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User profile for user: HH-0
HH-0 Author
User level: Level 1
8 points

Battery starts to drain while plugged in

I just bought my MacBook Pro 2020 13'' recently. I have an external monitor, Bluetooth mouse and keyboard.


I use my MacBook plugged in most of the time. However, sometimes I notice the battery % starts dropping while plugged in when I work on Xcode. From 100%- 96%, the status says "Battery Charged, Power Source: Power Adapter". When it reaches 95%, the status switches to "Battery Not Charging, Power Source: Power Adapter".


Normal restart or re-plugging the adapter did not help. An interesting issue I noticed was when I did a restart, the battery % at the login screen showed a lower value (89% or something) compared to the battery % when I was logged in (94% or something). I tried to restart when it said 94%.


A complete shutdown and power back on or SMC reset seems to fix the issue. However, this issue happens again in 2 or 3 days and I would have to do a complete power off and power on again. It's been like this for over a week now.


I greatly appreciate if anyone could help or provide any suggestions.


Thank you

MacBook Pro 13″, macOS 10.15

Posted on Jul 13, 2020 5:50 PM

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
128,905 points

Posted on Jul 13, 2020 6:06 PM

Your computer performs best when connected to AC power. It can use the full output of the Power Adapter AND when doing especially challenging work will also freely "borrow" power from the battery. In some cases, the charged state may even decline during stressful work.


When used only on battery, your computer has no extra cushion of power, and will perform more slowly. However, for ordinary non-stressful tasks this may not be objectionable (possibly not even noticeable.)


In general, you should ALWAYS connect AC power when it is possible to do so, and only run on batteries (which will be somewhat slower) when no AC sources are at hand. There are three micro-controllers cooperating on battery and charging issues, and your Mac will NEVER over-charge.


A charge cycle is ever-so-slightly destructive to batter longevity. When operating as designed (and not using Battery Health Management) battery charge level is allowed to decline to about 92 percent level before initiating a recharge cycle to top up to about 99 percent.


The latest Catalina software update for MacBook Pro with T2 chip (2016 models and later) includes a new feature called Battery Health Management. Based on you usage patterns, this widens the hysteresis to initiate a charge cycle at a lower level, and stop before 99 percent.


About battery health management in Mac notebooks - Apple Support

https://support.apple.com/en-us/HT211094


This relaxes the set points around re-charging (based on your usage patterns) and can improve long term battery lifetimes. When active, recharging may stop short of 100 percent charged.


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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
128,905 points

Jul 13, 2020 6:06 PM in response to HH-0

Your computer performs best when connected to AC power. It can use the full output of the Power Adapter AND when doing especially challenging work will also freely "borrow" power from the battery. In some cases, the charged state may even decline during stressful work.


When used only on battery, your computer has no extra cushion of power, and will perform more slowly. However, for ordinary non-stressful tasks this may not be objectionable (possibly not even noticeable.)


In general, you should ALWAYS connect AC power when it is possible to do so, and only run on batteries (which will be somewhat slower) when no AC sources are at hand. There are three micro-controllers cooperating on battery and charging issues, and your Mac will NEVER over-charge.


A charge cycle is ever-so-slightly destructive to batter longevity. When operating as designed (and not using Battery Health Management) battery charge level is allowed to decline to about 92 percent level before initiating a recharge cycle to top up to about 99 percent.


The latest Catalina software update for MacBook Pro with T2 chip (2016 models and later) includes a new feature called Battery Health Management. Based on you usage patterns, this widens the hysteresis to initiate a charge cycle at a lower level, and stop before 99 percent.


About battery health management in Mac notebooks - Apple Support

https://support.apple.com/en-us/HT211094


This relaxes the set points around re-charging (based on your usage patterns) and can improve long term battery lifetimes. When active, recharging may stop short of 100 percent charged.


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Battery starts to drain while plugged in

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