2020 MacBook Air - charging with USB-A to C cable

[segfaultdotorg]

Does anyone do this on a regular basis, and if so, can you comment on whether you experience the same issue? If I leave my Air plugged in to a 12w USB-A power source, usually for a long period like overnight, it often shuts completely down and restarts when I open it up. This occurs even when the battery was not low when I first plugged it in.

I know using a low wattage charger will cause it to charge more slowly, but I don't think it should just randomly restart itself because it doesn't like the charger I'm using.

I've tried different cables and different non-Apple chargers and plan to try using a 12w iPad charger and a 5w iPhone charger to see whether I experience the same behavior.

 

[magbarn]

Not saying what you're doing is completely wrong, but trying to charge a laptop with a 11+ volt battery with only a measly 5 volt input is asking for trouble. Your voltage regulators have to work much harder to boost up your 5 volt input to the 11 volts minimum that your MBA's battery requires to charge it. The stock charger puts in 20V, even the old Macbook 12's 29 watt charger put's out 14.5 volts. It's much easier for Vregs to buck voltage rather than boosting it.

There's nothing in Apple's literature that supports charging of any of their USB-C charged MacBooks with a USB-A to USB-C adapter cable.

Anyways, I used to get away with doing this on my Macbook 12 which uses lower voltage vs the MBA (14.5 vs 20 volts), but the last time I tried a USB-A to USB-C charger on my partner's 2017 MBP 15 it never charged so I gave up.

 

[ouimetnick]

Not saying what you're doing is completely wrong, but trying to charge a laptop with a 11+ volt battery with only a measly 5 volt input is asking for trouble. Your voltage regulators have to work much harder to boost up your 5 volt input to the 11 volts minimum that your MBA's battery requires to charge it. The stock charger puts in 20V, even the old Macbook 12's 29 watt charger put's out 14.5 volts. It's much easier for Vregs to buck voltage rather than boosting it.

There's nothing in Apple's literature that supports charging of any of their USB-C charged MacBooks with a USB-A to USB-C adapter cable.

Anyways, I used to get away with doing this on my Macbook 12 which uses lower voltage vs the MBA (14.5 vs 20 volts), but the last time I tried a USB-A to USB-C charger on my partner's 2017 MBP 15 it never charged so I gave up.

Voltage regulators work by providing a fixed/steady voltage. A voltage regulator can take a higher voltage and spit out a lower voltage at higher amperage but a voltage regulator can not put out a higher voltage than what it gets. I'm not sure why you are screwing around with this stuff. Use the USB C charger and cable that came with the computer!

 

[deeddawg]

In the past I too would use an Anker Powerline USB A to C cable to charge my rMB12 overnight when travelling.

Today though with USB-PD charging options so much more readily available, I'm not sure there's any point in trying to do this.

 

[segfaultdotorg]

Points well taken. My house is short on electrical outlets, so I have a giant 6-port USB-A charging tower in my living room. I read that the newer USB-C MacBooks can be charged from a USB-A portable power bank and was hopeful my existing charging tower might work.

I'll figure out a workaround, probably end up just getting a power strip to fit everything comfortably.

 

[magbarn]

Voltage regulators work by providing a fixed/steady voltage. A voltage regulator can take a higher voltage and spit out a lower voltage at higher amperage but a voltage regulator can not put out a higher voltage than what it gets. I'm not sure why you are screwing around with this stuff. Use the USB C charger and cable that came with the computer!

Modern DC voltage Regulators can both Boost/Buck the voltage. In other words they can boost or drop the voltage with a corresponding change in amperage of course. There's an efficiency cost for this when it comes to heat and power loss of course.

