MacBook Pro (16-inch, 2019) Battery Drain While Charging

MacBook Pro 2019

I have also noticed the battery discharging when teaching a 1-2 hour class using Zoom with three external monitors connected to my MBP (clamshell mode). My setup includes the 96-watt power supply connected through an Apple USB-C to Digital AV Adapter. Based on what was posted in these threads, I discovered that the Apple USB-C to Digital AV adapter, which I use to connect one of the monitors and the original 96-watt power supply (previously mentioned), only passes 60 watts of power! Once I connected the power cord to the MBP directly, it increased to 94 watts (although my MBP identified it as a 96 watt PS). Time for a longer HDMI cord so I can have the power supply connected directly to the MBP and the Apple USB-C Digital to AV Adapter on a different USB-C port. Thanks to all for helping solve this issue.

Take away: The Apple USB-C to Digital AV adapter will only pass 60 watts of power.

NB001 wrote:

To Steve626,

Thank you for your detailed explanation. I've had the same issue for weeks now, and even apple care didn't know how to address it. I googled Battery Health Management and read the documentation provided by apple. As you mentioned, it modifies charging patterns to improve battery aging. But I didn't see any mention in the article about draining the battery to about about 90%-92% before charging. Actually, mine started doing that after the latest update. Drains to 92%-93% and starts charging.

Could you please post where you found that information? Just for future reference.

Thanks again.

I observed it on two new 2019 MacBook Pro 16" computers. Others posted in these Apple Discussions about this and indicated as such. I don't have the exact reference but you can find mention of it in the Apple Discussions and elsewhere on the internet in various Mac forums. The behavior is extremely repeatable. Of course it only works properly if you are using a proper 96-watt charger to get the full power.

If this is correct, someone should tell the Apple employees. I'm now on my second MacBook Air *this month.* The first one had the power drain, exactly as described. It would drop to the low 90s, then climb back up. Spoke to an Apple support person on the phone and she walked me through the system management reset. Didn't help. Took it to the Genius Bar and the guy told me that they would need to swap out a logic board or give me a new computer.

Step 2: I *bought* a second MBA, migrated everything from the first to the second, wiped the first, and returned it. New power adapter, new cable, new computer. Same issue. Finally in frustration, I bought an external SSD, backed up all my data, wiped the new MBA, started fresh and installed almost no software on it beyond a couple of key apps. And I watched it for several days. I never caught it going through the power cycle until tonight, 10 minutes after I installed Zoom. I deleted Zoom (just in case) and started searching the internet for info. Stumbled across this thread.

I've now turned battery management off. We'll see if that helps. I guess I don't much care if the battery cycles, but my question is if I get on a plane and I *start* down 90%, seems like that could be a problem. If I travel, I want full charge when I walk out the door. (Obviously not traveling right now, but I will in the future.)

So Apple...if you're reading this...TELL YOUR EMPLOYEES AND CUSTOMERS WHAT'S GOING ON. Or else expect a lot of returned computers with nothing wrong with them. Education is a good thing. Saves money in the long run, and maybe I wouldn't have wasted 20 hours of my time trying to "fix" an issue that isn't an issue. The "genius" thought it was a logic board. I still have an open ticket after my second call to support. Ridiculous.

</rant>

There are variety of cables available. Using the wrong one can cause problems.

Apple sells a Thunderbolt 3 cable rated to 100 watts. This can be used to maximally charge the 16" new Macbook Pro (the Mac laptop that presently requires the most watts) and it can also transfer data at up to 40 Gbps (10 Gbps when used in a USB 3.1 Gen 2 interface).

Apple currently sells a USB-C charge cable that will work with the 96-watt power supply on a 16" Macbook Pro. However, older USB-C cables may be rated to a lower wattage, and hence would not properly charge a 16" Macbook Pro 2019.

Third party cables should be scrutinized before purchase to ensure that they are rated to the right wattage and/or data transfer that you expect or need.

Not always Steve.

When playing a game, the 16" macbook pro might use more power then the charger can provide, resulting in battery drain while powered.

As far as I know the Battery Health Management option has not effect on this specific behaviour

Oh!! So the cable is 3rd party. I got duped, from the seller. Ok, so I will go and buy an original usbc cable and use the same adapter. That should give me the 87w. I think I understand.

many thanks!!!!

I have this problem with a brand new 2019 MacBook Pro 16". I bought the computer direct from Apple. I am using only the Apple-branded charger and cable that came with the computer.

The laptop is always plugged in. During the night, the computer runs a backup that takes several hours. Although the laptop is plugged in to the charger, the battery drains down to 20% or so. In the morning, the menu bar will indicate that the battery is not charging at all.

The SMC has been reset several times. I have reinstalled the OS several times, using both Recovery and Internet Recovery.

Apple support told me that the only remaining step is to send the computer in to have the motherboard replaced. The customer service rep advised against doing that, saying that I should return the computer for complete replacement instead.

I now have a new 2019 MacBook Pro 16" which just arrived from Apple's factory in China. It has exactly the same defect. I have reset the T2 chip several times and reinstalled the OS several times, but the problem persists.

It's quite clear that the problem is not due to off-brand chargers or cables. It seems likely that there's a firmware bug here.

Apple will probably realize this and fix it in the future. Note that large corporations are very resistant to learning about problems with their products, so it will likely take many months and quite a few complaints before this comes to the attention of anybody at Apple with any decision-making authority.

sophieogle wrote:

I have this problem with a brand new 2019 MacBook Pro 16". I bought the computer direct from Apple. I am using only the Apple-branded charger and cable that came with the computer.

The laptop is always plugged in. During the night, the computer runs a backup that takes several hours. Although the laptop is plugged in to the charger, the battery drains down to 20% or so. In the morning, the menu bar will indicate that the battery is not charging at all.

