The gateway connects but the power register always reads zero.

Confirm Modbus TCP is actively enabled in the MAX.STORAGE web interface and not just configured. Some firmware versions require a save-and-restart cycle after enabling the interface. Also verify the unit ID in the portal matches the device setting exactly.

Why do I get an error when reading register 118?

Register 118 is a 32-bit int32 value spanning two consecutive 16-bit Modbus input registers (118 and 119). If your polling tool or a custom configuration requests only one register, the read will fail or return a garbage half-word. The ModbusCloud template handles this automatically with function code 4 and int32 type.

The reported power value seems inverted compared to the meter display.

The SolarMax MAX.STORAGE uses a signed convention for the grid power register: positive means the site is drawing power from the grid and negative means it is exporting. If your downstream system expects the opposite sign, apply a scaling factor of -1 in your dashboard formula rather than rewiring.

The ModbusCloud Gateway cannot reach the MAX.STORAGE on the network.

Check that the MAX.STORAGE unit has a static or DHCP-reserved IP address, since a lease change will break polling. Ensure no firewall or VLAN separation blocks TCP port 502 between the Gateway and the storage unit. Ping the device IP from a laptop on the same network segment to confirm basic reachability.

Free Modbus template: SolarMax MAX.STORAGE / MAX.STORAGE Ultimate (grid)

Name: SolarMax MAX.STORAGE / MAX.STORAGE Ultimate (grid)
Brand: SolarMax
SKU: f1c0e8c4-d035-495a-874f-e4a7bbbdef6e

The SolarMax MAX.STORAGE and MAX.STORAGE Ultimate are residential battery storage systems that combine a PV inverter, battery management, and grid interface in one unit. This ModbusCloud template connects to the device over Modbus TCP and reads the grid-connection power register, giving you a real-time signed watt value that shows whether the site is currently importing from or exporting to the grid. For installers and building owners, this single data point is the foundation for consumption tracking, export monitoring, and billing verification across single or multi-site portfolios.