This disclosure describes methods and apparatus for indicating battery cell status on a battery pack assembly used during mechanical ventilation. Embodiments described herein seek to provide methods for indicating battery cell status on the exposed exterior of a battery assembly pack both when the battery is in use and when the battery is not in use during mechanical ventilation. Embodiments utilize power from the ventilator as well as power from the battery pack itself to light the indicators during periods of battery use and non-use, respectively. Embodiments described herein further seek to provide an apparatus indicating battery cell status on the exposed exterior of the battery pack assembly during mechanical ventilation. Embodiments described herein further seek to provide an apparatus for a battery pack assembly used during mechanical ventilation. Embodiments described herein seek to provide a system for a ventilation system with an inserted battery pack assembly.