E3/DC e3dc (battery)
The E3/DC e3dc is a home power plant combining a PV inverter and integrated battery storage, designed for residential self-consumption. This Modbus TCP template reads the two core battery registers: instantaneous power at address 40069 (positive values indicate discharge, negative values indicate charge) and state of charge at address 40082. Connecting these via the ModbusCloud Gateway gives installers a live view of battery behaviour in the portal, enabling charge-cycle tracking and threshold alerts without additional hardware.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 2, read only
- Brand
- E3/DC
- Last updated
Registers (2)
2 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| power | W | Read | |||
| soc | % | Read |
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Use cases
- Monitor battery state of charge daily to verify the E3/DC e3dc reaches expected charge levels by evening.
- Track battery power sign changes over time to identify unusual charging or discharging patterns.
- Alert on sustained negative power values during daylight hours to detect inverter or charge-controller faults.
- Compare state of charge trends across multiple E3/DC e3dc sites from a single multi-site portal view.
- Report daily discharge depth over weeks to assess battery capacity retention across seasons.
Installation
Enable Modbus TCP on the E3/DC unit: navigate to the device menu under Functions or Smart Home, activate Modbus, then select the E3/DC or E3/DC Simple-Mode protocol and confirm TCP is enabled on port 502.
Connect the ModbusCloud Gateway to the same LAN as the E3/DC unit, ensuring both devices are on the same IP subnet and port 502 is not blocked by a local firewall.
In the ModbusCloud portal, add a new device, import the E3/DC e3dc (battery) template, and set the Modbus unit ID to 1 (the E3/DC default) unless you changed it in the device menu.
Verify the connection by checking the live value for register 40082 (soc) in the portal: a reading between 0 and 100 confirms polling is working correctly.
Things to watch for
Register 40069 returns zero even when the battery is active. Why?
Modbus TCP must be explicitly enabled on the E3/DC unit and the correct protocol (E3/DC or E3/DC Simple-Mode) must be selected in the device menu. If Modbus is enabled but the protocol is set to a different mode, power registers return zero or garbage values. Recheck the protocol selection and restart the Modbus interface on the unit.
The power value at 40069 looks correct at low loads but wraps to a large positive number at high charge rates. What is happening?
Register 40069 is typed as int32 spanning two 16-bit Modbus registers. Some polling clients read only the first 16-bit word (uint16), which overflows above 32,767 W. Confirm your client reads two consecutive registers and decodes them as a signed 32-bit integer. The ModbusCloud Gateway handles this correctly with the int32 type in the template.
The gateway shows no connection to the E3/DC unit at all. Where should I start?
Confirm the E3/DC unit has an IP address reachable from the ModbusCloud Gateway (same subnet or routed). Verify port 502 is open: the E3/DC Modbus interface is unencrypted and listens only on the local network. After any change to the Modbus settings on the unit, the interface may need a few seconds to restart before accepting connections.
SOC at register 40082 reads a split or unexpected value. Is the data type wrong?
In the E3/DC Simple-Mode register map, address 40082 can carry autarky and self-consumption as two packed uint8 values in some firmware versions, while the battery SOC is a standard uint16 in others. This template uses uint16, which is correct for the battery SOC channel targeted by the OpenEMS implementation. If values appear doubled or split, confirm the firmware version on the unit and that the Simple-Mode protocol is active.
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