You just said the same thing I did when you typed this...... but I like redundancies today.
" stores the energy in a battery pack" That is taking the mechanical energy which is turned into electrical energy to give a boost on a lap.
People said that laser discs were a way of the future and look at those. Same goes for eight tracks for all you "old heads" out there.
edit: I bet Full EV's will be out and about before this is ever put down on a production, consumer, and/or massive level. Or I may be dead and buried by the time this takes off. Who really knows?