The Chargepad is a wireless electric charging station. Any rechargeable items you have in your inventory will be charged while standing on it.
The Chargepad can recharge any item that requires any form of energy. A few examples are RF based tools like those from Tinkers' Construct (if they are equipped with Flux modifiers), Applied Energistics' ME Wireless Access Terminal, and some Modular Power Suits. It also functions as the deployment and teleportation point for your Robit.
The Chargepad requires a source of power to function, which can only be supplied through the bottom of the pad via any compatible cable.