You forgot your MacBook charger, but you do have a USB-C phone charger or a power bank. Can you charge your MacBook with a phone charger? Often yes, but very slowly, and sometimes only when the MacBook is off or asleep. This article explains what happens with a weak charger, which power banks are suitable and what to watch for.
Blue Apple repairs MacBooks in Amsterdam, including charging ports and charging problems.
How does USB-C charging work?
MacBooks with USB-C charge via USB Power Delivery (USB-PD). The charger and MacBook agree how much power is delivered. A charger that can do less than the MacBook asks simply delivers what it can. The MacBook then charges more slowly. That is safe, as long as charger and cable are of good quality.
With a phone charger
- 20 watts or less (a normal iPhone charger): the MacBook only charges noticeably when off or asleep. During use it often drains slowly.
- 25 to 45 watts (fast phone chargers): a MacBook Air charges reasonably with these, especially for light work. A MacBook Pro charges slowly.
- macOS may say a low-power charger is connected. That is a warning, not a fault.
If your MacBook only charges when off, read MacBook only charges when it is off.
With a power bank
A power bank only works if it has a USB-C output with Power Delivery. Note:
- Wattage: 45 watts or more for a MacBook Air, 65 to 100 watts for a MacBook Pro.
- Capacity: a 20,000 mAh power bank tops up a MacBook Air about once, less for a large MacBook Pro.
- Flying: power banks up to 100 Wh are usually allowed in hand luggage, not in checked luggage.
How long does charging take with a small charger?
A MacBook Air with a battery of about 50 Wh needs well over three hours to fill up with a 20 watt charger while switched off; in practice longer, because the last part goes more slowly. During use it is a matter of keeping up: with light work such as e-mail and writing that sometimes just works, with video or many tabs it does not. A 30 to 35 watt charger already makes a big difference for a MacBook Air. For a large MacBook Pro even that is really too little to charge during heavy work.
Old MacBooks with MagSafe 1 or 2
Older MacBooks from before 2016 have no USB-C. You charge them only with a MagSafe charger. A phone charger or normal power bank does not work there without a special adapter.
What to watch for
- Cable: use a USB-C to USB-C cable. A USB-A to USB-C cable delivers too little.
- Quality: cheap uncertified chargers can overheat or damage your port.
- Heat: do not leave charger and MacBook under a blanket or in the sun while charging.
Choosing a spare charger
If you want a second charger for travel, choose a USB-C charger from a known brand with at least the wattage of your original charger. Small GaN chargers are light and can often charge your phone at the same time. See which charger fits my MacBook and MagSafe 3 or USB-C.
Charging does not work at all
If your MacBook charges with no charger at all, not even the original, the charging port, battery or charging section on the logic board may be faulty. See USB-C port not working and MacBook not charging.
What we do at Blue Apple in Amsterdam
We test your charger, cable and charging port, measure the charging and replace what is broken. You hear beforehand what it costs. More on our page about MacBook charging port repair.
Frequently asked questions
Can a phone charger damage my MacBook?
A good charger cannot; it just charges more slowly. A bad uncertified charger can cause problems.
Can I use my MacBook charger for my phone?
Yes. The phone only takes what it can handle.
How do I see how many watts come in?
In System Information, Power, under the AC charger information.
