1

I own a new MacBook Pro (bought three weeks ago).

Since I don't want to exhaust the 1000 expected full charge cycles this battery is rated at, I connect the MacBook with the power adapter when I'm working at home so I don't draw down the charge when AC power is available.

  • I connected my MacBook when it had almost 100 percent and since then it says that the power adapter is connected but the battery is not charging.
  • Now I have 80 percent left and the battery is still not charging.
  • I disconnected and connected the power, now it's charging.

I'm still worried if everything is okay. Are there are situations where the MacBook does not charge for good reasons or to explain why I didn't get the charge before 80% capacity?

2

Yes - the system management controller polls the battery infrequently, so when the first plug it in, sometimes the cable has some lint or just that the battery doesn't need charge. I wouldn't worry at all and I wouldn't keep the battery always full. In my experience, that causes them to fail far more often than ones that get exhausted due to 1000 cycles (or less) and then the battery being flagged as faulty.

Apple certainly doesn't initiate a charge when the battery is nearly full, so we would need to see the detailed power status to know if you're expected to charge.

Here's what that command shows when you have a fully charged MacBook and disconnect the power and reconnect the power - no charge happens, just a back on AC power message:

me@mac ~> pmset -g pslog
Logging IORegisterForSystemPower sleep/wake messages
pmset is in logging mode now. Hit ctrl-c to exit.
2019-01-26 11:03:35 -0600 IOPSNotificationCreateRunLoopSource
Now drawing from 'AC Power'
 -InternalBattery-0 (id=4194403)    100%; charged; 0:00 remaining present: true
2019-01-26 11:09:19 -0600 com.apple.system.powersources.timeremaining
2019-01-26 11:09:19 -0600 com.apple.system.powersources.percent
2019-01-26 11:09:19 -0600 IOPSNotificationCreateRunLoopSource
Now drawing from 'Battery Power'
 -InternalBattery-0 (id=4194403)    100%; discharging; (no estimate) present: true
2019-01-26 11:09:19 -0600 com.apple.system.powersources.source
2019-01-26 11:09:19 -0600 com.apple.system.powersources
2019-01-26 11:09:19 -0600 com.apple.system.powersources
2019-01-26 11:09:43 -0600 com.apple.system.powersources
2019-01-26 11:09:43 -0600 com.apple.system.powersources.timeremaining
2019-01-26 11:09:43 -0600 com.apple.system.powersources.percent
2019-01-26 11:09:43 -0600 IOPSNotificationCreateRunLoopSource
Now drawing from 'AC Power'
 -InternalBattery-0 (id=4194403)    100%; charged; 0:00 remaining present: true
2019-01-26 11:09:43 -0600 com.apple.system.powersources.source
2019-01-26 11:09:43 -0600 com.apple.system.powersources
2019-01-26 11:09:43 -0600 com.apple.system.powersources

Feel free to ask a follow on question if you want to post your power stats or have a question about system information and reporting battery health and full charge cycles. Just @ me in the comments with a link to the new question and I'll see it.

  • Thanks for your answer! I don't speak English that well so I have a question concerning your answer: Did I understand it right that the SMC is somehow looking at the battery condition when connecting the power adapter and thus then decide to load or not to load? So it decides at almost 100 percent that discharging is better than holding the high percentage? – Conny Jan 26 at 17:22
  • The SMC and firmware have the charge decisions - so they don't decide to charge and not charge based on things like 5 minute changes. They wait for several sample cycles. I believe your 80% charge wasn't correct, but that it was just a piece of lint. My expectation is charge starts when you reach 90% current capacity or even a little higher. Your English is very good. I bet way better than if I tried to write your preferred languages. – bmike Jan 26 at 17:23
  • What are "sample cycles"? I'll monitor the charging behaviour in the next days and maybe ask again if it still acts mysterious. Thanks for the compliment :) – Conny Jan 26 at 17:31

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