Why does my MacBook M3 Max with 96W power supply run out of power on MagSafe but not 60W USB-C?

harlekkin wrote:

GPT is trying to tell me that my Mac is throttling on USB-C 60W and not so on 96W Magsafe, but then why the **** would Apple build their system to allow this? If the 96W charge isn't powerful enough for a M3 Max, why supply one? What am I missing here?

As much as it pains me, I think ChatGPT might have this one.

What I think you're missing are other devices. What you are describing sounds like a classic CPU throttle. This is often caused by a faulty video dongle. Perhaps when you are swapping around power sources and USB plugs, you are changing the configuration to the point where the throttle isn't happening for whatever reason.

In the past, this was easy to observe because the old Intel Macs would slow down to glacial speeds and the fans would ramp up to jet engines. But with the new Apple Silicon devices, their glacial speeds are probably still faster than Intel speeds. They don't need those massive fans so you don't hear that either. All you notice is the battery draining while plugged in.

So an easy test is to disable all 3rd party hardware connections of any kind. Leave only MacSafe connected. If you can reproduce the problem, then that's a hardware fault for Apple to fix. If the problem goes away, then it was caused by one of your external devices - most likely a video dongle. You'll have to do trial-and-error to find out which one.

FYI, I have seen several M-series Macs have Logic Board failures due to not being able to charge the battery when using Magsafe, but was fine charging with USB-C charging cable. I have also seen a few other posts on this forum where people reported Magsafe charging failures and they were resolved after Apple replaced their Logic Boards.

I'm starting to think there is a hardware problem here.

harlekkin wrote:

I've had this problem straight out of the box. Got my new 96GB RAM 4TB 14" MacBook Pro M3 Max, and while I was doing some Lightroom and Premiere, I noticed that whilst plugged into Magsafe, the power would drain rapidly. Eventually, I had to set it to "Low Power" to continue working or risking the battery going flat. Whilst plugged in to 96W of power.

Decided to try USB-C running at 60W with the same 96W power adapter. Runs like a charm. Even when on "High Power" my Macbook has never ran out of battery even when processing heavy video and drain is very slow.

Swapped back to my Magsafe just to try again, and whilst my Mac was fully charged and doing nothing of significance - I left it plugged in to Magsafe - 30 minutes later I returned to find it had drained to 80% battery whilst, apparently, still charging.

GPT is trying to tell me that my Mac is throttling on USB-C 60W and not so on 96W Magsafe, but then why the **** would Apple build their system to allow this? If the 96W charge isn't powerful enough for a M3 Max, why supply one? What am I missing here?

I would prefer Magsafe of course since it's purpose is to not use up my USB-C, but what's the point when I can't allow my Macbook to do anything whilst plugged into it. Complete and utter BS. Has anyone else bumped into this?

[Edited by Moderator]

I didn't track the totality of your issue ... however

Are you new to Mac or Mac laptops...and Battery Health Management; the 80% caught my eye.

80% is the happy place to hold the battery for the long game. Try Control click the icon and see if you have the option there...

The rule of thumb—if you are near the mains leave it plugged in, if you need the portability then run on the battery only—this is how you help optimize your battery charging and extend the working life of your battery by reducing the cycle count.

You can read up to help assess the situation

About BHM battery health management:

M1/M2/M3/M4 SoC

About battery health management in Mac notebooks - Apple Support

If your MagSafe cable or power adapter isn't working

Unplug the power adaptor from the wall, wait 60 seconds and then plug the adaptor back in.

If your MagSafe cable or power adapter isn't working - Apple Support

If your Mac battery status is “Not Charging” - Apple Support

If your Mac battery status is “Not Charging” - Apple Support

A SafeBoot Start up your Mac in safe mode - Apple Support will sort many anomalies

then Reboot as normal and test.

Keep in mind your 90 days of complimentary telephone support begins on the date of purchase, if you need to sort it further

Call Customer Support (800) MY–APPLE (800–692–7753)

Sorry, but no one will be able to diagnose a hardware issue over a post. It will require diagnostics and would suggest taking it to the Apple Store by scheduling an appointment. At the very least contact Apple directly using the link here:

Contact Apple Support - Apple Support

To be honest, I have not seen any other reports here, but there is obviously a problem that needs addressed.

Yea, the cable and cleaning the MagSafe port would be a recommendation, but that still would not explain a 80% drop in 30 minutes, even it it wasn't charging. Everything would point to a bad battery, but that is just not likely with it being only a year old, reporting a Battery Health of 91%, and that fact you had this problem from the start. It is possible, just not likely and something that would likely require diagnostics by Apple. Please update if you do find anything else out.

Another common troubleshooting test is to Factory reset and test before restoring from a backup, but I even hesitate in making such a recommendation, since I honestly don't believe this is related to a software problem where that would do any good.

It does make it very difficult that you are in a location without an Apple Store. I try to refrain from giving users a list of things to try unless I am comfortable that something I have to offer is actually going to help. I do think it is going to take some kind of intervention by Apple for a diagnosis, but please update if you do find anything else out.

To be clear the 94W you see in System Diagnostics does not mean that the battery is charging at 94W. If this is what you are looking at, it has just identified the charger and using the correct charging port capable of 94W. You can see in this screenshot that the battery is not even charging.

Great job on your graphics and very informative. I believe you are on the right track with cable, port, or internal component. Let's hope a cable swap will solve the problem.