Batteries can either be used to craft tools and pieces of equipment or to refill their energy. Batteries can be swapped out or removed from tools regardless of how much energy is left.
The Battery can also be charged in the Battery Charger or with Swim Charge Fins (for equipped tools only). This allows the player to recharge their tools without having to craft new batteries constantly.
There is an upgraded version of this power source, called the the Ion Battery.