I took delivery of a 2021 14" MBP earlier this week (loving it) and in preparation I'd also bought a new LG 4k monitor. The monitor has USB-C and when connected 'powers' the MacBook/charges the battery. My question is whether or not this is harmful to the battery - i.e. not using the 67W Apple charger and the battery effectively being at 100% most of the time as a result.

It'll be fine. However, speed will depend on how much power is delivered from the monitor.

blythy said:

I took delivery of a 2021 14" MBP earlier this week (loving it) and in preparation I'd also bought a new LG 4k monitor. The monitor has USB-C and when connected 'powers' the MacBook/charges the battery. My question is whether or not this is harmful to the battery - i.e. not using the 67W Apple charger and the battery effectively being at 100% most of the time as a result.

100% not harmful.
Depending on how much power the monitor puts out, it may charge faster or slower than Apple's 67w brick. Most likely the monitor puts out at least 65w, so you'll likely see no difference at all.

As for the battery being at 100% constantly, there are some that believe this is an issue. I use a little app called Al Dente to limit the battery to 80% charge since mine is plugged in most of the time as well. When I need 100%, I can top it off on demand, though to be honest, 80% of a charge on the go still provides more power than I typically need.

Like others said, it will be fine.

If you are leaving it plugged in like that a lot, it is a good idea to turn on Optimize battery charging so the battery is not sitting at 100% all the time.

Weaselboy said:

Like others said, it will be fine.

If you are leaving it plugged in like that a lot, it is a good idea to turn on Optimize battery charging to the battery is not sitting at 100% all the time.

View attachment 2036692

Does that actually work? So that it will actually stay at 80% charge level, and so that it will also return to it after you occasionally use it as a laptop on battery?

Also is it possible to bypass monitor USB-C PD power when you also connect Apple MacBook original power supply at the same time? I very much like to avoid my LG monitor USB-C PD 60W power feed for many reasons and I was hoping MBP 14" included 67W Magsafe charger would do so that it would then only take power from it instead?

0906742 said:

Does that actually work? So that it will actually stay at 80% charge level, and so that it will also return to it after you occasionally use it as a laptop on battery?

It works for me. Here is a screenshot I just took.



What I have noticed is if you use it on battery it resets the charging algorithm and charges back to 100% for a few days. Then it seems to realize you are not running on battery and allows the charge to drift down to around 80% again.

So if you are say using it on battery every two days, it will keep it up at 100%

0906742 said:

Also is it possible to bypass monitor USB-C PD power when you also connect Apple MacBook original power supply at the same time? I very much like to avoid my LG monitor USB-C PD 60W power feed for many reasons and I was hoping MBP 14" included 67W Magsafe charger would do so that it would then only take power from it instead?

I have never tested this, so I don't know what it would do.

Weaselboy said:

It works for me. Here is a screenshot I just took.

View attachment 2036700

What I have noticed is if you use it on battery it resets the charging algorithm and charges back to 100% for a few days. Then it seems to realize you are not running on battery and allows the charge to drift down to around 80% again.

So if you are say using it on battery every two days, it will keep it up at 100%


I have never tested this, so I don't know what it would do.

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I didn't know that was a thing.

jav6454 said:

I didn't know that was a thing.

I think that came out with Big Sur.

Thanks everyone, helpful + reassuring

0906742 said:

Also is it possible to bypass monitor USB-C PD power when you also connect Apple MacBook original power supply at the same time? I very much like to avoid my LG monitor USB-C PD 60W power feed for many reasons and I was hoping MBP 14" included 67W Magsafe charger would do so that it would then only take power from it instead?

Some monitors will have a function to disable power, some will not.
However, the MacBook will only use power from one device at a time, so you can't damage it by plugging in the monitor and the MagSafe at the same time. It should automatically use the one providing more power and disregard the other.
That said, 60w should be more than enough to manage the 14" MBP, even with it running with CPU and GPU pegged to 100%.

In the optimized setting, it will cap the battery charge to 80% if you leave it on AC power regularly. Apple's worked pretty hard to help with battery longevity, minimize the bulging battery problem and provide convenience for customers.

xraydoc said:

Some monitors will have a function to disable power, some will not.

Mine does not.

However, the MacBook will only use power from one device at a time, so you can't damage it by plugging in the monitor and the MagSafe at the same time. It should automatically use the one providing more power and disregard the other.
That said, 60w should be more than enough to manage the 14" MBP, even with it running with CPU and GPU pegged to 100%.

Good to hear it should select higher wattage power source if both are connected. I definitely want to bypass LG monitor power feed and make sure I feed clean power from Apple provided power supply. I want to avoid possible issues with ripple voltage from third party power supplies.

0906742 said:

I definitely want to bypass LG monitor power feed and make sure I feed clean power from Apple provided power supply. I want to avoid possible issues with ripple voltage from third party power supplies.

I know that you don't want anything to happen to your new baby. I totally understand that. However, there's virtually no worry about the monitor damaging your Mac. I think I've plugged my MBP into the included power brick exactly once.

