To replace the battery on your O2EII Pro

  1. Unscrew the 4 slot screws on the sensor face of the unit
  2. Remove the sensor face
  3. Disconnect the plug from the battery
  4. Connect the battery plug to the new battery (will only fit one way)
  5. Refit the battery
  6. Refit the sensor face (being careful not to pinch the wires between the faces of the device)
  7. Fasten the 4 slot screws in the sensor face of the unit