diff --git a/custom_components/bms_ble/plugins/jikong_bms.py b/custom_components/bms_ble/plugins/jikong_bms.py
index 064cd99..98c408b 100644
--- a/custom_components/bms_ble/plugins/jikong_bms.py
+++ b/custom_components/bms_ble/plugins/jikong_bms.py
@@ -37,6 +37,7 @@ class BMS(BaseBMS):
     HEAD_RSP: Final = bytes([0x55, 0xAA, 0xEB, 0x90])  # header for responses
     HEAD_CMD: Final = bytes([0xAA, 0x55, 0x90, 0xEB])  # header for commands (endiness!)
     BT_MODULE_MSG: Final = bytes([0x41, 0x54, 0x0D, 0x0A])  # AT\r\n from BLE module
+    TYPE_POS: Final[int] = 4  # frame type is right after the header
     INFO_LEN: Final[int] = 300
 
     def __init__(self, ble_device: BLEDevice, reconnect: bool = False) -> None:
@@ -45,7 +46,7 @@ def __init__(self, ble_device: BLEDevice, reconnect: bool = False) -> None:
         self._data: bytearray = bytearray()
         self._data_final: bytearray | None = None
         self._char_write_handle: int | None = None
-        self._valid_replies: list[int] = [0x2]
+        self._valid_replies: list[int] = [0x2]  # BMS ready confirmation
         self._FIELDS: Final[
             list[tuple[str, int, int, bool, Callable[[int], int | float]]]
         ] = [  # Protocol: JK02_32S; JK02_24S has offset -32
@@ -105,14 +106,15 @@ def _calc_values() -> set[str]:
     def _notification_handler(self, _sender, data: bytearray) -> None:
         """Retrieve BMS data update."""
 
-        if data[0 : len(self.BT_MODULE_MSG)] == self.BT_MODULE_MSG:
-            LOGGER.debug("(%s) filtering AT cmd", self._ble_device.name)
+        if data.startswith(self.BT_MODULE_MSG):
+            LOGGER.debug("(%s) filtering AT cmd", self.name)
             if len(data) == len(self.BT_MODULE_MSG):
                 return
             data = data[len(self.BT_MODULE_MSG) :]
 
         if (
-            len(self._data) >= self.INFO_LEN and data.startswith(self.HEAD_RSP)
+            len(self._data) >= self.INFO_LEN
+            and (data.startswith(self.HEAD_RSP) or data.startswith(self.HEAD_CMD))
         ) or not self._data.startswith(self.HEAD_RSP):
             self._data = bytearray()
 
@@ -120,32 +122,45 @@ def _notification_handler(self, _sender, data: bytearray) -> None:
 
         LOGGER.debug(
             "(%s) Rx BLE data (%s): %s",
-            self._ble_device.name,
+            self.name,
             "start" if data == self._data else "cnt.",
             data,
         )
 
-        # verify that data long enough and if answer is cell info (0x2)
-        if len(self._data) < self.INFO_LEN:
+        # verify that data long enough
+        if (
+            len(self._data) < self.INFO_LEN and self._data.startswith(self.HEAD_RSP)
+        ) or len(self._data) < self.TYPE_POS:
             return
 
-        if self._data[4] not in self._valid_replies:
+        # check that message type is expected
+        if self._data[self.TYPE_POS] not in self._valid_replies:
             LOGGER.debug(
-                "(%s) wrong message type %i (length %i): %s",
+                "(%s) unexpected message type 0x%x (length %i): %s",
                 self.name,
-                self._data[4],
+                self._data[self.TYPE_POS],
                 len(self._data),
                 self._data,
             )
             return
 
