Description:
Device
- Charger: Compleo WallBe Eco 11kW AC
- Firmware: SL-01.04.21
- Modbus TCP Port: 502
- Unit ID: 0
Problem
Attempting to control the WallBe Eco via Modbus TCP. Reads work correctly across all register types. However all Modbus TCP writes are blocked — the device responds with:
Write output (holding) register failed: Illegal data address
Root Cause
HR 3872 (Modbus TCP Access) controls write access:
| Value |
Meaning |
| 0 |
Modbus TCP deactivated |
| 1 |
Modbus TCP whitelist |
| 2 |
No restrictions |
Current state:
[3872]: 0
This creates a chicken-and-egg problem — writes are blocked because HR 3872 = 0, but HR 3872 itself cannot be written because writes are blocked. The register is also not exposed in the web portal UI on this firmware version.
Newer firmware appears to expose a Modbus TCP Access dropdown under the Network tab — this section is absent on SL-01.04.21.
Secondary Blocker — D7 vs D10
- D7 (EN pin physical signal) is currently active — controls charging release at hardware level
- D10 (Register Enable Charging) must be enabled for Coil 400 to control charging via Modbus
- D10 is greyed out in the portal because D7 is active
- Unchecking D7 and checking D10 as two separate portal submits has not reliably taken effect
For full Modbus control all three layers are required:
HR 3872 = 2 → Modbus writes allowed
D10 enabled → Coil 400 is charging authority
Coil 400 = 1 → charging starts
What Was Tried
- Writing HR 3872 = 2 via mbpoll → Illegal data address
- Network tab in portal → no Modbus TCP section visible
- Hidden URLs (/modbus.html, /advanced.html) → not found
- Unchecking D7 → checking D10 via Config tab → D10 remains greyed out
Questions
- Is there a way to set HR 3872 = 2 on firmware SL-01.04.21 without Modbus write access?
- Is the missing Modbus TCP Access UI a firmware limitation that requires an update, or a hardware/configuration issue?
- Is there a hidden portal page or factory procedure to unlock Modbus TCP writes on this firmware?
- Who is the right contact — Compleo or — for firmware support on this device, and is a newer firmware available that resolves this?
Environment
- Testing tool: mbpoll 1.0-0
Description:
Device
Problem
Attempting to control the WallBe Eco via Modbus TCP. Reads work correctly across all register types. However all Modbus TCP writes are blocked — the device responds with:
Write output (holding) register failed: Illegal data address
Root Cause
HR 3872 (Modbus TCP Access) controls write access:
Current state:
[3872]: 0
This creates a chicken-and-egg problem — writes are blocked because HR 3872 = 0, but HR 3872 itself cannot be written because writes are blocked. The register is also not exposed in the web portal UI on this firmware version.
Newer firmware appears to expose a Modbus TCP Access dropdown under the Network tab — this section is absent on SL-01.04.21.
Secondary Blocker — D7 vs D10
For full Modbus control all three layers are required:
HR 3872 = 2 → Modbus writes allowed
D10 enabled → Coil 400 is charging authority
Coil 400 = 1 → charging starts
What Was Tried
Questions
Environment