my laptop suddenly doesnt liek sims 3 anymore

i have never had a problem playing sims 3 before on my laptop.but in the last couple days,when i start my sims 3 game,my screen dims and brightens back up like a blinker,and i notice when it does that,my charging battery light comes on,and the power icon in my sys tray goes from being plugged in,to running on battery,it does it in unison with my screen blinking.i only get this with sims 3.anyone else ever had this issue???