SolarMax MAX.STORAGE / MAX.STORAGE Ultimate (grid)
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.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 1, read only
- Brand
- SolarMax
- Last updated
Registers (1)
1 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| power | W | Read |
Loading registers…
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor real-time grid import and export power to verify self-consumption performance of the SolarMax MAX.STORAGE installation.
- Alert on sustained grid import during daylight hours to detect underperforming PV or unexpected load increases.
- Track daily grid-import totals over time to compare against utility invoices and identify billing discrepancies.
- Verify that the SolarMax MAX.STORAGE Ultimate is correctly limiting grid export to comply with local grid-operator requirements.
- Compare grid power readings across multiple sites in the ModbusCloud portal to benchmark storage system performance.
Installation
Enable Modbus TCP on the SolarMax MAX.STORAGE or MAX.STORAGE Ultimate through the device web interface, under the communication or Modbus section, and note the assigned IP address.
Connect the ModbusCloud Gateway to the same local network as the MAX.STORAGE unit, ensuring the Gateway can reach the device IP on Modbus TCP port 502.
In your ModbusCloud portal, add the Gateway, import the SolarMax MAX.STORAGE template, and set the unit ID to match the value configured on the device (default is typically 1).
Spot-check the live reading for the power register in the portal dashboard and confirm the sign convention: a positive value indicates grid import and a negative value indicates grid export.
Things to watch for
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.
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