Power Up Arduino Uno Using Battery

The video shows how to make up a cable to connect a 9V battery to an Arduino Uno.
A 2.1mm barrel connector is soldered to a battery clip with the positive (red) wire connected to the centre of the barrel connector.
The pre-loaded blink program starts working, when connected or powered up!

The voltage of the battery will be about 9V if six 1.5V cells are used in the battery holder. If rechargeable cells are used, the battery will produce about 7.2V.
Powering an Arduino Uno from a 9V battery