-        crc = self._crc(self._data[0 : self.INFO_LEN - 1])
-        if self._data[self.INFO_LEN - 1] != crc:
+        # trim message in case oversized
+        if len(self._data) > self.INFO_LEN:
+            LOGGER.debug(
+                "(%s) Wrong data length (%i): %s",
+                self.name,
+                len(self._data),
+                self._data,
+            )
+            self._data = self._data[: self.INFO_LEN]
+
+        crc = self._crc(self._data[:-1])
+        if self._data[-1] != crc:
             LOGGER.debug(
                 "(%s) Rx data CRC is invalid: %i != %i",
-                self._ble_device.name,
-                self._data[self.INFO_LEN - 1],
-                self._crc(self._data[0 : self.INFO_LEN - 1]),
+                self.name,
+                self._data[-1],
+                self._crc(self._data[:-1]),
             )
             self._data_final = None  # reset invalid data
         else:
@@ -161,7 +176,7 @@ async def _init_characteristics(self) -> None:
             for char in service.characteristics:
                 LOGGER.debug(
                     "(%s) Discovered %s (#%i): %s",
-                    self._ble_device.name,
+                    self.name,
                     char.uuid,
                     char.handle,
                     char.properties,
@@ -177,14 +192,14 @@ async def _init_characteristics(self) -> None:
                     ):
                         self._char_write_handle = char.handle
         if char_notify_handle is None or self._char_write_handle is None:
-            LOGGER.debug("(%s) Failed to detect characteristics", self._ble_device.name)
+            LOGGER.debug("(%s) Failed to detect characteristics", self.name)
             await self._client.disconnect()
             raise ConnectionError(
-                f"Failed to detect characteristics from {self._ble_device.name}."
+                f"Failed to detect characteristics from {self.name}."
             )
         LOGGER.debug(
             "(%s) Using characteristics handle #%i (notify), #%i (write)",
-            self._ble_device.name,
+            self.name,
             char_notify_handle,
             self._char_write_handle,
         )
@@ -192,13 +207,13 @@ async def _init_characteristics(self) -> None:
             char_notify_handle or 0, self._notification_handler
         )
 
-        # query device info frame (0x3)
-        self._valid_replies.append(0x3)
+        # query device info frame and wait for BMS ready (0xC8)
+        self._valid_replies.append(0xC8)
         await self._client.write_gatt_char(
             self._char_write_handle or 0, data=self._cmd(b"\x97")
         )
         await asyncio.wait_for(self._wait_event(), timeout=BAT_TIMEOUT)
-        self._valid_replies.remove(0x3)
+        self._valid_replies.remove(0xC8)
 
     def _crc(self, frame: bytes) -> int:
         """Calculate Jikong frame CRC."""
@@ -239,7 +254,7 @@ async def _async_update(self) -> BMSsample:
         """Update battery status information."""
         if not self._data_event.is_set():
             # request cell info (only if data is not constantly published)
-            LOGGER.debug("(%s) request cell info", self._ble_device.name)
+            LOGGER.debug("(%s) request cell info", self.name)
             await self._client.write_gatt_char(
                 self._char_write_handle or 0, data=self._cmd(b"\x96")
             )
@@ -248,14 +263,6 @@ async def _async_update(self) -> BMSsample:
         if self._data_final is None:
             return {}
 
-        if len(self._data_final) != self.INFO_LEN:
-            LOGGER.debug(
-                "(%s) Wrong data length (%i): %s",
-                self._ble_device.name,
-                len(self._data_final),
-                self._data_final,
-            )
-
         data = self._decode_data(self._data_final)
         data.update(self._cell_voltages(self._data_final, int(data[KEY_CELL_COUNT])))
 
diff --git a/tests/test_jikong_bms.py b/tests/test_jikong_bms.py
index 44e190a..ab38d15 100644
--- a/tests/test_jikong_bms.py
+++ b/tests/test_jikong_bms.py
@@ -22,14 +22,14 @@ class MockJikongBleakClient(MockBleakClient):
 
