NexBlue Modbus Documentation

Applicable Location: SDU

Applicable models: Edge 2, Edge Max, and Point 2 (UK)

Applicable firmware version: 03.09.61 and above

1. Communication Channel

Channel type: TCP/IP
Physical interface: RJ45 Ethernet cable connection / Wi-Fi connection

2. TCP/IP Communication

2.1 Network Configuration

Network mode: DHCP dynamic IP acquisition
Fallback mode: Static IP configured in the app

In DHCP mode, after power-on, the device automatically requests an IP address from the DHCP server. After an address is successfully obtained, the device broadcasts its information via mDNS. The broadcast service name is:

_nexblue_modbus._tcp.local

This can be automatically discovered by EMS systems that support mDNS, such as Home Assistant and Tibber.

2.2 Communication Port

Modbus TCP port: 502

2.3 Unit ID

Default value: 200
Configurable range: 1–247

In Modbus TCP, the Unit ID is a logical identifier retained for RTU compatibility. It uses the same configuration parameter as the slave address used in RTU mode.

2.4 Register Definitions

2.4.1 Register Types

Register Type	Function	Function Code	Description
Input Registers	Read input registers	0x04	Read-only registers that return measurements or status information such as voltage, current, power, temperature, cumulative energy, etc.
Holding Registers	Read holding registers	0x03	Read/write registers. The master can read current configuration, current limits, mode status, etc.
Holding Registers	Write single holding register	0x06	The master writes a single configuration parameter or command, such as max current setting or start/stop charging.
Holding Registers	Write multiple holding registers	0x10	The master writes multiple consecutive registers at once, used for batch updates to configuration or structured parameter groups.

These four are the fundamental function codes recognized by IEC 61131-3, EN 61107, and the ISO Modbus specification, and are supported by almost all masters, PLCs, and EMS systems by default.

2.4.2 Register Address Planning (Address Map)

Principle	Description
Length	The address field in a Modbus frame is a 16-bit unsigned integer.
Layered partitioning	Partition by function: Identification → Station-level → Per connector. Keep the logic clear and easy to extend.
Unified starting point	All registers use logical addresses. Logical addressing typically starts at 0. The document shows both decimal and hexadecimal formats.
Alignment rule	32-bit data must start at an even address to avoid crossing register boundaries.
Reserved expansion space	Each area keeps gaps so future versions can add fields without breaking compatibility.
Character encoding	Each register is 2 bytes. Strings are fixed-length and are not padded with 0x00 for unused bytes.
Byte/Word order	Single-register byte order is Big-Endian. Multi-register data uses Little-Endian word order DCBA.
Access methods	Input uses 0x04. Holding registers are read with 0x03 and written with 0x06 single or 0x10 multiple.

2.4.3 Identification, Version, and Time (Input, 0x04)

Address	Name	Type	Unit	Access	Description
0000–0007 / 0x0000–0x0007	Brand	STRING(16)	—	RO	2 bytes per register, UTF-8/ASCII.
0008–0015 / 0x0008–0x000F	Model	STRING(16)	—	RO	Device model.
0016–0027 / 0x0010–0x001B	Serial Number	STRING(24)	—	RO	Device serial number.
0028–0035 / 0x001C–0x0023	Firmware Version	STRING(16)	—	RO	For example: 04.00.19.
0036 / 0x0024	Modbus Table Version	UINT16	—	RO	Mapping version number, for example 0x0100.
0037 / 0x0025	ConnectorCount	UINT16	—	RO	Number of connectors: 1 or 2.
0038–0039 / 0x0026–0x0027	Date	UINT32	YYYYMMDD	RO	32-bit even alignment. Example: 20251202.
0040–0041 / 0x0028–0x0029	Time	UINT32	HHMMSS	RO	Example: 155630 means 15:56:30.
0042 / 0x002A	Timezone	UINT16	minutes	RO	Example: UTC+2 → +120.
0044	Hardware version	STRING(16)	—	RO	Hardware version.
0043–0099	Reserved	—	—	—	Reserved for future identification, certificates, manufacturing info, etc.

