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v5.32
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Master-Slave Setup

Most public Charging Stations have two connectors.
Building a double Charging Station powered by Bender Charge Controllers requires two Charge Controllers per Charging Station (one for each connector).

The Master-Slave feature allows you to form an interconnected unit out of 2 Charge Controllers within a chassis, that acts as a single Charging Station when interfacing with EV drivers and external systems, such as Backends.
One of the two Charge Controllers will be the Master Charge Controller.

The Master is in charge of most control functions and will serve as the sole interface to the outside world.
To achieve a harmonious system the two Charge Controllers need to be configured to be a Master Charge Controller, and a Slave Charge Controller respectively.

1. Requirements​

Ensure that

  • Both Charge Controllers have the same controller firmware version. (Check the number at the top right of the Config UI)
  • Both Charge Controllers have the Config UI set as the default. See here.

2. Configuration​

1 Wiring

  1. Run a USB cable from the Master Charge Controller's CONFIG USB port to one of the Slave Charge Controller's USB host ports.
tip

This is also how an installer would from now on connect to the charging station to access the configuration interface.

  1. Run a USB cable from the Slave Charge Controller's CONFIG USB port to your computer.

2 Configuring the Master Controller

  1. Connect the Master Charge Controller to your computer using a micro USB cable through the CONFIG USB port.
  2. Log in to the Legacy Config UI using the default Manufacturer Login Credentials
  3. Under Manufacturer (http://192.168.123.123/legacy/manufacturer/manufacturer), set Master/Slave Mode to Master.
  4. At the bottom of the Legacy Config UI, click to apply the changes

3 Configuring the Slave Controller

  1. Connect the Slave Charge Controller to your computer using a micro USB cable through the CONFIG USB port.
  2. Log in to the Legacy Config UI using the default Manufacturer Login Credentials
  3. Under Manufacturer (http://192.168.123.123/legacy/manufacturer/manufacturer), set Master/Slave Mode to Slave.
  4. At the bottom of the Legacy Config UI, click to apply the changes

4 Accessing the Controllers

3. Accessing the Master and Slave Controllers​

Access the Slave and Master Charge Controller like so from now on:

Master Controller
Slave Controller
#

4. Port Forwarding Limitations in Master-Slave Setups​

In Master-Slave setups, the Slave connects to the Master via an internal, non-routed network. While some ports are forwarded to the Master's network interface, the Slave cannot access other devices on the Master's external network.

This means, for example, that the Slave cannot communicate with Modbus TCP meters connected to the Master’s network. As a result, the Slave cannot use Modbus TCP meters as primary meters.

Component
Description
#
Master Network

Includes devices such as Modbus meters and other LAN-connected equipment.

#
Master Controller

Provides port forwarding into its internal network, exposing services that the Slave Controller can use.

#
Slave Controller

Connects to the Master's internal network. Most network-related tasks are handled by the Master Controller, including relaying all OCPP backend communication for the Slave.

4.1. When to use Single Feed mode​

Single Feed mode applies when a Double Charging Station (e.g. 2×22 kW) is connected using a single supply line that cannot provide the full combined power for both connectors. For example, if the line is rated for only 22 kW:

  • A single EV can charge at the full 22 kW when the second point is idle.
  • When both connectors are in use, power is shared (e.g. 2×11 kW).

In setups like this, enabling Single Feed is required. Without it, the system assumes each connector has access to full power at all times, which can result in:

  • Overloading the supply line, and
  • Incorrect application of current limits

4.2. Enabling Single Feed mode​

If the Double Charging Station is equipped with a single feed, set the following setting on both the Master Charge Controller and Slave Charge Controller:

  1. Log in to the Legacy Config UI using the default Manufacturer Login Credentials
  2. Under Manufacturer set Charging Station with single feed to On (the setting can be found near the bottom of the page)
  3. At the bottom of the Legacy Config UI, click to apply the changes
  4. Repeat this for the second Charge Controller of the Double Charging Station

The Double Charging Station will now share the available current Charging Station Installation Current Limit [A] between Master and Slave equally as soon as both are connected to an EV.