Probably have a 'parasitic load'. This is something causing an abnormal battery drain while the car is off.
usualy if the alternator is not defective then its the battery. you should start by cleaning the battery post. then you could check the terminal wire that runs from the battery post to the alternator. if thats not it you should check the ground on the alternator.
its the alternator if the car is running with a battery light on. but check fuses first
Possibly a wiring issue. Check the harness and connector at the alternator for corrosion and make sure they are properly attached. Check the battery cables for corrosion also. Lastly, check the main fuses (the big ones under the hood - about 6 of them). If all this is fine, take it to a good shop.
Simple, have the alternator checked and if it is okay, check the alternator circuit to the battery
If the alternator is not working the battery gets discharged. In most cars a light will show on the dashboard - battery light icon, and this will suggest fault in the battery or alternator. You will need to start the car and check if it is charging the battery, and most garages will do this check for you
check the alternator. Use a digital multimeter and with engine running you should have 13-14 volts at the battery. If less than 12.5 Alternator is not charging Also check the amperage the alternator is putting out.
check your battery ground and your alternator ground
Usually when the battery light comes on its the Alternator, or a bad wire from Alternator to battery, but id check Alternator first.
Is the battery dead? Check for 12v on the main alternator cable. If no power, check for burned out fusible links between alternator and battery. You may need a wiring diagram to check further.
Check battery connections, check alternator out put. Exc.
Check your battery for loose connections and check your alternator.
did you check the alternator??