     HEAD_CMD = bytearray(b"\xAA\x55\x90\xEB")
     CMD_INFO = bytearray(b"\x96")
+    DEV_INFO = bytearray(b"\x97")
 
     def _response(
         self, char_specifier: BleakGATTCharacteristic | int | str | UUID, data: Buffer
     ) -> bytearray:
-        if (
-            char_specifier == 3
-            and bytearray(data)[0:5] == self.HEAD_CMD + self.CMD_INFO
-        ):
+        if char_specifier != 3:
+            return bytearray()
+        if bytearray(data)[0:5] == self.HEAD_CMD + self.CMD_INFO:
             return bytearray(
                 b"\x41\x54\x0d\x0a"  # added AT\r\n command
                 b"\x55\xaa\xeb\x90\x02\xc6\xc1\x0c\xc1\x0c\xc1\x0c\xc1\x0c\xc1\x0c\xc1\x0c"
@@ -50,6 +50,25 @@ def _response(
                 b"\x80\x51\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xfe"
                 b"\xff\x7f\xdc\x2f\x01\x01\xb0\x07\x00\x00\x00\xd0"
             )  # {"temperature": 18.4, "voltage": 52.234, "current": -10.595, "battery_level": 42, "cycle_charge": 117.575, "cycles": 2}
+        if bytearray(data)[0:5] == self.HEAD_CMD + self.DEV_INFO:
+            return bytearray(
+                b"\x55\xaa\xeb\x90\x03\xa3\x4a\x4b\x5f\x42\x32\x41\x38\x53\x32\x30\x50\x00\x00\x00"
+                b"\x00\x00\x31\x31\x2e\x58\x41\x00\x00\x00\x31\x31\x2e\x34\x38\x00\x00\x00\xe4\xa7"
+                b"\x46\x00\x07\x00\x00\x00\x31\x32\x76\x34\x32\x30\x61\x00\x00\x00\x00\x00\x00\x00"
+                b"\x00\x00\x31\x32\x33\x34\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x32\x34"
+                b"\x30\x37\x30\x34\x00\x00\x34\x30\x34\x30\x39\x32\x43\x32\x32\x36\x32\x00\x30\x30"
+                b"\x30\x00\x49\x6e\x70\x75\x74\x20\x55\x73\x65\x72\x64\x61\x74\x61\x00\x00\x31\x34"
+                b"\x30\x37\x30\x33\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+                b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xfe\xf9\xff\xff\x1f\x2d\x00\x02\x00\x00"
+                b"\x00\x00\x90\x1f\x00\x00\x00\x00\xc0\xd8\xe7\x32\x00\x00\x00\x01\x00\x00\x00\x00"
+                b"\x00\x00\x00\x00\x00\x00\x07\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+                b"\x00\x00\x41\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+                b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x09\x00\x00\x00\x64\x00"
+                b"\x00\x00\x5f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+                b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+                b"\x00\x00\x00\x00\x00\x00\x00\xfe\xbf\x21\x06\x00\x00\x00\x00\x00\x00\x00\x00\xd8"
+#                b"\xaa\x55\x90\xeb\xc8\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x44"
+            )  # Vendor_ID: JK_B2A8S20P, SN: 404092C2262, HW: V11.XA, SW: V11.48, power-on: 7, Version: 4.28.0
 
         return bytearray()
 
@@ -72,6 +91,8 @@ async def write_gatt_char(
             resp[i : i + BT_FRAME_SIZE] for i in range(0, len(resp), BT_FRAME_SIZE)
         ]:
             self._notify_callback("MockJikongBleakClient", notify_data)
+        if bytearray(data)[0:5] == self.HEAD_CMD + self.DEV_INFO:
+            self._notify_callback("MockJikongBleakClient", b"\xaa\x55\x90\xeb\xc8\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x44")
 
     class JKservice(BleakGATTService):
         """Mock the main battery info service from JiKong BMS."""
@@ -174,7 +195,7 @@ def characteristics(self) -> list[BleakGATTCharacteristic]:
             return [
                 self.CharNotify(None, lambda: 350),
                 self.CharWrite(None, lambda: 350),
-                self.CharFaulty(None, lambda: 350), # leave last!
+                self.CharFaulty(None, lambda: 350),  # leave last!
             ]
 
         def add_characteristic(self, characteristic: BleakGATTCharacteristic) -> None:
@@ -207,13 +228,13 @@ def services(self) -> BleakGATTServiceCollection:
 class MockInvalidBleakClient(MockJikongBleakClient):
     """Emulate a Jikong BMS BleakClient returning wrong data."""
 
