1. Battery Fault: The new battery itself may be defective or damaged. Despite showing a charging status, it might have internal issues that prevent it from holding or releasing charge properly.
2. Charging System Issue: There might be a problem with the charging system in the car. This could be due to a faulty alternator, voltage regulator, wiring issues, or other electrical component malfunctions. Even though the battery shows to be charging, the problem may lie within the system's ability to maintain the charge.
3. Poor Electrical Connections: Check the battery terminals and connections to ensure they are clean, secure, and free of corrosion. Loose or corroded connections can affect the battery's ability to charge and discharge properly.
4. Parasitic Draw: There might be a parasitic draw or excessive power drain on the vehicle's electrical system. A faulty component, such as a light left on or a short circuit, could be draining the battery even while it's charging.
5. Temperature Sensitivity: Some batteries may be sensitive to temperature changes. Extreme cold or hot weather conditions can affect the battery's performance, making it difficult to disconnect or leading to inconsistent charging behavior.
6. ECU or Sensor Issue: In certain vehicles, the Engine Control Unit (ECU) or sensors might play a role in managing the charging system. A malfunction or glitch in these components could cause the battery to show charging but not allow disconnection.
To troubleshoot this issue accurately, it's recommended to have the vehicle diagnosed by a qualified mechanic or auto electrician who can assess the charging system and identify the root cause of the problem.
