Samsung Note 4, roughly 16 months old. So, I've been having this problem for a while, I'll charge my phone to full, unplug it and start using it, then it'll die anywhere between 20%-60%. It doesn't do this all the time, it's very random. I decided to try getting a new battery, I bought a genuine Samsung battery, as didn't want to get a cheap replacement. Low and behold, it happened again last night. Went to bed full charge, unplugged it, went sleep. I awoke to a dead phone. So, does any one have any suggestions as to what I do? Is there anything I can do to fix this? Thanks.