Dash Battery Light

2001 330ci cabrio with 12,000 miles. Batttery light stays on. Manual says it could be several things. What's the best way to determine the true fault?
Thank You RC
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If the car is less than 48 months old, the best way is to let the dealer fix it under warranty. Out of warranty DIY, get out your DMM (digital multi meter) and test the battery voltage with car on and also off. With the car on (engine running) you should get around 13.5-13.7v at the battery. Less than this usually indicates a bad alternator. A good reading with the car running and a low one (12.5v or less) with the car off usually indicates a dead battery.
Kyle. 98 740iL 97 M3
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