-    def _response(
-        self, char_specifier: BleakGATTCharacteristic | int | str | UUID, data: Buffer
-    ) -> bytearray:
-        if char_specifier == 3:
-            return bytearray(b"\x55\xaa\xeb\x90\x02") + bytearray(295)
+    # def _response(
+    #     self, char_specifier: BleakGATTCharacteristic | int | str | UUID, data: Buffer
+    # ) -> bytearray:
+    #     if char_specifier == 3:
+    #         return bytearray(b"\x55\xaa\xeb\x90\x02") + bytearray(295)
 
-        return bytearray()
+    #     return bytearray()
 
     async def disconnect(self) -> bool:
         """Mock disconnect to raise BleakError."""
@@ -303,7 +324,7 @@ async def test_update(monkeypatch, reconnect_fixture) -> None:
         "temp#1": 18.1,
         "temp#2": 18.2,
         "temp#3": 18.0,
-        "temp#4": 18.3,     
+        "temp#4": 18.3,
     }
 
     # query again to check already connected state
@@ -315,9 +336,27 @@ async def test_update(monkeypatch, reconnect_fixture) -> None:
     await bms.disconnect()
 
 
+# @pytest.fixture(
+#     name="wrong_response",
+#     params=[
+#         bytearray(b"\x55\xaa\xeb\x90\x02") + bytearray(295), # incorrect CRC
+#         bytearray(b"\x55\xaa\xeb\x90\x05") + bytearray(295), # invalid frame type (0x5)
+#     ],
+# )
+# def response(request):
+#     """Return all possible BMS variants."""
+#     return request.param
+
+
 async def test_invalid_response(monkeypatch) -> None:
     """Test data update with BMS returning invalid data."""
 
+    monkeypatch.setattr(
+        "tests.test_jikong_bms.MockInvalidBleakClient._response",
+        lambda _s, _c_, d: bytearray(b"\x55\xaa\xeb\x90\x02")
+        + bytearray(295),  # incorrect CRC,
+    )
+
     monkeypatch.setattr(
         "custom_components.bms_ble.plugins.basebms.BleakClient",
         MockInvalidBleakClient,
@@ -332,6 +371,35 @@ async def test_invalid_response(monkeypatch) -> None:
     await bms.disconnect()
 
 
+async def test_invalid_frame_type(monkeypatch) -> None:
+    """Test data update with BMS returning invalid data."""
+
+    monkeypatch.setattr(
+        "custom_components.bms_ble.plugins.jikong_bms.BAT_TIMEOUT",
+        0.1,
+    )
+
+    monkeypatch.setattr(
+        "tests.test_jikong_bms.MockInvalidBleakClient._response",
+        lambda _s, _c_, d: bytearray(b"\x55\xaa\xeb\x90\x05")
+        + bytearray(295),  # invalid frame type (0x5)
+    )
+
+    monkeypatch.setattr(
+        "custom_components.bms_ble.plugins.basebms.BleakClient",
+        MockInvalidBleakClient,
+    )
+
+    bms = BMS(generate_ble_device("cc:cc:cc:cc:cc:cc", "MockBLEdevice", None, -73))
+
+    result = {}
+    with pytest.raises(TimeoutError):
+        result = await bms.async_update()
+    assert result == {}
+
+    await bms.disconnect()
+
+
 async def test_oversized_response(monkeypatch) -> None:
     """Test data update with BMS returning oversized data, result shall still be ok."""
 
@@ -377,7 +445,7 @@ async def test_oversized_response(monkeypatch) -> None:
         "temp#1": 18.1,
         "temp#2": 18.2,
         "temp#3": 18.0,
-        "temp#4": 18.3,        
+        "temp#4": 18.3,
     }
 
     await bms.disconnect()