Yeah I think LG can be trusted I use the built in power on my thunderbolt 4 monitor and thats a Lenovo. No Problems there at all.

xraydoc said:

I know that you don't want anything to happen to your new baby. I totally understand that. However, there's virtually no worry about the monitor damaging your Mac. I think I've plugged my MBP into the included power brick exactly once.

robotica said:

Yeah I think LG can be trusted I use the built in power on my thunderbolt 4 monitor and thats a Lenovo. No Problems there at all.

I'd still rather use Apple incluced PSU, especially since it comes with the Magsafe connector, it is not much extra work to plug that in too. I was just trying to make sure this way it really then uses power from Apple PSU in my case where Apple PSU is 67W that comes with MBP 14" base model instead of my LG monitor USB-C PD 60W.

I have very little trust with other power supplies. There is always possibility for bad or deteriorating filtering causing them to output ripple voltage that is lethal for batteries. I have good memory of my one of my UPS backup power from few years back, one day battery started bulging and releasing toxic gas, luckily I was home at the moment and I was able to throw out that soon enough. Afterwards I was investigating issue with this product support and I could tell them that I have been monitoring UPS that it reports charging voltage and battery voltage well within normal range, I even measured both afterwards with multimeter myself. Then support told me that problem is due to ripple voltage, where using DC measurement, all looks allright but ripple voltage (AC in DC) voltage has increased due to failing capacitors and causing all these issues, so it kinda wear out battery and causing overcharging that charging circuit cannot detect.
Anyway, long story short, this company handled my case very well and compensated me with brand new device even my old was out of warranty already. besides this I have seen number of cases myself where similarly failing power supply has caused all kinds of issues with home electronics.

0906742 said:

I'd still rather use Apple incluced PSU, especially since it comes with the Magsafe connector, it is not much extra work to plug that in too. I was just trying to make sure this way it really then uses power from Apple PSU in my case where Apple PSU is 67W that comes with MBP 14" base model instead of my LG monitor USB-C PD 60W.

I have very little trust with other power supplies. There is always possibility for bad or deteriorating filtering causing them to output ripple voltage that is lethal for batteries. I have good memory of my one of my UPS backup power from few years back, one day battery started bulging and releasing toxic gas, luckily I was home at the moment and I was able to throw out that soon enough. Afterwards I was investigating issue with this product support and I could tell them that I have been monitoring UPS that it reports charging voltage and battery voltage well within normal range, I even measured both afterwards with multimeter myself. Then support told me that problem is due to ripple voltage, where using DC measurement, all looks allright but ripple voltage (AC in DC) voltage has increased due to failing capacitors and causing all these issues, so it kinda wear out battery and causing overcharging that charging circuit cannot detect.
Anyway, long story short, this company handled my case very well and compensated me with brand new device even my old was out of warranty already. besides this I have seen number of cases myself where similarly failing power supply has caused all kinds of issues with home electronics.

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You do you 👍🏼

xraydoc said:

You do you 👍🏼

I have used Anker chargers for about ten years (USB-A and USB-C) and have not had any problems with them and they seem to be a fairly trusted brand and feel quite comfortable with them. I'm sure that there are other popular brands that are fine. Apple is fairly limited in their product lines and sometimes you want a somewhat different or more flexible product.

My LG Ultrafine 27" 5K charges fine the 16" MBP.

fehhkk said:

My LG Ultrafine 27" 5K charges fine the 16" MBP.

That, too, is an excellent point. Same thing for me with the Dell Ultrasharp U2720Q. I've not heard of problems with the other Dell USBC monitors either. One class of vendors I avoid is the Chinese brands with the funny names. They might be perfectly fine but I just go with brands that I trust.

fehhkk said:

My LG Ultrafine 27" 5K charges fine the 16" MBP.

The real problem is that they all surely will charge fine seemingly. Just like the UPS backup power I mentioned above, it is just the day when your battery is boiling, you realize it was not fine even it works fine. Possible ripple voltage does not mean it does not charge the battery.

0906742 said:

The real problem is that they all surely will charge fine seemingly. Just like the UPS backup power I mentioned above, it is just the day when your battery is boiling, you realize it was not fine even it works fine. Possible ripple voltage does not mean it does not charge the battery.

Macs have been USB-C for many years now and I would expect that we'd have seen reports if there were issues with USB-C charging. There were problems with MacBooks no longer taking a charge, port issues and maybe circuit issues but Apple, and the industry, has had a long time to work out the bugs.

If there is a problem with the battery, just replace it. A battery replacement is $200 vs $3,000 device.

The only time I had issues charging my prior 2019 16" was when the CPU was running hot processing images and gaming. Haven't pushed the 2021 yet to see.

pshufd said:

Macs have been USB-C for many years now and I would expect that we'd have seen reports if there were issues with USB-C charging. There were problems with MacBooks no longer taking a charge, port issues and maybe circuit issues but Apple, and the industry, has had a long time to work out the bugs.

If there is a problem with the battery, just replace it. A battery replacement is $200 vs $3,000 device.

You did not get what I meant. It has nothing to do with USB-C.

Been using monitors to charge my Macs at 65w.. Since the 2017 MacBooks Pro! So don't worry about it, will work just fine.