Why does my BMW 2 Series battery keep dying even after replacing the alternator?

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Why does my BMW 2 Series battery keep dying even after replacing the alternator?

I recently replaced my BMW 2 Series alternator because the battery wasn’t charging properly. However, I’m still facing the same issue. Could there be another underlying problem causing alternator failure, and what should I check next?

Garitips asked on 19 Feb 2025 13:30:37 pm

1 Answer

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Garitips - on 19 Feb 2025 14:08:40 pm

If your battery still drains after replacing the alternator, consider these possible causes:

Faulty Battery: Even if the alternator is working fine, an old o r weak battery may not hold a charge properly.
Bad Wiring o r Loose Connections: Corroded o r loose connections between the alternator, battery, and grounding points can prevent proper charging.
Parasitic Drain: Some electronic components like aftermarket accessories, alarms, o r faulty modules may be draining the battery when the car is off.
Defective Voltage Regulator: If the new alternator’s voltage regulator is faulty, it may not charge the battery correctly.
Solution:

Get a battery load test to check if the battery is still good.
Inspect and tighten all electrical connections.
Use a multimeter to check for parasitic drain a draw higher than 50mA when the car is off is a concern.
Ensure the alternator voltage regulator is functioning properly.