More than likely your alternator is getting ready to go out.
Possible alternator problem
Loose connection? Bad ground? Weak battery?
Normally it means the alternator is failing.
Sounds like the brushes are worn down in the alternator.
Battery light usually means alternator not charging. Most common solutions would be be a bad alternator, bad connection, or loose alt belt.
poor charge or intermitant charge from the alternator, also check condition of the alternator belt
Probably your battery cable or cables are loose on one end or the other.
To flicker or shimmer erratically.
Light can flicker when there are fluctuations in the electrical current powering the light source, causing the intensity of the light to vary rapidly.
Clean both battery cables and check the connections on the alternator. If it continues, go to auto zone and have the alternator checked.
Fluorescent lights flicker because they rely on a ballast to regulate the flow of electricity. If the ballast is faulty or the light bulb is reaching the end of its lifespan, it can cause the light to flicker.
Having too much play in the emergency brake handle in the middle of the console could lead to the brake light flickering. At least this was true for me.