why does my Volkswagen Passat B8 (2015-2022) battery die overnight when parked

Solution

1. Preparation

• Tools Required: Multimeter, socket set, wire brush, battery terminal cleaner, safety gloves.
• Disconnect the negative battery terminal to prevent any shocks or short circuits.

2. Clean Battery Terminals

• Sub-steps:
  1. Use a wire brush and battery terminal cleaner to remove any corrosion from the battery terminals.
  2. Reconnect the battery terminals securely, ensuring a tight connection.

3. Address Parasitic Draw

• Sub-steps:
  1. After performing the parasitic draw test, identify the component causing excessive draw.
  2. Repair or replace the faulty component (e.g., trunk light switch, aftermarket accessory).
  3. If the draw is within acceptable limits, reconnect the battery.

4. Test and Replace Battery (if necessary)

• Sub-steps:
  1. If the battery voltage is low (below 12.4 volts) and unable to hold a charge, consider replacing the battery.
  2. Choose a battery compatible with the Volkswagen Passat B8 specifications (e.g., Group 48).
  3. Install the new battery and ensure all connections are tight.

5. Check Charging System

• Sub-steps:
  1. After starting the vehicle, use the multimeter to measure alternator output.
  2. If the output is below 13.7 volts, inspect the alternator and replace if necessary.