Powered
A melee weapon with an internal battery that must be charged to function has the powered special property, which lists its capacity and usage. Unlike with a ranged weapon, the usage is for 1 minute of operation rather than per attack, though using a powered weapon for less than 1 full minute still expends 1 full usage. The number of charges expended is equal to the usage × the number of minutes the weapon is used, rounded up to the nearest minute. You can activate the power of the weapon as part of the action used to make an attack with it, and it automatically deactivates after 1 minute. As with ranged weapons, you can recharge the battery of a powered melee weapon using a generator or a recharging station, or you can purchase new batteries for it. If you try to attack with a powered weapon that’s out of charges, it functions as an improvised weapon (see page 169).
Source
Core Rulebook pg. 181