why does the battery die in my BMW 5 Series F10/F11 (2010-2017) when parked

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, and cleaning materials for battery terminals.
• Ensure the vehicle is parked on a flat surface and the engine is off.
• Disconnect the negative battery terminal to ensure safety during inspection.

2. Inspect the Battery

• Remove the battery from the vehicle if corrosion is present.
• Clean the terminals with a mixture of baking soda and water to neutralize acid.
• Inspect the battery label for the manufacturing date; replace if older than 4-5 years.

3. Address Parasitic Draw

• Reconnect the negative battery terminal and set up the multimeter to measure current draw.
• Identify any components drawing excessive current (over 50 mA) when the vehicle is off.
• Disconnect suspected components one at a time until the draw drops to an acceptable level.

4. Check Alternator Function

• Reconnect battery and start the engine.
• Use the multimeter to measure voltage at the battery terminals; it should read between 13.8 and 14.5 volts when running, indicating proper charging.
• If the output is insufficient, inspect the alternator belt for wear and ensure it is properly tensioned.

5. Replace Components if Necessary

• If the battery or alternator is faulty, replace with OEM parts.
• Ensure all connectors are tight and free from corrosion.