Why does the power register always return zero or null?

The Junelight Modbus TCP interface must be explicitly activated by Siemens or your certified installer. If the interface has not been enabled, all register reads will fail silently or return zero. Confirm activation status with your Siemens service contact before troubleshooting further.

The Gateway connects to port 502 but reads time out. What is wrong?

Check that the Junelight and the ModbusCloud Gateway are on the same IP subnet and that no router or firewall is blocking port 502. Also verify the battery's IP address has not changed due to DHCP reassignment. Assigning a static IP to the Junelight resolves most persistent timeout issues.

Power values look correct in sign but are far too large or too small. Why?

The power register is a signed 32-bit integer spanning two consecutive 16-bit holding registers. If your client reads only one 16-bit word instead of two, the value will be incorrect. Confirm the ModbusCloud template is read as int32 across two registers starting at address 14.

Readings drop out periodically even though the network is stable. What causes this?

The Junelight's Modbus TCP server has a limited number of simultaneous connections. If another system, such as a home automation controller, already holds an open connection, the Gateway may be refused. Close unused connections or configure the other client to release connections between polls.

Free Modbus template: Siemens Junelight Smart Battery (grid)

Name: Siemens Junelight Smart Battery (grid)
Brand: Siemens
SKU: e0882df1-156a-4016-9ddb-8b966c37ef8d

The Siemens Junelight Smart Battery is a modular residential lithium-ion storage system designed to pair with rooftop PV installations. This Modbus TCP template reads the grid-side power register, capturing the real-time power flow between the battery system and the public grid. Positive values indicate import; negative values indicate export. With the ModbusCloud Gateway connected to the same network as the Junelight, you can log grid power continuously, build historical trend charts, and trigger alerts, giving installers and building owners a clear picture of household energy autonomy.