poor charge or intermitant charge from the alternator, also check condition of the alternator belt
Battery light usually means alternator not charging. Most common solutions would be be a bad alternator, bad connection, or loose alt belt.
Possible alternator problem
More than likely your alternator is getting ready to go out.
Loose connection? Bad ground? Weak battery?
Normally it means the alternator is failing.
It is possibley your alternator or battery
Sounds like the brushes are worn down in the alternator.
If the battery light flickers, it's losing voltage. It would be worse when the lights and other accessories are running. It just may not be enough to kill it yet. I would suspect parts in this order. Alternator(if there is a voltage guage, should be around 13-14 volts) discharged battery
Probably your battery cable or cables are loose on one end or the other.
Keep the car light on
The car light? YES! Leaving your car light on WILL make your battery run out. Things like leaving your car door open if the light is on because it is open will cause the lgiht to Mae your car battery run out. There is a big difference between shorted out a car battery and running the battery down. Lighting in itself won't short a battery out but will run it down.
the battery light means that your battery is being charged properly. so let it light.