Tracer Battery Light On When Press on Gas Pedal

Hi, I want to thank anyone who reads this and helps me to diagnose this problem my car is having.

Last night on my way home the battery light was blinking on and off but would come on when I pressed on the gas pedal.

My father in law is wondering if it is the alternator possibly? He can change it if it is but he wasn't sure so I thought I would ask and one of you car guru's can help me out.

Thanks much!
January