How to replace your Physio-control Lifepak CR2 battery: 1. Place the device face down to reveal the back of the AED 2. Locate the battery compartment and remove battery 3. Push new CR2 lithium battery into compartment until you hear a click 4. Verify the Rescue Indicator on the front of the device is flashing green - you can find this in the center top of the device above the heart