What I'm Doing

I have a laptop and I am looking to get a portable screen for my laptop.

My Problem

Some of them have separate video and power connectors, but others give power and video over a single USB 3.0 cable. I really don't want to power a second monitor from my laptop, because that will really drain my laptop's battery. Instead I would like to power it from a battery pack.

Product / Hardware Recommendation Needed

I was thinking that some sort of USB Y shaped cable would do the trick. Then I could plug it from my laptop (male data) AND batterypack/wall (male power) TO my portable monitor (data + power)

  • The USB 3.0 standard only guarantees 900mA of current on a single port, so a portable display is only going to use a maximum of 4.5W if it is USB 3.0 compliant. Depending on your laptop (battery, CPU, and storage specs) it may not be a significant cost to your battery life.
    – Romen
    Jun 5, 2019 at 21:08

2 Answers 2


A quite experimental solution would be a DIY one (see below), but you will need some experience and maybe even some luck. As a less experimental solution I suggest you to use an USB hub with an extra power input.


DIY possibilities (experimental / ”danger zone“)

I highly suspect those DIY ways not to work with all USB devices.


I found one on Amazon, USB 2.0


This is a USB 3.0 cable


It uses the power of both connectors to power the female connector.

  • This specific cable will not work for a USB 3.0 monitor.
    – Romen
    Jun 5, 2019 at 21:01
  • I added a USB 3.0 variant :)
    – Houbie
    Jun 5, 2019 at 21:55
  • 1
    Even that one is possibly no good, it's designed to receive power from both USB ports (which are female for some reason) and this would mean the laptop battery is still giving power to the portable display. Maybe there's a way to limit or disable the laptop's power output though...
    – Romen
    Jun 6, 2019 at 14:56
  • 1
    I highly suggest not to use such Y cables with two different sources, only with one source, e.g. a PC. Otherwise you'd be connecting two +5V power sources with the cable. Even both item descriptions say: ”link 1 USB device into 2 USB Ports on your PC for more power
    – myrdd
    Jun 10, 2019 at 20:15

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