I have a 15" 2019 MBP and want to be able to charge it at work without carrying my adapter and cable back and forth. At work I have a Dell OptiPlex 7050 and two Dell monitors (one is HDMI, the other is VGA/DVI). Unfortunately, the way the office is set up I don't have easy access to an actual plug into a wall....

So far I've tried plugging my USB-C cable from my MBP to the Dell desktop. With that, the computer recognizes it's plugged into a power source (gets the little charging icon and says "Power source: Power adapter") but also states that the "Battery is not charging" and the percentage continues to drop. So that didn't work.

Are there any other suggestions?

Would be helpful to get input on a few things:

  • Is there a way to get the USB-C from the Dell desktop to work?

  • Would USB-A from the Dell desktop with a USB-A to USB-C cable work any better?

  • Do all computer monitors allow pass through charging? What would be the best way to go about trying this (HDMI? VGA? DVI? Or USB-A?)


Assuming that the monitors use an IEC plug on the backside, you can use an IEC cable splitter, like this


to grab the mains power from the monitor power cable and gain an extra power plug.

Then use an adapter like this


to convert the extra IEC plug to the power plug of your choice (this is a US NEMA plug, but these adapters are available for any power plug standard – UK, Euro, Schuko and whatnot).

Keep in mind that in many countries you have to ask you employer first if you want to charge external devices at work, otherwise it w/c/ould technically be stealing.

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  • 1
    I don't think most employers would be concerned about 'stealing electricity' but they might well be concerned about the security threat of connecting a personal device to a business computer via a data-capable connection such as USB. – nekomatic Aug 23 '19 at 15:30
  • This is not a question of concern but of legal requirements. I can only speak for Europe: Most employers obviously tolerate but you technically have to have permission. Btw. an IEC cable does not carry data, only power. – Gummibando Aug 23 '19 at 15:37
  • This gains you mains power, it still means you have to have a power supply & its attendant cable. – Tetsujin Aug 23 '19 at 17:38
  • And then what? The data from the computer transcends in a magical way via the USB-C PD cable and the power supply to the A/C line? – Gummibando Aug 23 '19 at 17:49

The USB ports in the Desktop and monitors don't provide enough power to charge your MacBook. These ports tend to be build "to spec", meaning they output only about 500mA (USB 2.0) or 900mA (USB 3.0). Sometimes PCs have dedicated charging ports (maybe colored yellow) which provide more than 1A (they exceed the official USB specs), but that's still not nearly enough to charge a laptop. [1]

So you will need to get a charger (or a hub/dock[2]) that supports the "power delivery" (PD) protocol.

You can get them from anywhere between 18 and 100 Watts, and the power output makes a big difference in how fast your MacBook will charge. If you have patience, especially if you're not using the computer while it's charging, you can get away with a lower power (and smaller!) adapter (I use a 56W one, I would not recommend going lower than about 45W). Companies like Anker, Aukey, RavPower make some that are much cheaper and more compact than the original Apple charger.

[1]: The power delivery protocol allows the power supply to step up the voltage in order to provide more power at a reasonable current. The Apple 61W charger goes up to about 3A at 21V (the equivalent of 12.2A at 5V, or 24 times as much current as a USB 2.0 port can provide).

[2]: Note that some of the USB PD compatible hubs need a USB-C PD input in order to provide power on the output, so your best bet is to get a USB-C charger with Power Delivery and skip the hub. The ones that don't need a PD input tend to be (expensive) docks with lots of different ports.

Here are Apple's recommendations for how much power your charger should have: https://support.apple.com/en-us/HT201700

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  • So this would be a USB-A or USB-C device that I plug into the desktop computer but then also needs a separate power source (a wall plug) to increase the power output to make it enough for the MBP? Is that right? – Jon Aug 23 '19 at 15:18
  • @Jon No, you would only plug it into the wall and the MacBook. Here's the one I use. – Stefano Palazzo Aug 23 '19 at 18:58

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