Why is my (genuine Apple) 10W/2.1A iPad AC charger providing only 5W when powering my new M1 MacBook? [closed]

Solution 1:

Why may a (genuine Apple) 10W/2.1A iPad AC charger† not adequately power an M1 MacBook?

There are so many reasons and caveats!

1. Because the Mac can pull more than 5 watts (the default/old USB standard) only from a modern USB power supply that supports "USB Power Delivery", A.K.A. USB-PD. (And most tasks will need a little or a lot more power than this.) Why? The M1 MacBooks do not speak the proprietary signal protocol older Apple kit uses to support 10 watts over USB. The M1 MacBook doesn't try to use the old protocol to signal to the power supply that it wants 10 watts, so it only gets 5.

2. Newer (than iPhone 7, genuine Apple) iPhone and iPad AC chargers tend to support USB-PD, and thus can send their nameplate power to an M1 MacBook. Again, older ones do not. (specs: Apple iPad 10W USB Power Adapter )

3. Lower watt USB power adapters that support USB-PD are becoming more common over time. A USB power adapter that doesn't support USB-PD might supply enough power to slow the discharge from the battery to a standstill if the Mac is doing very little, but it is more likely to discharge than charge to the battery. (I have seen both happen.) After connecting a 10 watt USB power adapter to my M1 MacBook Air, it will show as charging in System Preferences but simultaneously (yes, with a refresh) show as not charging in System Information. The battery of a MacBook under heavy load, may discharge even when supplied by a 15 or 20 watt adapter.

4. UPDATE: YMMV indeed! 2 days later, I accidentally discovered that with the same charger and Mac, but a counterfeit Apple cable (it came with AirPod Pros that were also counterfeit but in a real Apple box) instead of the Baseus cable used above, and connected thru a USB power meter, the Mac shows as charging in System Preferences and per System Information, which says it's being delivered 8 Watts. (7.1 Watts per the USB power meter). </me throws up hands!> I had thought the Baseus cable would be of good quality, but it seems I was mistaken. And either this old 10W Apple charger supports USB-PD, or the M1 supports the Apple-proprietary protocol. This proves the following point! =>

More (real-world) caveats. 4. If you have a cheap (in both senses of the word) USB cable, it could well be only a 2-wire cable, so the data lines that are used to negotiate Apple's proprietary USB power protocol, as well as USB-BD, won't work.

1. I have noticed that significantly more power can be pulled over shorter USB cables at 5V than over longer cables (e.g. 2.1A over 6"(~15cm), as low as 1.2A over a (non-defective) 6'(~180cm)).

2. Similarly, if there's a bad data line connection, only 5W will be supplied.

3. Also, a device with a Li-ion battery that's almost full (>~80%) will not charge it quickly, as this damages it, so don't let this mislead you.

4. Apple says, "If your Mac uses USB-C to charge, you can charge your Mac notebook with any USB-C power adapter or display. For the best charging experience, you should use the power adapter and cable included with your Mac notebook."2 But I suggest not being unnecessarily adventurous about the chargers or cables you use with an M1 due to the reports I've heard. On the other hand, I've not entirely followed this advice and so far so good:

   a. using an Apple 10W charger with Power Delivery, as noted above, depending on usage, one can get away with a tiny power adapter for a traveling M1 MacBook.

   b. using a eero/Google, I get 15 watts and the battery does charge if I'm just doing what I'm doing now.

   c. I later found a knock-off of Apple's 10W charger, but I'm going to take my advice and not try to plug my M1 into it. - 2nd UPDATE!

5. See Apple's "About Apple USB power adapters" (and the less informative "About Mac power adapters", AKA "Find the right power adapter and cable for your Mac notebook.") for more info.

6. I suggest you believe Apple when they say their power supplies are safer. Trust me or search for "Bunnie" Huang and other's teardowns, e.g. on YouTube and do a bunch of research to see how dangerous some can be. Not chabuduo at all. Cheap ones often fail, and good (e.g. UL certified) ones are designed so that when they fail, they don't fail catastrophically (cause a fire). Much lower cost with lower reliability parts can work, but only if the design still follows safety principles.

(Some content from " Other than speed, is there a reason that a 10W iPad charger shouldn't charge a new MacBook Pro 2016? ")

†Or 'brick', but that term hasn't make sense since the old school adapters built around a transformer consisting of a metal, brick-heavy core wound with copper wire were made largely illegal. Such adapters are often called vampires because they suck the same amount of power whether the device they're powering needs it or not; solid state devices made this inefficiency needless and is why they were made largely illegal. So many other names. Power supply. A/C adapter. etc. [edit me]