22 kW over one or three phases, designed for residential, fleet, and commercial charging installations. This ModbusCloud template connects via Modbus TCP and reads charge point state, cable state, per-phase current and voltage, active power on all three phases, session energy, and session timestamps. Write registers let your energy management system set the charging current and keepalive in real time. The template gives installers and facility managers live visibility and dynamic load control without additional hardware.

Registers (41)

37 read / 4 write

Name	Address	Function	Type	Unit	Access
serial_number Unique serial number string of the wallbox unit.	100	FC04	string		R
charge_point_id Configured identifier string for this charge point.	130	FC04	string		R
brand Manufacturer brand name string reported by the device.	190	FC04	string		R
model Model name string reported by the device firmware.	210	FC04	string		R
firmware_version Installed firmware version string of the wallbox.	230	FC04	string		R
date Current date value from the wallbox internal clock.	290	FC04	uint32		R
time Current time value from the wallbox internal clock.	294	FC04	uint32		R
charge_point_power Rated maximum power capacity of the charge point, watts.	400	FC04	uint32	W	R
number_of_phases Number of AC phases currently active for charging.	404	FC04	uint16	count	R
charge_point_state Overall state of the charge point, encoded as uint16.	1000	FC04	uint16		R
charging_state Active charging session state, encoded as uint16.	1001	FC04	uint16		R
equipment_state EVSE equipment operational state, encoded as uint16.	1002	FC04	uint16		R
cable_state IEC 61851 cable/connector state, encoded as uint16.	1004	FC04	uint16		R
evse_fault_code Active EVSE fault code; zero indicates no fault.	1006	FC04	uint32		R
current_l1 Instantaneous charging current on phase L1, amperes.	1008	FC04	uint16	A	R
current_l2 Instantaneous charging current on phase L2, amperes.	1010	FC04	uint16	A	R
current_l3 Instantaneous charging current on phase L3, amperes.	1012	FC04	uint16	A	R
voltage_l1 AC voltage on phase L1, volts.	1014	FC04	uint16	V	R
voltage_l2 AC voltage on phase L2, volts.	1016	FC04	uint16	V	R
voltage_l3 AC voltage on phase L3, volts.	1018	FC04	uint16	V	R
active_power Total active charging power across all phases, watts.	1020	FC04	uint32	W	R
active_power_l1 Active charging power on phase L1, watts.	1024	FC04	uint32	W	R
active_power_l2 Active charging power on phase L2, watts.	1028	FC04	uint32	W	R
active_power_l3 Active charging power on phase L3, watts.	1032	FC04	uint32	W	R
meter_reading Cumulative energy meter reading from the wallbox.	1036	FC04	uint32	kWh	R
session_max_current Maximum current limit applied in the current session, amperes.	1100	FC04	uint16	A	R
evse_min_current Minimum current the EVSE can deliver, amperes.	1102	FC04	uint16	A	R
evse_max_current Maximum current the EVSE hardware supports, amperes.	1104	FC04	uint16	A	R
cable_max_current Maximum current rating reported by the connected cable.	1106	FC04	uint16	A	R
energy_session Energy delivered during the current or last session.	1502	FC04	uint32	kWh	R
session_start_time Timestamp when the current charging session started.	1504	FC04	uint32		R
session_duration Elapsed duration of the current charging session.	1508	FC04	uint32	s	R
session_end_time Timestamp when the last charging session ended.	1512	FC04	uint32		R
failsafe_current_a Configured failsafe current fallback value, amperes (read).	2000	FC03	uint16	A	R
failsafe_timeout_a Configured failsafe timeout value in seconds (read).	2002	FC03	uint16	s	R
charging_current_a Active charging current setpoint currently applied, amperes (read).	5004	FC03	uint16	A	R
alive_register_a Keepalive register value; must be toggled periodically (read).	6000	FC03	uint16		R
failsafe_current_b Failsafe current setpoint written by the Modbus master, amperes.	2000	FC16	int16	A	W
failsafe_timeout_b Failsafe timeout setpoint in seconds written by the master.	2002	FC16	int16	s	W
charging_current_b Charging current command written by the Modbus master, amperes.	5004	FC16	int16	A	W
alive_register_b Keepalive write register; master must update to prevent failsafe.	6000	FC16	int16		W