 

[jaytv111]

It really shouldn't shut down, unless it hits a low battery percentage and then it has to shut down. It sounds to me like it's not really charging and it's running down the battery overnight. Since it's a charging tower is it charging a bunch of things at the same time? Maybe it's dropping down from 12 watts to 5 watts (or even lower), which I think USB-C Macbooks reject less than 12 watts, and if they detect low voltage or current they'll stop charging. I haven't tried out this kind of charging myself though, I have a 15" Macbook Pro with USB-C and I only tested out to see if it charges over 12 watts or 5 watts, and it charges with 12 watts but never 5 watts, and I'm sure any voltage or current drop will make it stop charging too.
I would recommend of course using USB-PD only to charge Macbooks, never phone chargers unless an absolute emergency. You can now get multi-USB-C port chargers (I actually finally got my Hyperjuice GaN charger, it can deliver 100 watts to one device, or charge 4 devices at once at lower power levels, and my Macbook Pro reports it gets at least 30 watts with 4 devices connected, so it's always enough power with this charger to charge).

 

[deeddawg]

I'll figure out a workaround, probably end up just getting a power strip to fit everything comfortably.

As @jaytv111 mentions it probably shouldn't shut down but perhaps something else is going on.

Since I had an Anker Powerline USBA to C cable here I gave it a try with my MBA. Used to work great with my rMB12 to charge overnight and even slowly charge while in use. Looks like it's not going to charge the MBA with the lid open, though it might do something with it closed. Haven't tried it.

Probably going to be simplest to just get something like this, and the bonus is the Apple charger is then parallel to the wall: https://www.amazon.com/Adapter-Fosmon-3-Prong-Portable-Grounded/dp/B073X1K1R6

 

[segfaultdotorg]

It really shouldn't shut down, unless it hits a low battery percentage and then it has to shut down. It sounds to me like it's not really charging and it's running down the battery overnight. Since it's a charging tower is it charging a bunch of things at the same time? Maybe it's dropping down from 12 watts to 5 watts (or even lower), which I think USB-C Macbooks reject less than 12 watts...

Some of the shutdowns were starting with high battery charge states, and I'm always getting the "charging" chime when I plug into a USB-A device. I saw shutdowns when it was the only device plugged into the charger, as well as when I used a dedicated 12W charger with a USB-A to C cable.

The only thing I can speculate is that, for whatever reason, it wakes up when connected to the low-wattage charger and doesn't go back to sleep, stays awake, and discharges itself. There is no sleep control slider on the Energy Saver preference pane on this machine.

 

[segfaultdotorg]

Update: Just tried with a 12w Apple USB-A charger. Started charging at 71% battery capacity, when I opened it back up half an hour or so later, it was at 79%, but it had restarted. 🤬 Back to the factory charger, but I may pick up one of the really small 18w chargers and see whether it does the same thing.

 

[jaytv111]

So I tried a 12 watt charger on my 15 inch and left it for like 20 minutes. It said it was charging but it didn't go up 1% (started at 82% and left at 82%). Pretty pointless. But it did not reboot. Maybe if it was off it would actually charge. It does estimate over 10 hours to charge that 18%. It also stopped charging then started charging again, at least 2 times for the first few minutes (it just does not like using a 12 watt charger even though it technically can). Part of the problem is that the machine is probably gulping down that 12 watts in use and leaving nothing for the battery which is confusing the power subsystem.

 

[segfaultdotorg]

I've found that if I used the 5w or 12w charger while I was using it, the charge level would basically tread water and neither increase nor decrease (or decreased very slowly with the 5w charger). And it wouldn't randomly reboot while running.

Today's test - 18w Anker IQ3 USB-C charger with OEM Apple cable. This one is roughly the size of the 5w Apple charger that is included with non-Pro iPhones. Seems to charge well. No reboots so far, but not enough testing to decide a final verdict. It's possible that the voltage regulator on my Air can handle a 9V input but isn't strong enough to handle a 5V for a sustained period of time.

 

[segfaultdotorg]

The Anker IQ3 worked well for charging the MacBook, but didn't work well with my Fire HD10 (which has a USB-C connection but will only charge at 5V). The IQ3 claims it will charge at 2.4A at 5V, but I was only seeing 6-7 watts with the Fire tablet connected vs. 10 watts with a normal 2.4A 5V USB-A charger vs. 14 watts with the OE MacBook charger. So, I'm sending the Anker back. May pick up a 30W GaN charger at some point, since that should be equivalent to the OE Apple charger.