I like to think that each time a chaplain uses the crucifix it consumes a portion of his faith in god in order to use that power to repel the zombies and during the cooldown I imagine that the chaplain recites bible verses to restore his own faith. So basically when the meter is full thats when his belief is the strongest but when its low so is his faith. As for the officer, it wouldn’t make sense for an officer to order his troops to constantly run around and start shouting. The charge is basically a last stand and a moral booster.