Does it have a battery?

No. The ticker is built to run all day and all night, with its screen on and its prices fresh, and that is not a job for a battery. It draws about one watt from any USB port or the adapter in the box.

Unplugging it loses nothing. When the power comes back it starts up, rejoins your Wi-Fi and carries on with the same coins and settings. See After a power cut.

Where there is Wi-Fi but no outlet, a USB power bank runs it. Some power banks switch themselves off when the device on them draws very little, and the ticker draws very little, so a bank that stays on for small devices works best. See Power and the USB cable.