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My 15 inch 2018 Mac Book Pro with Mojave 10.14 randomly starts draining battery when plugged in. When I try to move the cable, change the power cable to a different USB slot nothing helps. The battery indicator is in charging state, but when pressed, it says "Not charging". After some time, when it gets to 88-92% it suddenly starts charging again. I noticed that this happens independently of loads. Once or twice a day. This can happen when 2 IDE, browsers windows, media player are running simultaneously, and when it is in idle state showing only desktop. I'm using native 85Watt charging block and cable.

Additional info: In System Report -> Power, the Condition is displayed as Normal. With cycles count equal to 52. This used to happen even when the condition used to be better, with fewer cycles count. But less frequently.

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  • Click on the battery icon in the menu bar, does it say service battery ? – anki Jul 3 '20 at 10:47
  • @ankii Nope. And in System Report -> Power, the Condition is displayed as Normal. With cycles count equal to 52. This used to happen even when the condition used to be better, with fewer cycles count. But less frequently. – OlehZiniak Jul 3 '20 at 11:07
  • This has some great information. Would you consider an edit to ask a question so we know what practical problem you face? I don’t see a clear question that could be answered from the text of the first version of this question. – bmike♦ Jul 3 '20 at 11:23
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Update 2020-08-05: It's a new feature by Apply and intended behavior

see HT211246

If you see 'Not Charging' when your Mac notebook is connected to power Depending on its settings, your Mac might temporarily pause charging to help calibrate battery health management, a feature designed to improve the lifespan of your battery.

If your Mac notebook has Thunderbolt 3 ports and uses macOS Catalina 10.15.5 or later, you can use battery health management to help extend the life of your battery. Battery health management is designed to improve your battery's lifespan by reducing the rate at which it chemically ages. The feature does this by monitoring your battery's temperature history and charging patterns.

When battery health management is turned on, you might occasionally see ”Not Charging” in the battery status menu of your Mac, and your battery's maximum charge level might be lowered temporarily. This is normal, and it's how battery health management optimizes charging. Your Mac resumes charging to 100 percent depending on your usage.

This is a new behavior, in my opinion – and might be a bug (see update)

I have not noticed this behavior till recently (see below). I cannot remember observing a noticeable/quick discharge while connected to the power supply, and when this started to happen I thought the laptop is broken or the SMC/nvram corrupt…

What is happening now is that the Laptop (in my case also a MacBookPro 15" 2018) stops charging for a period of time (around 1 h). Maybe till it reaches ~93% remaining charge and then starts charging again.

I have noticed this since installing the 002 or 003 security update on High-Sierra, I have then tried a lot to troubleshoot this new behavior, updated to Mojave (with all updates), reset the nvram and power management but the issue persists.

The screen-shots below, from the iStat menu sensor data recording, show how the battery is draining (while still connected to the power supply). The DC input from the power supply is reduced to 2 W (20 V at 0.1 A) and power is (mainly) drawn from the battery.

Battery charge drops to ~93% while connected to power supply
above: Battery charge drops to ~93% while connected to power supply

Battery powers system, while connected to power supply
above: The battery powers the system, although it's connected to power supply

Power input from the connected power supply
above: Power input from the connected power supply

This only happens when the laptop is awake and always at the same time of day. When it is not awake at that time it will start draining the battery the moment it is awake.

This continues to happen with different chargers and when booting to recovery mode, and - I think - when booting an older system from external drive.
I suppose that maybe something in the SMC code was changed, which triggers this behavior independent from the OS.

All in all this new behavior has perplexed me quite a bit.

I do not see how a daily forced discharge to 93% can prolong the overall life of the battery!

Right now Apple is forcibly adding one full discharge/charge cycle about every two weeks, or ~25 full cycles per year. Maybe (and I hope so) they have done some research and determined that this behavior actually prolongs the battery-lifetime – on the other hand this might just be a bug…

Update 2020-08-05: It's not a bug but "a feature designed to improve the lifespan of your battery", according to Apple

The way Apple back-ported this behavior to High-Sierra and Mojave, where there is no "Battery health management" in System Preferences/Energy Saver still makes me wonder if this is working entirely as intended.

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  • I find this answer very helpful, and I share your skepticism. apple.stackexchange.com/q/400462/143729 – uhoh Sep 2 '20 at 3:20
  • Keeping your battery at 100% is bad for it, so it may well be worth it to add cycles if it means the average storage capacity is closer to 90% – BallpointBen Oct 12 '20 at 16:30
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This is normal behavior.

