Backup Battery

Hi , my Arduino powered by 12V DC support a motor . I want to use a backup battery so that it could continue even if the powered is turned off . Is it applicable ? please help .

You're better off powering the Arduino separately in the first place, then
you won't risk noise/spikes on the 12V motor supply trashing / reseting the
Arduino.

A 7.2V pack into Vin is one way, a USB 5V supply into the USB jack is another
(though those tend to be main powered).

Why will turn the power off when it needs to be on?

If you are thinking of interruptions to mains electricity a simple solution would be to power the Arduino from a battery that is normally kept at full charge by a mains charger. In practice the mains charger will be powering the Arduino until the mains supply fails and then the battery will take over seamlessly.

...R