Heidelberg Energy
The Heidelberg Energy Control is an AC wallbox for charging electric and hybrid vehicles at up to 11 kW over a Type 2 cable. It exposes a Modbus RTU interface over RS-485, allowing external load management systems to read the IEC 61851-1 charging state and active power, and to write the maximum current setpoint, failsafe current, watchdog timeout, and standby mode. This ModbusCloud template gives installers live charge-session visibility and dynamic current control from a single portal, without additional proprietary software.
- Protocol
- Modbus RTU
- Connection
- RS485
- Registers
- 6, read and write
- Brand
- Heidelberg
- Last updated
Registers (6)
2 read, 4 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| heidelberg_state | Read | ||||
| active_power | W | Read | |||
| watchdog_time | Write | ||||
| standby | Write | ||||
| max_current | A | Write | |||
| failsafe_current | A | Write |
Loading registers…
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Use cases
- Monitor active power in real time to verify that charging sessions stay within contracted grid capacity.
- Track the IEC 61851-1 charging state to detect vehicles stuck in an error or derating condition.
- Alert on active power readings above zero while max_current is set to zero, indicating a control fault.
- Compare actual charging power across multiple Heidelberg Energy Control units on one site dashboard.
- Verify that failsafe_current is set to a safe non-zero value before enabling automated load-control scripts.
Installation
Enable Modbus RTU on the wallbox by setting the internal DIP switches to configure the unit as a Modbus server and to select the desired slave ID and current range, following the wallbox installation manual.
Wire the RS-485 bus: connect the A and B terminals inside the wallbox to the corresponding A and B terminals on the ModbusCloud Gateway, using twisted-pair cable; add a 120-ohm termination resistor at each end of the bus.
In the ModbusCloud portal, add the Gateway, import the Heidelberg Energy Control template, and set the unit ID to match the slave address configured on the DIP switches (default is 1).
Spot-check the connection by reading the heidelberg_state register: a value of 2 (state A1, no vehicle) confirms communication; then write 4 to the standby register to keep the wallbox responsive while no vehicle is plugged in.
Things to watch for
The wallbox stops responding after a few minutes with no vehicle plugged in.
The wallbox enters standby mode by default when no vehicle is connected, which drops the RS-485 bus and causes Modbus timeouts. Write the value 4 to the standby register (address 258) to disable standby. This setting survives power cycles, so you only need to do it once.
Why does the wallbox blink and refuse to charge after a gateway restart?
The watchdog register (address 257) defaults to 15000 ms. If no Modbus frame arrives within that window, the wallbox enters timeout mode and stops charging. ModbusCloud polls at most once per minute, every 5 minutes by default, so it cannot meet this window. Write 0 to register 257 to disable the watchdog when you use ModbusCloud.
The max_current register reads back zero and no charging starts.
Register 261 does not retain its value after a power cycle or standby exit; the default is 0, which locks out charging. Your control system must write a value in the range 60 to 160 (representing 6.0 A to 16.0 A) to register 261 on every startup before charging can begin.
Is it safe to write large current values to the max_current or failsafe_current register?
Write only values within the range configured by the hardware DIP switches, typically 60 to 160 (6 A to 16 A). Writing 0 to max_current silently disables charging without notifying the user. Setting failsafe_current to 0 places the wallbox into an error state on communication loss; always configure a non-zero safe fallback value.
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