The key to your question is your estimation:

After some time, when it gets to 88-92%

That is right at the line (93%) where Apple estimates that charging will appear to stop. A couple of percentage points is well within the margin of error and it's safe to say it wasn't a scientific observation you were making.

From Apple Support: About Mac notebook batteries

My battery won't charge to 100%

Occasionally, the battery might not show a full charge (100%) in macOS, even after the power adapter has been connected for an extended period of time. The battery might appear to stop charging between 93 percent and 99 percent. This behavior is normal and will help to prolong the overall life of the battery.

The thing is, depending on use, it may go a little lower than 93%. Most things done with battery is done based on calculation of what's measured so 93% is a calculation. The point is, a hard 93% would not be that the demarcation of when to start charging. Like everything else, it is based on the measurement; and in this case, most likely the measurement of the remaining charge and max charge values read directly from the battery itself and not a calculation displayed by the OS.

Regarding Catalina

Catalina introduced a Battery Health Management feature and released it to the public June 1st 2020 in the 10.15.5 Update. The Support article I sourced the info from above is from May 26th, 2020 (Pre-Catalina, see image below).

enter image description here

Apple has a habit of not dating things or just showing you when things were updated so, took a screen grab for posterity

It's also been in the public beta for some time judging by the ample blogs/articles written about it. Now, it wouldn't be uncommon for Apple to implement a portion of the the feature (like changing the max charging limit) into earlier versions of macOS. The full "Battery Management" feature allows you the ability to control it.

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  • So looks like your old answer suggesting that it doesn't really matter wasn't entirely accurate after all – Skeleton Bow Jul 11 '20 at 22:31
  • I'm a pragmatist @SkeletonBow - many folks focus on the minutiae of things like micro-managing the charging process. In the end, did they really save anything? If this stuff gave you years more - I'd be all for it. But Apple still only warranties the batteries for up to 3 years (with AppleCare; 1 year without). If this BHM feature was so great why not bump it to 18 months default and 4 years with AC? Because they know how trivial it all is. – Allan Jul 11 '20 at 22:38
  • Sure, I get that, but if it's so trivial, why would Apple spend the time and resources including this as a feature in the first place? – Skeleton Bow Jul 11 '20 at 22:40
  • Noise. Or to use the old adage "squeaky wheel gets the grease." Apple made the idiotic move of slowing performance when the battery got low without telling people so that was another huge helping of crap piled onto the plate of misunderstanding of how battery charging works - too many myths out there. It's kinda like how resetting the NVRAM/SMC is the solution to everything. When I worked in Tech Support (very, very early in my career), we were taught to gently BS the customer to the actual answer. Same thing happening here. – Allan Jul 11 '20 at 22:46
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    There are things Apple does that make you wonder if they ever learn from their past mistakes. – Allan Jul 11 '20 at 22:56
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This feature was introduced in macOS Catalina, on by default. Are you sure you're actually on Mojave?

It's supposed to prolong your battery life, you can disable it in Energy Saver -> Battery Health.

More info here

PS: would comment, but don't have reputation

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  • Nope, I'm pretty sure that I see macOS Mojave Version 10.14.6 in "About this Mac". In Energy Saver, I don't see "Battery Health" anywhere. Not sure if this is has something to do with a fact that my machine is managed by company Administrator. – OlehZiniak Jul 3 '20 at 12:15
  • well you can upgrade to Catalina and tren try disabling it :) – Dude Jul 3 '20 at 12:28
  • unfortunately, this is not the case, because I don't manage updates on this particular machine. – OlehZiniak Jul 4 '20 at 12:38
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I have a similar issue while using a MacBook Pro (15-inch, 2018) running Catalina (10.15.x). What I've discovered is that my USB dock is the problem. I am using a Sicotool dock which has several USB ports, a USB-C port, ethernet and some display ports. I have everything connected to this dock (monitor, two USB drives, ethernet, power) so I have an easier time plugging in just one cable. What I believe is happening, the dock overheats. When I notice that my laptop is no longer charging while plugged in, an unscientific test of the temperature (by touch) indicates to me that the dock has grown too hot and some how shuts off the flow of power (or maybe it's the laptop itself). What I do is unplug my USC-C power from the dock, plug it in directly to the laptop for a while and then after the dock cools down, I can return the power cable to dock. This happens about once a month for me on average.

I have also had some success with just unplugging everything from the dock, unplugging the dock from the laptop and then reconnecting everything to enable the power to flow again. Not sure if that resets any hardware/software running in the dock.

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    For me, this even happens when the charging cord is directly plugged into the laptop, and no additional hardware is plugged. – OlehZiniak Jul 13 '20 at 12:32

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