The next part of your drone is your esc battery. Modern RC drones use lipo batteries, which have a good power to weight ratio and can discharge a large amount of current very quickly.
Physical Size of TTF Longest Lasting Drone Battery
When your model is equipped with an enclosed diy drone battery compartment shrink-wrapped are ok too.

Shenzhen TitanFlying Technology Co., Ltd is a high-tech enterprise and professional Aero-Model manufacturer that unifies product design, research development, production, marketing and customer service. Our main product are uamanned aerial vehicle, including professional drones and consumer drones, as well as DIY components for drones.