diff --git a/custom_components/zaptec/binary_sensor.py b/custom_components/zaptec/binary_sensor.py
index 249dc7d..e9a9e90 100644
--- a/custom_components/zaptec/binary_sensor.py
+++ b/custom_components/zaptec/binary_sensor.py
@@ -34,11 +34,14 @@ def _update_from_zaptec(self) -> None:
         self._attr_available = True
 
 
-class ZaptecBinarySensorWithAttrs(ZaptecBinarySensor):
-    """Zaptec binary sensor with additional attributes."""
+class ZaptecActiveBinarySensor(ZaptecBinarySensor):
+    """Zaptec 'active' binary sensor for the main charger/installation device.
+
+    Uses the bare Zaptec object id as the unique id (without the entity key
+    suffix) to preserve the historical entity identity.
+    """
 
     def _post_init(self) -> None:
-        self._attr_extra_state_attributes = self.zaptec_obj.asdict()
         self._attr_unique_id = self.zaptec_obj.id
 
 
@@ -55,7 +58,7 @@ class ZapBinarySensorEntityDescription(ZaptecEntityDescription, BinarySensorEnti
         entity_category=const.EntityCategory.DIAGNOSTIC,
         icon="mdi:cloud",
         has_entity_name=False,
-        cls=ZaptecBinarySensorWithAttrs,
+        cls=ZaptecActiveBinarySensor,
     ),
     ZapBinarySensorEntityDescription(
         # The Zaptec API is not consistent with the naming of the usage of
@@ -77,7 +80,7 @@ class ZapBinarySensorEntityDescription(ZaptecEntityDescription, BinarySensorEnti
         entity_category=const.EntityCategory.DIAGNOSTIC,
         icon="mdi:cloud",
         has_entity_name=False,
-        cls=ZaptecBinarySensorWithAttrs,
+        cls=ZaptecActiveBinarySensor,
     ),
     ZapBinarySensorEntityDescription(
         key="is_online",
diff --git a/custom_components/zaptec/manager.py b/custom_components/zaptec/manager.py
index 79b9fc0..1a2c379 100644
--- a/custom_components/zaptec/manager.py
+++ b/custom_components/zaptec/manager.py
@@ -173,7 +173,9 @@ def create_entities_from_zaptec(
                 )
 
             elif isinstance(obj, Charger):
-                info = DeviceInfo()
+                # Expose the Zaptec device id as the device serial number, matching
+                # what the Zaptec app shows as the charger serial.
+                info = DeviceInfo(serial_number=obj.get("DeviceId"))
                 if obj.installation:
                     info["via_device"] = (DOMAIN, obj.installation.id)