Use the Battery Recharging Blaster on enough Phase Hunters to get the Battery Recharge Level to 10. Then return it to Bot-Specialist Alley at the Ruins of Enkaat in the Netherstorm.
I have the very important task of collecting the machinery inside these ruins, but I'm having a problem keeping all of my bots charged up.
The phase hunters - those wyrm-looking things - have lots of energy! You can find them all over the edges of this island, floating in from the nether.
Fill the battery on this recharging blaster by using it on a phase hunter when they're very weak, and then finish it off to soak up the last of its energy.