Insert a flat-head screwdriver into the small opening located on the bottom of the unit. This opening is just above the jack where you would normally insert the power cable for recharging. According to Black and Decker, there is a small tab inside this opening.
Press the tab with your screwdriver until the bottom part of the hand vac's casing pops off.
Grasp the battery pull tab near the top of the battery compartment.
Pull the tab toward you until the battery pops out. The batteries will be inside a plastic casing. Do not remove this plastic, as it is designed to protect you from any possible battery leakage.
Insert a new battery pack into the battery compartment.
Snap the plastic casing back on top of the battery compartment.
Dispose of the old battery at a recycling center. You may also be able to drop the battery off at an electronics store that participates in a battery recycling program. Black and Decker recommends calling 1-800-8BATTERY to find participating facilities in your area.