diff --git a/homewizard_energy/models.py b/homewizard_energy/models.py
index 783a82d..1e76086 100644
--- a/homewizard_energy/models.py
+++ b/homewizard_energy/models.py
@@ -701,8 +701,8 @@ class Permissions(StrEnum):
             "deserialize": lambda x: Batteries.Mode.__members__.get(x.upper(), None)
         },
     )
-    permissions: list[Permissions] = field(
-        default_factory=list,
+    permissions: list[Permissions] | None = field(
+        default=None,
         metadata={
             "deserialize": lambda lst: [
                 perm
@@ -710,6 +710,8 @@ class Permissions(StrEnum):
                 if (perm := Batteries.Permissions.__members__.get(item.upper(), None))
                 is not None
             ]
+            if lst is not None
+            else None
         },
     )
     power_w: float = field()
@@ -720,21 +722,34 @@ class Permissions(StrEnum):
 
     @classmethod
     def __post_deserialize__(cls, obj: Batteries) -> Batteries:
-        """Set correct mode based on permissions after deserialization."""
+        """Set correct mode based on permissions after deserialization.
+        If permissions is missing and mode is ZERO, keep mode as ZERO for backwards compatibility.
+        If permissions is present (even if empty), apply the mapping logic.
+        """
         # Only adjust if mode is ZERO
-        if obj.mode == cls.Mode.ZERO:
-            perms = set(obj.permissions)
-            if perms == {cls.Permissions.CHARGE_ALLOWED}:
-                obj.mode = cls.Mode.ZERO_CHARGE_ONLY
-            elif perms == {cls.Permissions.DISCHARGE_ALLOWED}:
-                obj.mode = cls.Mode.ZERO_DISCHARGE_ONLY
-            elif perms == {
-                cls.Permissions.CHARGE_ALLOWED,
-                cls.Permissions.DISCHARGE_ALLOWED,
-            }:
-                obj.mode = cls.Mode.ZERO
-            elif perms == set():
-                obj.mode = cls.Mode.STANDBY
+        if obj.mode != cls.Mode.ZERO:
+            return obj
+
+        # Detect if 'permissions' was present in the original data
+        # If using mashumaro, the original dict is not available here, so we infer:
+        # If permissions is None, treat as 'not provided'. If it's an empty list, treat as 'provided but empty'.
+        if obj.permissions is None:
+            # Permissions not provided, keep mode as ZERO (backwards compatibility)
+            return obj
+
+        perms = set(obj.permissions)
+        if perms == {cls.Permissions.CHARGE_ALLOWED}:
+            obj.mode = cls.Mode.ZERO_CHARGE_ONLY
+        elif perms == {cls.Permissions.DISCHARGE_ALLOWED}:
+            obj.mode = cls.Mode.ZERO_DISCHARGE_ONLY
+        elif perms == {
+            cls.Permissions.CHARGE_ALLOWED,
+            cls.Permissions.DISCHARGE_ALLOWED,
+        }:
+            obj.mode = cls.Mode.ZERO
+        elif perms == set():
+            obj.mode = cls.Mode.STANDBY
+
         return obj
 
 
diff --git a/tests/v2/__snapshots__/test_v2_batteries.ambr b/tests/v2/__snapshots__/test_v2_batteries.ambr
index a2e55dc..0aa593d 100644
--- a/tests/v2/__snapshots__/test_v2_batteries.ambr
+++ b/tests/v2/__snapshots__/test_v2_batteries.ambr
@@ -6,5 +6,8 @@
   Batteries(mode=<Mode.ZERO: 'zero'>, permissions=[<Permissions.CHARGE_ALLOWED: 'charge_allowed'>, <Permissions.DISCHARGE_ALLOWED: 'discharge_allowed'>], power_w=-404.0, target_power_w=-400.0, max_consumption_w=1600.0, max_production_w=800.0, battery_count=2)
 # ---
 # name: test_batteries[HWE-P1-fixtures0]
+  Batteries(mode=<Mode.ZERO: 'zero'>, permissions=None, power_w=-404.0, target_power_w=-400.0, max_consumption_w=1600.0, max_production_w=800.0, battery_count=None)
+# ---
+# name: test_batteries[HWE-P1-fixtures0].1
   Batteries(mode=<Mode.ZERO: 'zero'>, permissions=[<Permissions.CHARGE_ALLOWED: 'charge_allowed'>, <Permissions.DISCHARGE_ALLOWED: 'discharge_allowed'>], power_w=-404.0, target_power_w=-400.0, max_consumption_w=1600.0, max_production_w=800.0, battery_count=2)
 # ---
diff --git a/tests/v2/fixtures/HWE-P1/batteries_2_1_0.json b/tests/v2/fixtures/HWE-P1/batteries_2_1_0.json
new file mode 100644
index 0000000..47f0eae
--- /dev/null
+++ b/tests/v2/fixtures/HWE-P1/batteries_2_1_0.json
@@ -0,0 +1,7 @@
+{
+    "mode": "zero",
+    "power_w": -404,
+    "target_power_w": -400,
+    "max_consumption_w": 1600,
+    "max_production_w": 800
+}
diff --git a/tests/v2/fixtures/HWE-P1/batteries_2_2_0.json b/tests/v2/fixtures/HWE-P1/batteries_2_2_0.json
new file mode 100644
index 0000000..cb36b2d
--- /dev/null
+++ b/tests/v2/fixtures/HWE-P1/batteries_2_2_0.json
@@ -0,0 +1,9 @@
+{
+    "mode": "zero",
+    "permissions": ["charge_allowed", "discharge_allowed"],
+    "battery_count": 2,
+    "power_w": -404,
+    "target_power_w": -400,
+    "max_consumption_w": 1600,
+    "max_production_w": 800
+}
diff --git a/tests/v2/test_v2_batteries.py b/tests/v2/test_v2_batteries.py
index 91deb24..46a882c 100644
--- a/tests/v2/test_v2_batteries.py
+++ b/tests/v2/test_v2_batteries.py
@@ -15,7 +15,7 @@
 @pytest.mark.parametrize(
     ("model", "fixtures"),
     [
-        ("HWE-P1", ["batteries"]),
+        ("HWE-P1", ["batteries_2_1_0", "batteries_2_2_0"]),
         ("HWE-KWH1", ["batteries"]),
         ("HWE-KWH3", ["batteries"]),
     ],
@@ -109,6 +109,9 @@ def test_batteries_update_modes_and_permissions(
         (Batteries.Mode.ZERO, [], Batteries.Mode.STANDBY),
         (Batteries.Mode.STANDBY, [], Batteries.Mode.STANDBY),
         (Batteries.Mode.TO_FULL, [], Batteries.Mode.TO_FULL),
+        (Batteries.Mode.ZERO, None, Batteries.Mode.ZERO),
+        (Batteries.Mode.STANDBY, None, Batteries.Mode.STANDBY),
+        (Batteries.Mode.TO_FULL, None, Batteries.Mode.TO_FULL),
     ],
 )
 def test_set_mode_based_on_permissions(mode, permissions, expected_mode):