I now have a new 2019 MacBook Pro 16" which just arrived from Apple's factory in China. It has exactly the same defect. I have reset the T2 chip several times and reinstalled the OS several times, but the problem persists.

It's quite clear that the problem is not due to off-brand chargers or cables. It seems likely that there's a firmware bug here.

Apple will probably realize this and fix it in the future. Note that large corporations are very resistant to learning about problems with their products, so it will likely take many months and quite a few complaints before this comes to the attention of anybody at Apple with any decision-making authority.

What is your setup? What is connected to your Mac (you indicated a backup external drive, what model/make is that drive)? Is your power supply connected directly to the laptop, or does it go through an adaptor or a monitor? Are you going through a power strip or UPS? Is your AC power stable or reliable?

The reason I ask is that these things can all impact your situation.

Keep in mind that many thousands (maybe tens of thousands) of users are using these Macs and not experiencing a discharge down to 20% when using external drives or games. So something seems to be different about your situation or setup. It is possible that you have two defective Macs in a row, but the likelihood of that seems low. It can be like a detective hunt to track these things down, however, I believe you when you say this is happening.

I believe that the laptop with original cables and power supply should be able to handle the load. We have two of these 2019 Macbook Pro laptops and frequently use them to make "clones" from one external drive to another, in other words two external drives are connected and we are copying large (up to 4 TB) amounts of data from one external drive to the other over an extended time period of ~ hours. Also used in the manner you are, backing up from laptop to a different external drive (we use both mechanical spinning drives as well as SSDs). I have also done Time Machine backups of the laptop at the same time as "cloning" the drive, e.g. multiple drives connected and working all at once. On these units, I have never seen a discharge as you describe when plugged in.

Can you describe more precisely your setup? Are you using a different power supply and cable from the first unit that did not work properly?

Thanks for your interest!

My setup is as vanilla as possible. My first 2019 MacBook Pro 16" was was built-to-order by Apple in China and shipped directly to my house. I plugged the Apple-supplied charger into a 110V wall receptacle and used the Apple-supplied USB-C cable to connect the charger to the laptop. No other items were connected to the laptop. I don't use any external disk drives or other devices.

I did not make any oddball configurations to the MacBook power settings. It's set to sleep if on battery power, but to remain awake 24/7 when powered by the wall charger.

My laptop makes a nightly backup via WiFi to cloud storage. When I wake up in the morning, the computer would sometimes be asleep because it was running on battery and the state of charge was low.

Unplugging and reconnecting the USB-C cable would provoke the MacBook to start charging.

T2 chip resets and software reinstallations didn't improve charging reliability. Apple support recommended wholesale replacement, so I now have another 2019 MacBook Pro 16". This new computer is also plugged into its new Apple-supplied charger with its new Apple-supplied USB-C cable. It also has exactly the same charging problem.

I started designing motherboards and writing low-level firmware back in 1977, so I've helped debug a fair amount of problematic hardware during the past 40 years. This charging problem smells familiar to me. I suspect that there's a problem with the circuitry that handles USB-C power delivery or a firmware bug with the driver for this circuitry. I imagine that Apple will recognize the bug and fix it within the next 12 months or so. In the meantime, I'd like to find workarounds that will make my MacBook Pro adequately reliable.

Wow, well that's about as vanilla as a set up can really be, and all on original Apple equipment. It should have plenty of "margin" for charging and use of WiFi should not be an issue either, there's not much power needed to send on WiFi and lots of people are on WiFi all day long anyway. You should not have to do this on a new Mac, but have you tried resetting SMC and NVRAM? Otherwise, back to service request I guess, your new laptop sounds flawed like the previous one. HAs turning off the new Battery Management feature helped at all? I like that new feature on my laptop but it could have latent bugs that you have uncovered ...

sophieogle,

Have you seen my previous comment about the disabling Battery Health feature? Have you tried doing so?

This feature will drain your battery from 100% to 90-75% on the daily for "improving" battery health and sounds like what you're looking for.

Thanks for your suggestion. No, I haven't tried disabling Battery Health. I can imagine that bugs in that code could cause charging problems.

However, I've been doing some tests with the USB-C charging cable that came with my laptop. The test results make me more suspicious of USB-C cables and power management than the "Battery Health" feature.

I've been using the "System Information" app to monitor my power situation while the power adapter is plugged in to different USB-C ports on the laptop. The "AC Charger Information" section typically shows that my adapter is 94 watts. But the other morning I saw that it was showing that my adapter as 60 watts. Same adapter, same cable. Just a different day.

Although other folks have described how their USB-C cables are imprinted with identifying information, my cable has absolutely no markings whatsoever. This makes me wonder whether Apple has multiple suppliers for their USB-C cables, and a recent batch of cables has a defect that causes intermittent power delivery problems.

I've learned more about the problem.

I'll start with a reminder that all hardware described here was purchased new directly from Apple as a custom build.

When the charger is plugged in to the left rear USB-C port of my MacBook Pro, it is identified properly as a 94 watt charger. The MacBook Pro charges and operates as expected. I haven't seen any power management problems while using this port.

However, if the Apple charger is plugged in to the right rear USB-C port of my MacBook Pro, the MacBook sometimes identifies it as a 60-watt charger. When this happens, the MacBook has problems with power management. During periods of moderate use, the battery will start draining. This can continue until the state of charge goes so low that the MacBook puts itself to sleep. Even when applications are closed and the computer is idle (CPU use less than 3%), the MacBook may not attempt to charge the battery. When I unplug and reinsert the USB-C cable, the MacBook will start charging.

It's interesting to consider that I've seen this same behavior on two MacBook Pro 16" computers, both purchased directly from Apple within the past 60 days. Both had problems when power was supplied to the right rear USB-C port.