[T-Mobile Galaxy Note 4 Q&A, Help & Troubleshooting] C-4Nati:
Ok, so I have had no issues at all since buying this phone at launch, and this randomly happened yesterday.

I was on my phone and checked the battery info as I do a few times a day, just to see what's using my battery the most, SoT, etc. I was at 87%, which was about right as it has been off the charger a few hours with some light use. A few hours later I noticed my actual battery icon was exactly the same, no drainage at all. I viewed my battery info, and the line was flat for a few hours and still said 87%, which is very inaccurate as I've been using it during those few hours. If I had to guess, I was realistically around 60-70%. Then, while looking at my battery info, it said 'battery critically low' and shut off. I plugged in the charger and the animation when the phone is off said 0%. I left it plugged in for like an hour, and turned it on and it still said 0%. I unplugged the charger and it immediately died. I was on pop rocks ROM when this happened. I then plugged it back in, because the phone would function as normal as long as the charger was plugged in. I booted into recovery and restored an old stock backup, even after that I'm having the same issue. I downloaded a stock ROM from here, wiped everything like normal, same issue. Here's the frustrating part -- I chalked it up to this battery being bad. But I have two batteries, and the other one I hardly ever use, but I've used it before and it was fine and normal. I put that battery in, I'm having the same stupid issue! I don't understand, no matter what ROM or batter I use, this is happening. This is so frustrating, I don't know what to do or why this is happening. The phone will not charge at all. Please, anyone I would greatly appreciate help. I searched for issues like this on Google and here but it's usually chalked up to a bad battery, but I know that's not the case here. I couldn't find the option in TWRP, so I downloaded 'battery calibrator' app and wiped my battery stats, still didn't help. Below is a link to picture of what it looks like when I charge it, it just stays like this. I've done it with fast charging on, off, and with the phone completely off, same result.

http://imgur.com/6375t5i [1]

Edit- One thing that was weird that also happened, was after I restored stock and then rebooted, I unplugged the charger and during the whole 'android is upgrading' thing where it shows the number of apps and such, the charger was unplugged and the phone stayed on for that entire duration. Then once it finished the upgrading thing, it immediately died. That is incredibly strange. Also someone mentioned maybe it's the charger plug in area not working properly, but that doesn't explain a battery going from ~70% to 0 instantly, and the phone not recognizing a charged battery and showing 0% even unplugged.

Also, in addition to everything above, even though I'm certain it's not a battery issue, I bought another official Samsung battery just because I really don't want an 800 dollar paper weight, and I know the battery was somewhat charged when I got it, and I put it in and have the exact same issue. I also just flashed stock firmware via Odin, same issue. I was able to do all of that with my USB plugged in -- but as soon as I unplugged it the phone turned off. This is so frustrating, I can't explain how much I would appreciate help, and maybe even send some money via Paypal for an answer to a fix.