It could be an alternator. Check with a mechanic if that is the issue.
The battery needs to be replaced
It uses voltage from the alternator which in-turns comes from the battery.......
did you check the alternator??
Inside the alternator
The battery in the remote needs to be replaced.
Voltage regulator or loose wire.
Check the battery cables or starter.
Not charging. Poor battery, poor alternator, voltage regulator, slipping drive belt.
Alternator is not charging. Have it tested and/or replaced.
Battery light usually means alternator not charging. Most common solutions would be be a bad alternator, bad connection, or loose alt belt.
The same thing happened to my 1992 Corolla, and it means the alternator needs to be replaced. Although the same thing happened again when the belt went out on my water pump.