The batteries are not for IFE. One is for starting the APU (a generator that starts the main engines and supplies power on the ground), and the other is for supplying the critical systems when both engines and the APU fail simultaneously (i.e., they run out of gas).
When the engines are turning, there is no shortage of power for amenities.
They used LiIon batteries for the same reason your laptop and phone do: they're small and have good energy density. The older technologies are not. Weight is a big deal and when you want 10% better fuel economy than you had before, you need to cut every gram.
When the engines are turning, there is no shortage of power for amenities.
They used LiIon batteries for the same reason your laptop and phone do: they're small and have good energy density. The older technologies are not. Weight is a big deal and when you want 10% better fuel economy than you had before, you need to cut every gram.