Does my adrenaline shot always start at 20% and can it go higher?

I have used this shot through the entire game and it always in the heat of battle only comes up to 20% ugh! :flushed: Would be sweet if it could go higher or even 100%! Can it, and how do i make this happen if it"s possible?

Its always 20% unless you get the specialisation β€˜Medic’ in which case itll always be 100% unless you equip a different specialisation.