Is there a way to actively know that the battery draining from a plugged-in MacBook Pro is a result of the new Battery Health Management feature? I mean specific logs, or a hidden user interface element? Because I thought/think I have a faulty logic board and so many different Apple employees are treating it like a hardware issue when I'm realizing it might be the Battery Health Management feature. It's frustrating that the battery menu bar icon doesn't have a little mention of the feature being used to reassure the user that everything is intentional and operating as expected.
jent, yes, just toggle off the feature. You should not see that behavior persist. Please let us know.
After observing the BHM feature on my 99% plugged into AC 15" 2017 MBP for a month, this is what I can report:
Approximately every three days the built in charge controller stops energy going to the battery. The finder battery menu shows one thing down to about 95% charge, then another as is shown by my attached screenshots. It gets down to about 90% then starts charging right back to 100%. That's it.
Here it is at 95%:
At 94%:
At 90%:
And the Activity Monitor showing the BHM induced cycle:
As you can see, the Battery icon is showing fully charged and plugged in even when it is below 100% and even when it says "Battery is Not Charging".
Now whatever confidence you may have in Apple engineers to prolong the life of your battery, this behavior will not accomplish what the science shows. Here is an excerpt from just one knowledgeable source, Battery University (there are many others):
"A laptop battery could be prolonged by lowering the charge voltage when connected to the AC grid. To make this feature user-friendly, a device should feature a “Long Life” mode that keeps the battery at 4.05V/cell and offers a SoC of about 80 percent. One hour before traveling, the user requests the “Full Capacity” mode to bring the charge to 4.20V/cell."
Almost all batteries, including Lithium Ion and Polymer have a voltage associated with States of Charge (SoC). That is how the built in charge controllers know when to taper off the energy going to the battery and then provide just a small amount of energy (Watts) through amps (aka trickle charge) to keep it at 100% SoC. According to all the science I have seen, keeping these batteries at that 100% SoC all the time is not helping the longevity. But allowing the charge controller to keep the SoC at around 80% is good battery juju. And yes, you will only get 80% of your battery capacity, therefore toggle the feature off if needed to get back to fully charged.
I have spoke with three "Senior" Apple CS techs now and not one of them has a clue how the BHM feature was programmed. It's one thing to dumb down the features to a check box, but entirely different to provide no one with knowledge and have the white paper "About battery health management in Mac notebooks" no where near describe in detail the actual behavior, but does suggest that users like me should see it keeping a lower maximum charge. Doing that for less than one hour every three days is not going to accomplish the task.
The only people that may be confused by this are the people that actually have some technical knowledge and want to know if a new feature that is prolonging the inevitable cost of replacing a $200 glued in battery (that used to take less than one minute to replace) is actually working! With all the well documented glitches in the current macOS, it's quite prudent to allow people to be able to simply verify intended function.
If anyone else has anecdotes of their experience, please provide. I would like to know if there is hope for this feature, or should risk AlDente which does exactly what the science suggests should happen, even though having a third party write keys to the SMC firmware is something I definitely want to avoid. Maybe 10.15.6 which should drop in a few days will amend some glitches... ?
