Battery light usually means alternator not charging. Most common solutions would be be a bad alternator, bad connection, or loose alternator belt. If the battery and alt test ok than check the connections to the alternator and battery.
It is usually caused by a bad alternator.
It's most likely your alternator going out, or something wrong with the charging system.....
underneath the alternator battery
weak battery or bad alternator.
Check a for a blown/burned out fuseable link between starter and alternator
Your alternator is defective. Could be the internal voltage regulator or one or more bad diodes. Replace as soon as you can to avoid getting stranded on the road.
Check alternator
Mine had an alternator problem not putting out 14 v
If the battey is dead it won't charge. But it sounds like the alternator is bad. If you're sure tha battery is good then it has to be alternator, wiring, connectors or switch.
alternator and od solonoid
It's not the battery you have to worry about it is the alternator. it should handle an average amp and sub woofer.
Remove the bolt retaining the heater hose clamp to the alternator adjusting bracketRemove the bolt retaining the negative battery cable to the alternator adjusting bracketif equipped if not remove the negative battery cableDisconnect the cable from the positive battery cableDisconnect the two electrical connectors from the rear of the alternatorRemove the bolt retaining the alternator to the adjusting bracketRemove the alternator pivot bolt and remove the alternator from the car