i had the same problem! replaced my alternator 3 times! battery light kept coming on, finally took it to an alternator specialist, come to find out my wireing was connected wrong, and the connector was bad, car wasn't reading the alternator correctly causing the alternator to shut down. Got it fixed for roughly 350 dollars but no problems since, suggest brand new alternator not a rebuilt one!
the battery could have a dead cell, this could cause it to not charge. Have the battery tested to be sure.
Have the alternator checked.
Loose alternator drive belt or loose or corroded battery cables. The battery itself may also be bad.
Its a sign that either your battery or alternator is starting to fail.
The most probable cause is a bad connection somewhere in the alternator > battery circuit. Check if the alternator is operational. Clean all contacts with a steel brush.
Battery light usually means alternator not charging. Most common solutions would be be a bad alternator, bad connection, or loose alternator belt. If the battery and alt test ok than check the connections to the alternator and battery. The alternator should have 2 connections.
The ground cable, on the battery may need to be tightened or cleaned. The alternator voltage regulator may need to be replaced.
One possible cause is a defective alternator, Have the charging system checked.
If your battery is not fully functioning and needs to be replaced, it can make the alternator work harder. This could cause a brand new alternator to go bad. Check your battery, if the battery is not the issue, return the alternator, it should have a warranty on it for at least the first 30 days.
The PLIP battery on the Peugeot 307 means that the battery is in need of charging. It can also mean there is a problem with the battery cables or the battery needs to be replaced. Not replacing the battery when necessary can also cause problems for the alternator.
Check for a key off draw (or parasitic draw) Should be less than .5 Amps
Have you had the alternator tested? Often a bad internal diode can drain the alternator overnight.