The battery warning light illuminates when the battery isn't being charged , get it checked out to find the problem and then repair.
Reset the battery
There is no reset for the battery (charging system) warning light. It is on because there is a problem. Once you repair the problem the light will go out. More than likely the alternator has failed.
The check engine and other dash warning lights can be reset by disconnecting the vehicles battery for more then 5 minutes. If warning light continues after reconnecting battery then there is still a problem.
Should be able to reset it by disconnecting the negative battery cable from the battery for ten minutes.
Remove battery cable for one minute .
Disconnect the negative battery cable for 30 minutes.
try disconnecting the battery for a minute.
To reset the maintenance required warning light on a 1989 Dodge Dakota, unhook the battery connector cables for 10 minutes. Reconnect them and start the vehicle.
If you undo the negative (Black) lead from the battery terminal and leave the car for 15 mins then put it back. This should reset the memory clearing the warning light. Regards James
Disconnect the battery for 15 mins
The charging warning light should automatically reset if the battery is disconnected. Check the battery cables and ensure they are properly connected. Also check the alternator connections. If the light is still on there may be a problem with the new alternator.
Remove the negative battery cable fromthe battery and let it set for about 30 minutes.