Defibtech Lifeline 5-years battery.
Defibtech's battery technology is nothing short of brilliant! A replaceable 9 volt battery powers the device's regular electronic self-tests leaving the pack available for any emergency use. This "high-use" pack offers up to five years of standby life. It's another great innovation from Defibtech. If you don't need a high-use battery. The Defibtech AED defibrillators function on batteries only.
Always have a fully charged spare.