what should I do if my BMW 3 Series G20/G21 (2019-2024) battery dies repeatedly?

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, basic hand tools (socket set, wrenches), battery terminal cleaner.
• Ensure the vehicle is parked on a flat surface and the ignition is off before starting work.

2. Replace the Battery

• Sub-steps:
  1. Disconnect the negative terminal first, followed by the positive terminal.
  2. Remove any securing brackets or covers that hold the battery in place.
  3. Carefully lift the old battery out of the vehicle.
  4. Clean the battery tray and terminals with a battery terminal cleaner.
  5. Install the new battery in reverse order: place it in the tray, secure it with brackets, and connect the positive terminal first, then the negative terminal.

3. Test and Replace Alternator (if necessary)

• Sub-steps:
  1. Disconnect the battery again to work safely on the alternator.
  2. Remove the serpentine belt by releasing tension from the belt tensioner.
  3. Unplug the electrical connectors from the alternator and remove any securing bolts.
  4. Replace the alternator with a new unit, reattach all connectors and bolts, and reinstall the serpentine belt.
  5. Reconnect the battery terminals.

4. Address Electrical Issues

• Sub-steps:
  1. Inspect and replace any faulty fuses or problematic relays identified during diagnostics.
  2. If excessive draw was detected, identify and repair any short circuits or malfunctioning accessories.
  3. Use the multimeter to ensure that the current draw is now within the acceptable range.