This battery case holds 3 AA batteries and connect them in serial so that you can use as a portable power for your project.

It has an ON/OFF switch at the back and two unterminated wire come out of the box with the regular red wire for positive and black wire for negative. polarity

The batteries could add up to anything between 3.6V to 4.5V depending on which AA battery type that you use, alkalines or rechargables.