Hager via Modbus RTU (RS-485)
This guide describes step by step how to connect a Hager Witty EV charger to the Currentt Navigator via Modbus RTU over RS-485.
Also see: For connection via the network (Modbus TCP), see the guide Hager Modbus TCP.
✅ Compatible models
| Model | Type | RS-485 Modbus |
|---|---|---|
| Witty One | Socket / Fixed cable | Via XVA245 communication card |
| Witty Plus | Socket / Fixed cable | Built in (RJ45 connector 1) |
The Witty One has no RS-485 Modbus input as standard. It is added with the optional XVA245 communication card, which is fitted into one of the option card slots of the EV charger. This card adds an RS-485 Modbus input, an Ethernet input and WiFi.
The Witty Pro has two Ethernet ports but no built-in RS-485 Modbus input. Connect this model via Modbus TCP.
🧰 Requirements
- Currentt Navigator Pro (with RS-485 Modbus connection)
- Shielded 2-wire RS-485 cable, AWG 23 or AWG 24 (Hager HTG465H or equivalent: 2 twisted pairs, 0.25 mm², shielded)
- For the Witty Plus: RJ45 connector (T568A or T568B) for the EV charger side
- For the Witty One: XVA245 communication card
- Phillips screwdriver (for opening the enclosure)
⚠️ Safety warnings
Always disconnect the EV charger from the power supply before opening the enclosure. Switch off the circuit breaker and the residual-current device of the charging circuit, and verify with a voltage tester that no voltage is present.
🪛 Installation instructions
Step 1: Disconnect the EV charger from the power supply
- Switch off the charging circuit in the distribution board (circuit breaker and residual-current device)
- Verify with a voltage tester that the EV charger is de-energised
- Open the enclosure of the EV charger according to the supplied installation manual
Step 2: Connect the RS-485 cable
The RS-485 connection differs per model. Follow the instructions for your EV charger.
Witty Plus: RJ45 connector 1
The Witty Plus has two RJ45 connectors. Only connector 1 supports RS-485 Modbus; connector 2 is Ethernet only.
- Lead the RS-485 cable into the enclosure through the cable gland
- Fit an RJ45 connector to the cable according to the pin definition below
- Plug the RJ45 connector into connector 1 (the RS-485 Modbus connection)
- Connect the other end to the RS-485 Modbus connection on the Currentt Navigator using the supplied plug-in connector
| Pin | Signal | Connection on the Currentt Navigator |
|---|---|---|
| 1 | — | — |
| 2 | — | — |
| 3 | — | — |
| 4 | Data + | A+ |
| 5 | Data − | B− |
| 6 | — | — |
| 7 | — | — |
| 8 | 0 V (brown wire) | G (see ground connection) |
Always use one wire pair from the same twisted pair for Data + and Data − (pins 4 and 5 form a pair in both T568A and T568B). Using two wires from different pairs leads to communication errors.
Witty One: XVA245 communication card
On the Witty One, the RS-485 connection runs via the XVA245 communication card. This card has a screw terminal for the RS-485 Modbus input.
- Fit the XVA245 card into one of the option card slots according to the card's instructions
- Lead the RS-485 cable into the enclosure through the cable gland
- Connect the wires to the RS-485 terminals on the card:
| Terminal | Signal | Connection on the Currentt Navigator |
|---|---|---|
| + | Data + | A+ |
| − | Data − | B− |
| 0V | Reference (0 V) | G (see ground connection) |
| GND | Cable shield | Shield |
- Connect the other end to the RS-485 Modbus connection on the Currentt Navigator using the supplied plug-in connector
The XVA245 contains electronic components that can be damaged by static electricity. Wear an antistatic bracelet when fitting the card, or first touch an earthed metal point. Keep the card in its antistatic packaging until use.
The RS-485 Modbus input of the XVA245 supports a cable length of up to 1200 m (AWG 23 or AWG 24, without stripping the wires).
Points to note for both models
Swapping Data + and Data − leads to communication errors. If you cannot establish a connection, swap the two wires.
Connect the ground (0 V) on one side only: either to the Currentt Navigator or to the EV charger — but never on both sides. Connecting ground on both sides can cause a ground loop, leading to communication errors.
