The Delta AC MAX Basic is a Mode 3 AC wallbox for electric vehicle charging, available in 7 kW (single-phase), 11 kW and 22 kW (three-phase) variants. It communicates with TapHome via Modbus RTU over RS-485, exposing charger and EVSE status registers, real-time power and energy metering, and two writable control registers for charging power limit and suspend/resume.

The AC MAX Basic supports a single EVSE connector. EVSE registers use an offset-based addressing scheme (EVSE 1 = base register + 1000).

Hardware connection

RS-485 wiring

The RS-485 terminal is located on the control board inside the wallbox. Remove the front and middle covers (Torx T20) to access the board.

Connect two wires from TapHome to the RS-485 terminal:

• Pin 4 (RS485 D+) –> A+/D+ on TapHome
• Pin 5 (RS485 D-) –> B-/D- on TapHome

The Delta AC MAX Basic does not expose a dedicated GND pin on the RS-485 terminal. If communication is unstable, verify that both devices share a common ground reference through the mains PE conductor.

Configuration

DIP switch settings

Six DIP switches on the control board configure the charger behavior. The DIP switches are accessible after removing the front and middle covers.

Maximum current settings (Pins 4/5/6):

* For 16 A models, settings above 16 A fall back to 6 A.

Set the maximum current DIP switches before commissioning. Some vehicles do not initiate a charging session at 6 A (the default).

Modbus communication parameters

The default RS-485 settings are:

• Baud rate: 19200
• Data bits: 8
• Parity: None
• Stop bits: 1
• Slave ID: 1 (configurable via AC MAX App)

The Modbus slave ID and baud rate can be changed via Bluetooth using the Delta AC MAX App (password: 0000). Available baud rates are 9600, 19200 and 38400.

The Modbus register table document mentions 115200 baud for RTU chargers, but the installation manual specifies 19200 as the default. The actual default on the AC MAX Basic is 19200. If communication fails, verify the baud rate setting in the AC MAX App.

Device capabilities

Charger and EVSE status

The template provides three status indicators:

• Charger State — overall charger condition read from register A:100: Not ready (0), Operational (1), or Faulted (2)
• EVSE Condition — OCPP-based EVSE status read from register A:1000 with 10 states: Unavailable, Available, Occupied, Preparing, Charging, Finishing, Suspended EV, Suspended EVSE, Not ready, Faulted
• Charge State — charging process state read from register A:1001 with states from “not started” through “charging” to “completed” or “error”

Power and energy metering

Real-time electrical measurements from the EVSE:

• Charging Power — instantaneous charging power in watts (A:1005)
• Output Voltage — charging voltage in volts (A:1003, scaled /10)
• Output Current — charging current in amps (A:1007, scaled /100)
• Charged Energy — energy transferred to the EV during the current session in Wh (A:1019)
• Total Power Consumption — total power consumption at the grid connection in watts (A:1047)
• Charging Time — duration of the current charging session in minutes (A:1017, converted from seconds /60)

Charging control

Two writable holding registers allow active charging management:

• Charging Power Limit (H:1600) — sets the maximum charging power in watts. Writing 0xFFFFFFFF removes the limit (displayed as no value). This register enables integration with home energy management systems to dynamically adjust charging power based on available capacity.
• Suspend Charging (H:1602) — pauses (1) or resumes (0) the charging session without disconnecting the vehicle. The charging cable remains locked while suspended.

Additional capabilities

The AC MAX also exposes registers for per-phase grid power consumption (L1, L2, L3), per-phase EVSE current, EVSE total current, and IEC 62196 plug state. Communication timeout registers (H:201-203) allow configuring a safety fallback power level if no Charging Power Limit command is received within a specified interval. These can be added in a future template update.

The communication timeout feature (registers H:201-203) is useful for safety: if TapHome loses communication with the charger, a preconfigured fallback power level is applied automatically. This can be configured directly via Modbus writes to H:201 (enable), H:202 (timeout in seconds, 0-600) and H:203 (fallback power in watts).

Troubleshooting

No Modbus communication

1. Verify RS-485 wiring: Pin 4 = D+, Pin 5 = D-
2. Confirm baud rate is 19200 in both TapHome and the charger (check via AC MAX App, password: 0000)
3. Verify the Slave ID matches between TapHome and the charger
4. Check that the charger is powered and the LED indicator shows blue (standby) or another active state — black means power off

Charging Power Limit has no effect

Community reports indicate that writing to the Charging Power Limit register (H:1600) may not produce an observable effect on some firmware versions. Ensure the charger firmware is up to date. The AC MAX App can be used to update firmware via Bluetooth.

LED indicator reference

Fault codes (red flashes):