Charging doorbell

No charger was included because it is designed to be wired into your existing mechanical door.  Others have posted they have acquired a power converter and connected the doorbell through a hole in the wall, assuming power receptacle within reach of the door bell.

If you wired your SS Doorbell to your existing doorbell wiring, the small amount of voltage that the old doorbell used to make the connection and ring will keep your SS Doorbell charged.  This is all based on whether I read the documentation correctly.

Since installing the Doorbell Pro, January 20, 2020. I have had to recharge its battery twice using a USB connection. The door bell was connected to the existing doorbell wiring, when tested it rang the chime in the house. I assumed the wiring had some voltage in it to make the door chime ring. Questions:
1. is it correct to assume the existing wiring has sufficient voltage in it to charge the battery (it doesn't that I can see or the battery wouldn't run down in the first place).
2. How long should the charge on the battery last IF the voltage doesn't keep it charged up.
3. How long should it take to charge the battery using usb connection.

Thanks