Is it a battery problem or SMC problem?

Question

I have a mid-2015 MacBook Pro running High Sierra. Except when I'm traveling, I always use it in clamshell mode and connected to power. I rarely put it to sleep (I have Energy Saver set to just put the display to sleep).

On July 21 I noticed that the light on the power connector had gone to amber, but Energy Saver said that the battery was fully charged. However, coconutBattery said the battery was at 95%.

Today I noticed that the lightning bolt was no longer showing on the battery status in the menu bar, and when I click on it it says "Battery is not charging". Energy Saver says that the battery is at 97%, but coconutBattery says 81%. Here's its full report:

Current Charge	6347 mAh
Full Charge Capacity	7092 mAh
89.5%
Design Capacity	8755 mAh
81%
Manufacture date	2018-03-07
Cycle Count	31
MacOS battery status	Good
Battery temperature	37.0°C
Charging with	0 Watts
Power adapter	Connected

Does this look like a problem with the battery, power adapter, or SMC?

UPDATE:

I reset the SMC, and at first it seemed like the problem was solved. The battery item in the menu bar said it was charging, and eventually said it was fully charged, and the power adapter changed to green. At that time coconutBattery said:

Current Charge	7030 mAh
Full Charge Capacity	7030 mAh
100%
Design Capacity	8755 mAh
80.3%

But while I was posting an answer to the question, it changed to:

Current Charge	6766 mAh
Full Charge Capacity	7029 mAh
96.3%
Design Capacity	8755 mAh
80.3%

The adapter light is still green.

UPDATE 2

The adapter light changed to amber a couple of days after the above update, and the menu says "Battery is not charging". Energy Saver says that the battery is at 98%, but coconutBattery says 76%. Its history viewer shows:

Date                Health%     Charge Capacity Cycles
2021-08-01 17:21:28 80.29697    7030    8755    31
2021-08-02 09:10:45 80.28555    7029    8755    31  
2021-08-03 10:01:09 80.01142    7005    8755    31
2021-08-06 00:53:35 77.72701    6805    8755    31
2021-08-09 13:33:42 76.02513    6656    8755    31

And System Information says this in the Power tab:

Battery Information:
Model Information:
      Serial Number:    C018104BAG5FWLMF1
      Manufacturer: DP
      Device Name:  bq20z451
      Pack Lot Code:    0
      PCB Lot Code: 0
      Firmware Version: 702
      Hardware Revision:    1
      Cell Revision:    3241
Charge Information:
      Charge Remaining (mAh):   5959
      Fully Charged:    No
      Charging: No
      Full Charge Capacity (mAh):   6623
      Health Information:
      Cycle Count:  31
      Condition:    Normal
      Battery Installed:    Yes
      Amperage (mA):    0
      Voltage (mV): 12252
AC Charger Information:
Connected:    Yes
  ID:   0x0100
  Wattage (W):  85
  Revision: 0x0000
  Family:   0x00ba
  Serial Number:    0x00f277bf
  Charging: No

So what should I look for to understand why the battery is draining instead of charging?

I tried putting the computer to sleep for a few hours yesterday, it didn't help.

Answer 1

You need to get the battery replaced. Even if it isn't flagging the 'Needs Servicing' flag, it's six years old, draining rapidly, with a diminished capacity.

80% of original capacity is Apple's threshold to replace the battery. If it's under warranty, they'll do it for free. If not (and yours isn't), you'll have to pay.

If the capacity is much higher, they'll tell you it's fine and to come back when it's lost a bit more!

It's around $200, but the good news is that because of the design, they actually replace the entire 'top half' - the keyboard, trackpad and upper case. So it's a pretty good investment to prolong the life of your Mac.

Answer 2

Your battery is rather old ( ~ 3.5 years ) and had a rather very small cycle count ( ~ 30 ). Then its high level of charge slowly decreased.

I suggest you to fully discharge your battery in one pass. Unplug your Mac, and let it go to the point where it will make a forced shutdown or switch on hybernate mode. See pmset -g | grep hibernate. When you reach the 5 % level, take care to save any open file, and even better, close any open application.

Next fully charge it in one pass and to its max charge reachable. Check again the output of coconutBattery. If its current charge is pretty near 80% again, then you should planify your battery replacement.

You don't have to tinker with the SMC ( this is rather a religious trick from bad guys working in support and who respect procedures rather than analyzing problems ). Many users who apply this reset of the SMC conclude it fixed their problem when in fact in the cases I throughly checked it is just the reboot of MacOS which fixed it.