PHYSIO LP500 Non-Rechargeable Lithium Sulfer Dioxide Battery Pak – This battery is a long-life low-maintenance battery pack. It is designed for low or infrequent use environments. The lithium battery pack requires less maintenance than the SLA battery pack since it never requires recharging. Battery discharger included. This battery is design to automatically turn off the AED of the if it’s not connected to a patient and no buttons are pressed. It can last up to 4 years in the LifePak without having to be recharged. It is advised that you keep a spare battery on hand in case one is needed.