My Xbox controller keeps turning off?

randomly whenever both my controllers because me n my brother are both playin, my controllers just start blinking around them middle and on the tv it says that our controllers are discounected and its not the batteries cuz i just put a fresh pack in, and its not cuz we're sittin to far away cuz we're right up front of the screen. i dont kno y but it dosnt stop doing this all the time. the past 10 minutes from rite now its done that 5 times after turning it on then off and restarting it again. i really need to kno.