2.4.4 Real-time Status and Metering (Input, 0x04)

Address	Name	Type	Unit	Access	Description
0100 / 0x0064	Chargepoint State	UINT16	—	RO	0: Available 1: Preparing 2: Charging 3: SuspendedEVSE 4: SuspendedEV 5: Finishing 6: Reserved 7: Unavailable 8: Faulted
0102–0103 / 0x0066–0x0067	Current L1	FLOAT32	A	RO	32-bit even alignment.
0104–0105 / 0x0068–0x0069	Current L2	FLOAT32	A	RO	—
0106–0107 / 0x006A–0x006B	Current L3	FLOAT32	A	RO	—
0108–0109 / 0x006C–0x006D	Voltage L1-N	FLOAT32	V	RO	—
0110–0111 / 0x006E–0x006F	Voltage L2-N	FLOAT32	V	RO	—
0112–0113 / 0x0070–0x0071	Voltage L3-N	FLOAT32	V	RO	—
0114–0115 / 0x0072–0x0073	Phase Angle L1	FLOAT32	°	RO	Phase angle referenced to L1-N.
0116–0117 / 0x0074–0x0075	Phase Angle L2	FLOAT32	°	RO	Phase angle referenced to L1-N.
0118–0119 / 0x0076–0x0077	Phase Angle L3	FLOAT32	°	RO	Phase angle referenced to L1-N.
0120–0121 / 0x0078–0x0079	Active Power L1	FLOAT32	W	RO	—
0122–0123 / 0x007A–0x007B	Active Power L2	FLOAT32	W	RO	—
0124–0125 / 0x007C–0x007D	Active Power L3	FLOAT32	W	RO	—
0126–0127 / 0x007E–0x007F	Active Power Total	FLOAT32	W	RO	—
0128–0129 / 0x0080–0x0081	Session Energy	FLOAT32	kWh	RO	Current session.
0130–0133 / 0x0082–0x0085	Lifetime Energy	UINT64	Wh	RO	Cumulative energy. 64-bit, 4 registers.
0134–0135 / 0x0086–0x0087	Fallback Current	FLOAT32	A	RO	Fallback current set via NexBlue App or cloud.
0136–0137 / 0x0088–0x0089	Max Charging Current	FLOAT32	A	RO	Maximum charging current set via NexBlue App or cloud.
0138 / 0x008A	Phase Charging	UINT16	—	RO	0: Adaptive 1: Force Single Phase 2: Force Three Phase
0137–0399 / 0x0088–0x018F	Reserved	—	—	—	Reserved for voltage, power factor, frequency, per-phase power, etc.

2.4.5 Control and Safety (Holding, read 0x03 / write 0x06 or 0x10)

Notes: If the charger AC power cycles, it will automatically revert to default values and must be written again.

Address	Name	Type	Unit	Access	Description
1000–1001 / 0x03E8–0x03E9	Current Limit	FLOAT32	A	RW	Station-level current limit. Default 16A. Range 0–32A.
1002–1003 / 0x03EA–0x03EB	Fallback Limit	FLOAT32	A	RW	Disconnect fallback current can only be set to 0–16. Values below 6 are treated as 0.
1004–1005 / 0x03EC–0x03ED	Fallback Timeout	UINT32	s	RW	Heartbeat timeout threshold. Default 5 minutes. Minimum 30 seconds. Maximum 30 minutes.
1006 / 0x03EE	IF_START	UINT16	—	RW	Start/Stop control 0: STOP 1: START
1007 / 0x03EF	Runtime Phase Mode	UINT16	—	RW	Values: 0: Adaptive 1: Force Single Phase 2: Force Three Phase Switching constraints: Recommended minimum interval between phase switches: 10 minutes Maximum 2 phase switches within any 1-hour period Maximum 6 phase switches during a single charging session
1008–1999	Reserved	—	—	—	Reserved for extensions.

2.4.6 Alarms and Errors (Error / Warning)

Address	Name	Type	Unit	Access	Description
0400 / 0x0190	Error Bitset	UINT16	—	RO	Bit0: CP voltage abnormal Bit1: phase line leakage Bit2: current abnormal / overcurrent Bit3: voltage abnormal / overvoltage or undervoltage Bit4: temperature abnormal / high or low Bit5: relay stuck Bit6: RCD self-test failed Bit7: CP diode short Bit8: PEN open Bit9: PE leakage Bit10: PE open Bit11: PP abnormal Bit12–15: reserved
0401 / 0x0191	Warning Bitset	UINT16	—	RO	Bit0: meter chip abnormal Bit1: inter-board communication abnormal Bit2: RFID RF abnormal Bit3: 868 RF abnormal Bit4: 4G module abnormal Bit5: cover open abnormal Bit6: reserved Bit7: TN system phase-loss abnormal Bit8: IT neutral overcurrent Bit9: grid abnormal Bit10: MID mode Bit11–15: reserved
0402 / 0x0192	Waiting Bitset	UINT16	—	RO	Bit0: fallback due to CT offline Bit1: fallback due to main unit offline Bit2: paused due to low-severity error / charging profile current is 0 via OCPP Bit3: host reduces current mid-charge Bit4: first request sent but host has not responded Bit5: load shedding protection active Bit6: fallback triggered by Modbus Bit6–15: reserved

Appendix

Function Codes

A function code in Modbus indicates what operation the master wants to perform on the slave. Each frame includes a 1-byte function code.

Hex	Meaning	Target
0x01	Read Coils	Bit outputs
0x02	Read Discrete Inputs	Bit inputs
0x03	Read Holding Registers	16-bit
0x04	Read Input Registers	16-bit
0x05	Write Single Coil	Bit
0x06	Write Single Holding Register	16-bit
0x0F	Write Multiple Coils	Bit
0x10	Write Multiple Holding Registers	16-bit

Summary of Common Modbus Data Types

Data Type	Registers Used	Bit Width	C Type	Meaning and Use	Typical Examples
UINT16	1	16-bit	uint16_t	Unsigned integer	Status codes, enums, counters, connector count.
INT16	1	16-bit	int16_t	Signed integer	Temperature, offsets, timezone.
UINT32	2	32-bit	uint32_t	Unsigned long integer	Timestamps, energy metering, second counters.
INT32	2	32-bit	int32_t	Signed long integer	Power, directional values.
FLOAT32	2	32-bit	float	Single-precision float, IEEE 754.	Current, voltage, power, energy, etc.
UINT64	4	64-bit	uint64_t	Very large integer	Total energy, cumulative metering.
STRING[n]	n/2	n × 8-bit	char[]	Text information	Brand, model, serial number, version number.