The PA-BB-002 battery base unit is a user installable accessory that is
required for using the Lithium ion rechargeable battery (PA-BT4000LI)
option. This battery base unit is easily assembled to the bottom of a
Brother PT-P900W or PT-P950NW printer. When installed, the printer with
battery configuration will have the same size footprint of just the
printer but the height will increase to about 8-3/4”. Just remove the
bottom cover from the printer, plug in the power connector, position the
battery base and attach it to the printer with the supplied screws.