Aluminum AirTag case replaces coin cell with 2 AA Lithium batteries for extended lifespan. ... a new $20 battery case purported to extend Apple AirTag battery life from one year to 10 years.

If you figure the average AA battery is 1.2 volts, then it's okay to assume the Xbox Core controller requires a minimum of 2.4 volts, giving an average of 2,100mAh per battery pack in this kit.