Do not use R02V cable or twisted telephone cable for the RS-485 connection. Hager explicitly excludes these cable types.
Step 3: Set the termination resistor
Both models have a switch for the built-in 120Ω termination resistor: on the Witty Plus next to the RJ45 connectors, on the Witty One on the XVA245 card.
- Set the switch to ON when the EV charger is the last device on the RS-485 bus
- Set the switch to OFF when other devices are connected beyond the EV charger on the same bus
The RS-485 connection on the Currentt Navigator Pro also contains an internal 120Ω termination resistor, which can be enabled or disabled via the software. It is enabled by default. See RS-485 Modbus.
Step 4: Close the enclosure and switch on
- Secure the cable with the cable clamp and tighten the cable gland
- Close the enclosure of the EV charger
- Switch the charging circuit back on in the distribution board
- Wait until the EV charger has started up
Are you using both Modbus RTU and a wired network connection? Connect the Ethernet cable to connector 2, so that connector 1 remains free for RS-485 Modbus.
Step 5: Configuration in the Currentt Navigator
After connecting the RS-485 cable, the EV charger must be added in the Currentt Navigator.
Via the installation wizard (recommended)
- Click the settings icon (top right of the screen)
- Choose Installation wizard
- Follow the steps on the screen
Manual configuration
- Click the settings icon (top right of the screen)
- Go to Components
- Click the + button in the EV chargers section
- Select Hager
- Under Communication, enter the connection details:
| Parameter | Value |
|---|---|
| Physical connection | RS-485 |
| Modbus address | 1 (default) |
| Baud rate | Use the baud rate configured on the EV charger |
| Parity | Disable (no parity) |
- Click Save
The Witty supports a baud rate of 1200 to 38400 baud. Set the same baud rate within the supported range on the EV charger and the Navigator.
Make sure every device on the RS-485 bus has a unique Modbus address. If you connect multiple devices to the same bus, give the EV charger an address that is not yet in use.
📋 Settings summary
| Parameter | Value |
|---|---|
| Connection | RS-485 (Modbus RTU) |
| Protocol | Modbus RTU |
| Witty Plus connection | RJ45 — connector 1: pin 4 = Data + (A+), pin 5 = Data − (B−), pin 8 = 0 V |
| Witty One connection | XVA245 terminals: + = Data + (A+), − = Data − (B−), 0V, GND = shield |
| Cable | Shielded 2-wire, AWG 23 or AWG 24 (Hager HTG465H or equivalent) |
| Max. cable length | 1200 m |
| Termination resistor | 120Ω, switch to ON on the last device on the bus |
| Modbus address | 1 (default) |
| Baud rate | 1200 – 38400 baud |
| Data bits | 8 |
| Parity | None (disable) |
🛟 Troubleshooting
| Problem | Possible cause | Solution |
|---|---|---|
| No connection | Witty One without communication card | Check that the XVA245 communication card is fitted; without this card the Witty One has no RS-485 input |
| No connection | Cable in the wrong RJ45 connector (Witty Plus) | Plug the RS-485 cable into connector 1; connector 2 is Ethernet only |
| No connection | Data + and Data − swapped | Swap the two wires |
| No connection | Baud rate outside the supported range | Set a baud rate between 1200 and 38400 baud, identical on the EV charger and the Navigator |
| No connection | Wrong Modbus address | Check that the Modbus address in the Navigator matches that of the EV charger |
| No connection | Parity is not disabled | Set the parity in the Navigator to Disable |
| No connection | Wires from different twisted pairs used | Use one wire pair from the same twisted pair for Data + and Data − |
| Unreliable communication | Termination resistor set incorrectly | Set the 120Ω switch to ON if the EV charger is the last device on the bus, otherwise to OFF |
| Unreliable communication | Wrong cable type | Use shielded 2-wire RS-485 cable; R02V and twisted telephone cable are not permitted |
| Unreliable communication | Ground connected on both sides | Connect the ground (0 V) on one side only |
| Unreliable communication | Cable too long or damaged | Use a shorter cable or check for damage |
| Address conflict | Multiple devices with the same Modbus address | Give every device on the RS-485 bus a unique Modbus address |
| EV charger does not respond | EV charger not switched on | Check that the charging circuit is switched on and the EV charger has started up |