All of mine are prefilled and there's a vast difference between today's and a few months ago. I'm afraid to open a new carto for friends to try now because they just don't satisfy, they're like vaping on a flooded carto, they don't sizzle, they just suck lol. (I'm saving the last great pack for me). There is a difference I'm afraid. The last packs I've received have all been sucky. (vapable, yes, but not delightfully so). I won't return them, because I do use them, but just don't like them like the previous ones. I, too, thought it was my battery needing cleaning (although they do get cleaned every change out), but man oh man when I pulled out a Nov carto, I can assure you there is nothing wrong with the batteries. It's like the difference between a Volt PT and a BluPoo