SDM120 CT meter ID fix
Can't change the Modbus ID on an SDM120 CT meter? Here's the workaround, plus the newer meter variant with a user-changeable ID.
Updated 1 June 2026
The Eastron SDM120 is the single-phase CT meter commonly paired with Deye hybrids. The classic gotcha: the inverter expects the meter at a specific Modbus address, but the meter ID won’t change.
What’s going on
- Deye firmware polls the external meter at a fixed Modbus ID and 9600 baud.
- Some SDM120 variants ship with the address effectively locked, so the usual menu route to change it doesn’t stick — the meter answers on the wrong ID and the inverter sees “no meter”.
The workaround
- Confirm the meter is wired and powered (the display is lit) and RS485 A/B are correct — see smart meter wiring.
- Enter the meter’s setup menu (hold the button per the Eastron label) and set:
- Baud rate: 9600
- Address / ID: the value the inverter expects (commonly 1)
- If the address won’t save, the unit is the locked variant.
The proper fix
Use the newer meter variant with a user-changeable ID — the SDM120CT-MID style unit — which lets you set the Modbus address from the meter keypad. Set it to the inverter’s expected ID, 9600 baud, and it’s recognised immediately.
Keep one known-good meter in the van. Swapping a locked SDM120 for the user-settable variant is usually faster on site than fighting the menu.
Still no meter comms after this? See SDM120 / external meter not communicating.
