Can i always count on getting nine hours of continuous battery operation on fully-charged battery?
Updated
Age of battery pack. The battery pack will lose some charge capacity over time.
Use of the backlight display function. This option discharges the battery pack faster.
Operating the unit at the upper end of the specified operating temperature range, causing the internal fan to power on more often. This may especially be observed with multiple, rapid, high-energy defibrillator pulse discharges into the unit.