I have an itaste vv 3.0, mvp 2.0, and vamo 2 and vamo 5. I don't quite know what the heck is going on since the vamos use external batteries but none of my devices stay charged now for more than 2 hours. Can anyone recommend anything new that might be different? I hate that nothing will stay charged. Clearly for the vamos I need to buy new batteries but just wondering about the other things that have installed batteries. Nothing is more annoying than fully charging something that dies 2 hours later with little use.