It uses a charge for Nightstalker, as you must activate an upgrade node to have the secondary grenade turn you and allies invisible. As for Bladedancer, you can turn invisible one of three ways. You must stay crouched without moving for some seconds (which is not convenient in the middle of battle, and you have to have the upgrade node activated), you can activate an upgrade node to have your blink strike turn you invisible which does end up using a melee charge. Or you can activate a node to have it so when you pop your super, you turn Invisible, and whenever you pull the trigger you go invisible (it uses super energy for that). So only one method out of four does not use some sort of charge, be it melee or super energy. However, the crouch invisibility is not an instant activation like the other three methods. And does require the user to stay still while crouched without getting shot or shooting at anything for a few seconds. You should also listen for the audio cue, or keep your eyes open as it is pretty easy to notice if you know what you are looking for. May be b8, but I like to explain it anyway.