This battery is necessary for the AED to perform self-tests, and is used to power the Active Status Indicator. This 9V lithium battery is included with the purchase of a Defibtech Lifeline 5-Year Battery DCF-200 or Defibtech Lifeline 7-Year Battery DCF-210 replacement battery for the Defibtech Lifeline AED. 

The 9-volt battery is inserted into the battery pack. Battery life is approximately one year when installed in the AED.