hey this may contradict a few things but the battery would not cause the car to die( cell dead or no cell dead)
not start ,yes .
but die no as you can remove a battery from a running car and it will work as if nothing is wrong
the battery is only for starting and power to the car when the engine is off
i would say it was the alternator that was the problem in the first place and the load from a bad battery was causing the car to shut down when you pressed the brake to shift
since the alternaotr is already struggling to charge a bad batteryalso a loose connection at the battery