04 ford ranger battery light when I rev the engine high

i have an 04 ford ranger, 70k mi, 4 cyl 5speed manual, great lil truck in excellent condition, really goes! when I am starting from a stop with the clutch in and i rev the motor excessively high, my battery light comes on on my insturment panel. is this a sign of a bad battery? belt? alternator? thanks! input welcome.

could be a loose alternator belt?

Confirm the tension on the serpentine belt, then get the charging system checked. If the belt is OK, the alternator is next suspect.