Update plugin_solax.py

Author: rosenrot00

custom_components/solax_modbus/plugin_solax.py

@@ -6595,6 +6595,7 @@ def value_function_battery_voltage_cell_difference(initval: int, descr: Any, dat
         register=0x1B,
         register_type=REG_INPUT,
         allowedtypes=HYBRID | GEN4 | GEN5 | GEN6,
+        entity_category=EntityCategory.DIAGNOSTIC,
     ),
     SolaXModbusSensorEntityDescription(
         name="Battery Capacity",