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I have a 2015 MacBook Pro with a MagSafe 2 charging cable. My wife has a new MacBook Pro from 2016 with USB-C. I was wondering whether I could technically (in the matter of electronic feasability) use her charging cable on my MacBook and vice versa with some sort of adapter / dongle, and, if so, where I would get one?

  • Is the focus of the question on "is it electrically feasible" or on "where to I get an adapter"? The second one would be off-topic, please edit your question to indicate what you are looking for. – nohillside Feb 25 '18 at 19:25
  • I'm trying to figure out the same. I've found these two options so far but not sure if they are reliable: ebay.co.uk/itm/… ebay.co.uk/itm/163153641220 – szerte Feb 28 at 0:30
  • @szerte Sadly, they don't seem to be compatible with USB-C powerbanks, which is what I'm after. – Agent_L Apr 13 at 17:09
  • I can confirm both of the above works. More detail : discussions.apple.com/thread/… – szerte Apr 14 at 21:52
  • amazon.com/dp/B07G95NSC9 does what you want (with the extra magsafe 1->2 passive adapter from Apple). Who knows how safe it is, of course. – Rehan Khwaja Jul 11 at 23:22
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You don't want to mix those two.

Why?

Because the USB-C port conforms to the USB 3.1 Power Delivery Specification whereas the Magsafe charger does not. Part of that specification includes the negotiation of delivered power. The Magsafe will not negotiate how much power is supplied. What it's looking for is the presence of the 1 wire charging circuit before it begins charging.

There may be adapters/converters on the market that will convert one interface to the other and vice versa, but (IMO) those cheap adapters are not worth the risk of sending the wrong voltage to your very expensive MacBook Pro.

Bottom line, use the genuine adapters built and designed for your MacBook Pro.

  • 1
    If that "cheap adapter" didn't actually act as a step-up/step-down converter to the voltage it negotiated with the MBP, I'm hard-pressed to see how it would work at all. – Charles Duffy Feb 24 '18 at 16:58
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    @CharlesDuffy: There are some amazingly bad USB-C products on the market. – Kevin Feb 24 '18 at 16:59
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    @DanEllis Computers will draw as much current as it needs, but the USB-C standard can provide multiple voltages. If the wrong voltage gets to your computer, it's bad. Also, the USB-C standard negotiates the maximum power (current) the computer can draw, if it tries to draw too much, you'll fry the supply. With the MagSafe adapter, the computer doesn't know how much is too much. – jkd Feb 24 '18 at 19:47
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    @Alexander They probably do. Allan is just saying that he won't trust the cheap adapter to protect his expensive MacBook. Also, that doesn't protect against the computer overdrawing. – jkd Feb 25 '18 at 3:59
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    USB PD is a bit of a standard, and you can buy perfectly good third party adaptors that won't blow up your system – Journeyman Geek Feb 25 '18 at 7:39
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The ElecJet Anywatt One fills this need, for the purpose of powering a USB-C device from a MagSafe power supply.

From the product page:

Anywatt built-in self-developed LDR6032 smart chip supports the latest USB C Power Delivery & PPS protocol, Automatically recognize the end device needed power and adapt the voltage and current to best suit the end device charging purpose, range from 5V@3A 9V@3A 12V@3A 15V@3A 20V@2.25A and PPS 3-12V@3A MAX.

It is not licensed by Apple. That said, I own one and have been using it without incident to connect my 2016 MacBook Pro (87W) to my Thunderbolt Display; it can't provide the full 87W, so the battery charges somewhat more slowly than it would if I had the big charger with me, but it's been fully adequate in practice.

  • Well, it costs $24 while the same site sells complete mains charger for $25. So the adapter is rather limited to niche applications, eg when you can't plug in your charger, but the place provides MagSafe cables. – Agent_L Feb 25 '18 at 10:47
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    @Agent_L, yup. In my case, I have a Thunderbolt Display in storage at my coworking space -- with the AnyWatt, I only need the one plug (out of three per shared desk) for both monitor and laptop, as the monitor provides MagSafe output; with a separate adapter, I'm using 2/3, limiting whoever is on the other side of said desk to one. – Charles Duffy Feb 25 '18 at 17:30
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You can buy adapters (dongle) that converts USC-C PD signals to Magsafe1 and 2 (and in fact to any needed voltage to any old laptop). There also the inverse adapters that converts from a Magsafe 1 or 2 chargers to USB-C output to charge a modern computer although less useful.

The irrational claims of how a computer or a charger could be fried is just a old wives fable. You cannot over draw current for a USB-C PD charger because it will shut down. The charger cannot provide more than its design capacity nor provide more current than the load needs!

The reverse of charger providing "too much" of something or another that could fry a computer is also untrue. No computer use the direct charger input for operating the computer or charging the battery. The voltage is regulated by a DC-DC converter to generate the needed voltages. If the provided voltage too low, it will not charger; if the voltage is too high, the charging circuit will shut down.

  • Hm, thanks for your thoughts. I'm not really down to testing this with my Mac, though, ha! Sorry! – LinusGeffarth Jul 19 '18 at 6:47
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    Like the irrational claims of a Google engineer who actually bricked his Pixel with a faulty USB-C cable? Not only did the cable kill the analyser, though, but it also fried both USB Type-C ports on Leung's Chromebook Pixel: "Neither would charge or act as a host when I plugged in a USB device such as an ethernet adapter." Upon further analysis, Leung found that the cable had killed the Chromebook's embedded controller arstechnica.com/gadgets/2016/02/… – clacke Jan 24 at 3:29
  • Maybe it shouldn't be possible, and ports should be buffered against faulty inputs. In practice though, apparently you can fry computers and possibly power supplies too, if you give them inputs the manufacturer didn't account for. – clacke Jan 24 at 3:30
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    @clacke That's mostly irrelevant. The concern here is whether the laptop might draw too much current from the charger. The cable in Benson's review had the polarity of the positive and negative voltage lines swapped; protecting against swapped power rails would require a different type of protection circuit than overcurrent protection would. Also, note that he didn't say that it damaged the power supply! :) Personally, I would avoid trying to charge the laptop from another computer, but a dedicated charger should be fine. – dlitz Feb 9 at 21:47
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    @clacke That's not what was being claimed at all. – rspeed Feb 23 at 1:20
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Electrically, it is possible to go from either direction, it just requires a computer (microprocessor, etc) in between to do the USB-C PD negotiation. As people have noted, there are plenty of MagSafe2 → USB-C PD options.

There are only 3 wattages for MagSafe2[1] chargers and they have well known voltage / currents. The MacBook knows what the max wattage for the charger is by getting the id of the charger from the MagSafe2 plug itself. It won't draw more current than the charger will allow because it knows which charger is plugged in. Any USB-C → MagSafe2 dongle would essentially ensure the wattage via USB is available and emulate the correct MagSafe2 charger ID.

There does not seem to be a USB-C PD → MagSafe2 option, possibly because it would require a charger that supports enough wattage to both power the MacBook (45W/65W/80W) and the dongle itself. So at a minimum, ~50W to supply 45W (which is only enough for a MBAir and not enough for a Pro).

[1] http://www.righto.com/2013/06/teardown-and-exploration-of-magsafe.html

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As others have said, the standards being different makes this kind of dangerous if you're not careful what you're buying.

But if you only want the magnetic connector (so that it doesn't pull the laptop with it when tripped and such, you could try one of these options to convert the USB-C connector to a magnetic one.

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