The pak has 2 sets of electrodes. The Physio-Control Lifepak CR Plus Charge Pak is usable for the Lifepak CR Plus and Lifepak Express.
It is recommended that after each use of the CRplus with a shock is to replace the battery. The battery has enough power for 30x (360 Joules) defibrillations. The current sets have a shelf life of approximately 2.5 years instead of 2 years!