16" MBP Charging with 96W power brick

fehhkk

macrumors 6502a
Original poster
Jun 11, 2009
665
118
Chicago, IL
Screen Shot 2020-02-24 at 3.54.01 PM.png


I've noticed that the stock 96W power block for the 16" MBP isn't able to sustain 96W charge rates, is it only me? When I'm connected to a 60W or 85W charger, I don't see power delivered this way.
 

fehhkk

macrumors 6502a
Original poster
Jun 11, 2009
665
118
Chicago, IL
I can't recall exactly, but I had 1h 15m left more or less, I guess around 20% or so, and was using the Radeon 5500M graphics card.
 

satinsilverem2

macrumors 6502a
Nov 12, 2013
748
228
Richmond, VA
my 13" MBP almost never maintains its 60 watt peak consumption. Even when the battery is around 10-20 percent its only around 45-50 watts unless im charging and hitting the CPU and GPU at the same time.
 

bearda

macrumors 6502
Dec 2, 2005
459
75
Roanoke, VA
It's possible it can't throw that much into the battery, and the extra overhead is for power consumption for the system while it's charging.
 

jerryk

macrumors 603
Nov 3, 2011
5,802
2,910
SF Bay Area
Looking at this again. I wonder if it needs to maintain peek charge rates. After all once the battery is full, it is full. Until something drains it down there is no need to charge. So to me it seems like the charger outputs full rate until the battery is full, and then steps down to a lower rate. They when the battery charge drops enough the charger steps up to the higher rate. Repeated over and over.

The reason the lower output chargers continuously output at max rate is because your load is high enough to prevent the battery from getting full.

My EVs do the same thing with regen braking. If there is not uncharged space in the battery (i.e. State of charge is high), no regen braking since there is no place for the charge to go.

Try this. Run what every load you are running. Unplug the charger. Let it run the battery down for a bit. Then plug in the charger. If it shoots back up to high charge rate good. And if it starts doing this cycling after the battery is full the mystery is solved.
 

Camarillo Brillo

macrumors 6502
Dec 6, 2019
278
230
What you’re seeing is how much power the computer is asking from the power supply. It varies based on all sorts of things, mainly cpu and gpu load and battery level, it doesn’t always need 96 watts.

In fact under a high load these computers will actually take more than 96 watts and then they’ll start draining battery power while plugged in.
 

thatvirtualboy

macrumors newbie
Aug 25, 2015
5
3
Not to hijack the thread.. but is it safe to use the 87W Power Adapter from an older MBP on the new 16" MBP?
 

jerryk

macrumors 603
Nov 3, 2011
5,802
2,910
SF Bay Area
Yeah I figured the machine doesn't really need sustained 96W.

Looking at Apple's USB-C charge cables, the one that ships with the 87W and the 96W power adapter seems to be the same.

USB-C cables are 100 or 60W. If the cable is not 100W certified and chiped you cannot push more than 60 W (20V @ 3 A) max. With appropriate chipping and certification you can push 100 W (20A @ 5V) max. And within these limits the Power Supply and Device decide what is the best Amps and voltage. So USB-C Power Deliver is not some sort of dumb pair of wires and dumb power supplies. This negotiation goes on to determine the max amount of power than can be safely delivered.
 

Hexley

macrumors 65816
Jun 10, 2009
1,006
99
It wouldnt make sense to accept the whole 96W when the battery is already 100W.

I use my 5W iPhone charger with my 16" when it's 100% It can sustain it's 100% even then.

But then again I was only using a dozen tabs of Firefox.
 
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