The main culprits of that light are:
NEVER THE BATTERY.. that light has nothing to do with the battery.
MEGA-FUSE, but would cause the light to be on ALL THE TIME.
Alternator (voltage regulator is on the alternator, and replacing the VR requires ALMOST ASSUREDLY) removing the alternator either way).
Wiring from alternator to chassis, or battery. usually accompanied by flickering interior/exterior lighting.
Car off, 60 secs of headlights on to remove surface charge:
12.0v or higher
car running:
14.0 or close. (up to 14.7ish) some as low as 13.9/8ish
If not higher than the 12, replace the alternator, using the how-to, or pay for it to be done 9but be ready to pay heavily)
