MBA shuts down on battery and battery drain

Hello Guys,

I have a MBA 13” Early 2015. It seems that my battery is dying, but I am not sure what is the source of it. A month ago my sister and I compared our battery (she has the same MBA) and then Coconut Battery showed 98% battery life and about 200 cycles. But a few weeks ago I experienced it for the first time that my battery drains quickly, and when it shows about 30% Mac shuts down. After that when I plug in the charger and turn Mac on it shows zero percentage. Few days ago I checked it with Coconut, and it showed 82%. I made a clean MacOS install, did a SMC reset, but the problem is still here. Now Coconut shows 65.1% and it changes after every SMC reset. (for example before I made the reset today I had 64.1%…)

What a !&&* is going on? This computer is about 2 years old, and in a very good condition. I care about and never did any radical thing with it.

Here is some new experiences: I usually plug in my iPhone 6s while working on battery. (my phone is a hotspot via USB) If it is not plugged in, the only problem is the draining, but Mac does not goes to sleep earlier then 0-1%. BUT: while iPhone is plugged in it goes to sleep randomly with a low battery percantage. (about 20-30 - never goes down to 0-1%). If I try to turn Mac on, it is unable. After few minutes I can turn it on, and shows almost the same % what I realized before it went to sleep. But: if I plug in the charger immediatelly after the shut down, Mac shows 0%. So this is why I am not sure what is this big mess around my Mac… Please help me!