Check the fuses, they could be fried.
the battery
did you unhook the battery before replacing the alternator
my battery is still on after changing battery and altnator
You might have a bad battery, a poor connection between the battery and alternator, or a bad ground from the battery.
Alternator is defective and needs replacing.
The alternator is probably bad. That is what recharges your battery
Battery may have a dead cell and need replacing.
The vehicle should ave a voltage regulator. If the battery and alternator are good then the regulator is most likely bad.
With the car or truck running disconnect only the positive side of the battery ... if it stays running that means the alternator is good if it dies then it needs replacing
You need to replaced the starter or the alternator.
If the light is still on then the problem was not the battery but was instead the alternator which is more than likely defective.
If the alternator is not producing 13.5 to 15.5 volts it is defective and needs replacing.