Support disconnected Powerwall configuration (#67325)

Co-authored-by: J. Nick Koston <nick@koston.org>

homeassistant/components/powerwall/binary_sensor.py

@@ -110,6 +110,15 @@ class PowerWallChargingStatusSensor(PowerWallEntity, BinarySensorEntity):
     _attr_name = "Powerwall Charging"
     _attr_device_class = BinarySensorDeviceClass.BATTERY_CHARGING
 
+    @property
+    def available(self) -> bool:
+        """Powerwall is available."""
+        # Return False if no battery is installed
+        return (
+            super().available
+            and self.data.meters.get_meter(MeterType.BATTERY) is not None
+        )
+
     @property
     def unique_id(self) -> str:
         """Device Uniqueid."""