Hi CEEFBEE -
If you know your battery is bad, only an Xfinity Home technician can replace it. Please give us a call and we can schedule an appointment for a technician to come by to install the battery and make sure everything looks good afterward.
Note - some people feel they need a new battery because the Touchscreen's display goes dark during a power loss. This is normal, and is done to conserve battery power. Tapping on the Touchscreen will temporarily cause it to light back up during a power loss.
Also, cameras will not function during a power loss, as they require electricity to work. Life-safety features such as Motion Dectection and Door & Window sensors will still work, and any alarms will still be transmissed to the Central Monitoring station via Cellular Backup, assuming your Internet Connection is down as well.