Check for a battery warning light on the dashboard
Measure battery voltage with the engine off
Measure battery voltage with the engine running
Look for dim or flickering headlights
Test for slow or weak electrical accessories
Listen for whining, grinding, or squealing noises from the alternator
Inspect the alternator belt for looseness, wear, or damage
Check for corroded or loose battery and alternator connections
Test the alternator output with a multimeter
Have the charging system tested at an auto parts store or repair shop