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User profile for user: hervebcn
hervebcn Author
User level: Level 1
8 points

Macbook pro 16" power spikes when turning on

Hi guys,

I have a 2019 Macbook pro 16" since march 2020, so 10 months old. The other day I realised it was not charging at all, investigating I saw that the system was detecting a 96W power supply but only charging at 60W. After trying unplugging and plugging back the UBS-C cable, realised that could have been the origin of the issue. (for a day it stopped charging at all, and all the USB-C ports stopped working for a little bit, eventually now its working fine again)


Now the system detects the power supply as


I recently noticed my battery health is already 82% and the machine is only 10 months old.


I started monitoring power usage and realised that every time you turn on the machine, the system power usage spikes at more than 98 W (I even saw spikes of 110 W) wen the power supply can only feed up to 94W, but on these spikes the DC was only feeding around 70 or 80 W, which leave the rest to be provided by the battery. (I used istat menus to check the power issues)


I don't know if this behaviour is normal... but I strongly believe that those spikes in energy consumption will make the battery to die earlier than expected... mine is already at 82% health only in 10 months. If that is the case, I just spent 3.6k on a machine that needs a battery service that costs 200 every year or so?

Does anyone know if this behaviour is expected?

MacBook Pro 16″, macOS 10.15

Posted on Feb 8, 2021 3:50 PM

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User profile for user: Branta_uk
Branta_uk
User level: Level 7
32,666 points

Posted on Feb 8, 2021 5:03 PM

Your MacBook is 10 months old, so you have roughly another 2 months of warranty to make your decisions.


From the details you posted I am not convinced you have a real problem. There are several factors which need a more detailed check before you are sure.


Start by checking your charging cable, because there are several different grades. See details the section about half way down the page in Find the right power adapter and cable for your Mac notebook - Apple Support for how to find and decode the cable's serial number.


A reset for the SMC might be a good start in troubleshooting and won't do any harm. How to reset the SMC of your Mac - Apple Support. Also see the notes in Determine battery cycle count for Mac notebooks - Apple Support


Seeing a lower than maximum rated power delivery is not necessarily a problem, because the rating on the power adapter is simply the design maximum. Your MacBook Pro has intelligent charging circuits which will regulate the power actually delivered, and it may be that the battery was approaching maximum and the charge rate had been reduced. This is perfectly normal, charge at max rate to about 50-60% then top off at reducing rates to avoid excessive heat generation.


There is a Smart Charge function in recent builds of MacOS, which learns your typical usage and will delay completing the charge until you are expected to need the battery. The purpose of this is to avoid holding the battery at 100% charge for prolonged periods, which can have an adverse impact on battery life. Also have a look at the notes in Get help with your Mac notebook battery - Apple Support


Seeing a power delivery more than the expected rating of the power adapter might not be a major concern for several reasons.

(a) You are seeing short duration power spikes, and the mean power draw appears to be comfortably within the rating of the adapter. If there is a problem it is likely the adapter will become significantly hot to touch. If it isn't getting hot it is unlikely to be overloaded.

(b) The power adapter will protect itself if it is overloaded.

(c) Your monitoring software looks like it might be a third party product which is likely to be uncalibrated. You are seeing instantaneous power loads which are within about 10% of expected maximum continuous rating so there is probably nothing to worry about there.

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User profile for user: Branta_uk
Branta_uk
User level: Level 7
32,666 points

Feb 8, 2021 5:03 PM in response to hervebcn

Your MacBook is 10 months old, so you have roughly another 2 months of warranty to make your decisions.


From the details you posted I am not convinced you have a real problem. There are several factors which need a more detailed check before you are sure.


Start by checking your charging cable, because there are several different grades. See details the section about half way down the page in Find the right power adapter and cable for your Mac notebook - Apple Support for how to find and decode the cable's serial number.


A reset for the SMC might be a good start in troubleshooting and won't do any harm. How to reset the SMC of your Mac - Apple Support. Also see the notes in Determine battery cycle count for Mac notebooks - Apple Support


Seeing a lower than maximum rated power delivery is not necessarily a problem, because the rating on the power adapter is simply the design maximum. Your MacBook Pro has intelligent charging circuits which will regulate the power actually delivered, and it may be that the battery was approaching maximum and the charge rate had been reduced. This is perfectly normal, charge at max rate to about 50-60% then top off at reducing rates to avoid excessive heat generation.


There is a Smart Charge function in recent builds of MacOS, which learns your typical usage and will delay completing the charge until you are expected to need the battery. The purpose of this is to avoid holding the battery at 100% charge for prolonged periods, which can have an adverse impact on battery life. Also have a look at the notes in Get help with your Mac notebook battery - Apple Support


Seeing a power delivery more than the expected rating of the power adapter might not be a major concern for several reasons.

(a) You are seeing short duration power spikes, and the mean power draw appears to be comfortably within the rating of the adapter. If there is a problem it is likely the adapter will become significantly hot to touch. If it isn't getting hot it is unlikely to be overloaded.

(b) The power adapter will protect itself if it is overloaded.

(c) Your monitoring software looks like it might be a third party product which is likely to be uncalibrated. You are seeing instantaneous power loads which are within about 10% of expected maximum continuous rating so there is probably nothing to worry about there.

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User profile for user: hervebcn
hervebcn Author
User level: Level 1
8 points

Feb 8, 2021 5:13 PM in response to Branta_uk

Hey Branta,


Thanks for the quick reply, everything started when the laptop was not charging at all and the ports were not responding. you could plug it and not response from it, or it would chime for a second and stop almost instantly. Then the battery health started dropping, earlier on this week it was at 86%


The cable and everything are the ones supplied by apple that came in the box so yup, used the official 100W cable and 96W power supply.


The battery keeps dropping battery health with just 46 cicles and 10 months. I guess I will have to request support form apple since something went wrong with it.


They always ben super helpful to be honest, Ill give it a go, I am just worried about the battery lifespan of the battery long term.


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Macbook pro 16" power spikes when turning on

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