Accumulator

Accumulator is an additional energy reserve that your robot uses to power modules and equipments that require a quick burst of power.

All robots have an internal reactor, and that reactor provides the RP units (overall known as a powergrid") for fitting purposes. Modules that are fitted to the robot will be connected to the powergrid and reserve a portion of power for it's use (so that's why you have less RP to use after fitting a module). Such module will operate using just the power the reactor generates. But that wouldn't be enough for stuff like weapons, shield or miners and such.

So to fix that, Accumulator is used to apply excessive energy for more active modules, such as weapons. When needed, the Accumulator discharges required energy. It's reload mechanism is based on Gauss curve, where at 0% and 100% it recharge tempo is the slowest, and around 50% - the fastest.