I am running the evic vtc mini with cubis tank and an LG 18650 battery. Bought it two weeks ago and was working amazing. Then one day it started saying low battery but behaving as the manual says a weak battery should supposed to (making you lower the wattage to run). All while showing an almost full battery. Problems seemed to go away. Went to sleep with the battery icon full. Woke up with a black screen. Wouldnt charge. Took it in. Guy said battery extremely low. Bought new battery. No matter how much I hit it battery not showing drainage. What's going on here? Thanks so much in advance.