Add External Power To Any USB Hub

[Andrew] was getting some poor performance from a couple of USB devices he had connected through an unpowered hub. This is a problem because the hub prevents devices from negotiating with the host controller for more current. He fixed it by adding an external power supply to his USB hub.

In this case the PCB already had a footprint for a power connector. The manufacturer uses one board for several different models and just leaves the supply components unpopulated. [Andrew] managed to find a barrel jack in his parts bin that matched the footprint.

One important thing to do before hooking up the source is to disconnect the 5v wire from the incoming cable from the computer. The other tip we can give you is to use a good regulated 5v source to ensure you don’t damage the stuff you’re trying to power. That means avoiding deals that are too good to be true.

38 thoughts on “Add External Power To Any USB Hub

  1. been there, done that. although I added a line from the power to go to the computer end. I did this so I could power the cheapo tablet while it was OTG’ing the hub when I had USB memory, mouse and keyboard connected.

      1. The one in the OP I see at the dollar store. There was another version that was a bar form factor there before… I popped one open to re-purpose it, and to my surprise there was no circuitry, none- All ports were tied parallel to the input cable! That would explain why it was so flaky with more than one device, but it worked to my advantage. I was turning it into a multi-port USB charging-only brick, so all I needed to do was add 2 resistors!

        Is that part of a USB spec to allow shared bus w/o a routing/delegation IC?

        1. No, at least low high and full speed detection would no longer work as both lines would be pulled up. The signal integrity would also be ruined even if the data lines were not connected in the other devices connected to the ‘hub’

    1. No doubt in my mind it would have been the wall-wart or power supply that caused the fire. Not he actual hub itself.

      Got to watch that cheap stuff off eBay and the like. Do you know whether the item you are buying is not rejected stock? Willing to bet your house on it?

      My rules is that if i’m going to plug it into the mains I’ll buy from a reputable supplier. For the rest, it would be unlikely for low voltage (ELV) electronics to cause a fire at a low current capacity.

  2. The DC power jacks I use have three legs. The post is always connected to the positive output, and the negative is shorted to the third pin when there’s no barrel plug inserted. So when you have an external supply connected, it runs off that, but with no barrel plug, it can run off another source (presumably battery, or in this case, the 5V line from the usb cable). From the photos, it appears that the replacement jack had a similar construction. In other words, desoldering the 5V line wasn’t necessary.

        1. I’m a bit late to the party –
          The foward voltage drop on most diodes is too much to still power devices with no plug-pack. IN4007 or IN914 looses 0.5 – 0.6 volts, any processor or chip that uses +5V vcc will complain by doing random weird things if vcc is any less than +4.8V
          BAT85 only have fwd bias voltage of 0.2V but are so stretchy that more than a tiny bit of current makes fwd bias volts increase.

  3. Simplest way to add external power supply with USB hub is using USB Power injector… It’s very simple to DIY or you can even buy it – eg. here:

    If you connect it between hub and powered device it will work for sure. It should also work when connected between computer and hub, but you should get proper power brick (approx. 2A for 4 devices) also hub shouldn’t have any additional active power stabilization circuitry (but that is very unlikely and as i checked mine hub, it just directly connects all power rails together)

        1. If the device properly negotiates to use more than 100 mA, such an injector will change nothing. The hub/host will reply “no more power available” and the device will refuse to charge/work.

          1. IMHO not in all cases… It may be true for devices like cellphones and others that are negotiating. But i don’t need to charge cellphone using such hub… Not every device asks for power… some of them will just drag the current they need… eg.: external disk drives sometimes lack current and they just fail with clicking sound of parking head in middle of operation…

    1. …and the reason he is using USB hub is because he has a second usb port free. I think using third and fourth usb connection, so that you can power all 4 devices connected to the hub in 100% is even better idea… Yeah, that’s surely the main purpose of any USB hub.

  4. any USB hub? thats a bit of a stretch
    and keep in mind that you should plug in a REGULATED power suply .. not a 5v generac wall wart … this cheepo hub more than likley does not have an LDO regulator built in so you may want to cut the trace and put one in or risk frying things that do not like more than the set USB power tolerance of ~+/- 5% from 5V

  5. “If the device properly negotiates to use more than 100 mA, such an injector will change nothing. The hub/host will reply “no more power available” and the device will refuse to charge/work”

    I’ve found this to be true with a low power hub (cherry USB keyboard – has 2 hidden USB hub ports covered up, the keyboard was bad from liquid spilled into it, so I scrapped it and use it only as a 2-port hub. this hub refuses any device over 100ma

    but another hub like the OP’s, works fine – I simply soldered an extension wire to an external power supply (wall wart with 5 v regulator)

    so how useful this is, depends on the hub not being low power

    the fake hub with all the ports tied together badly violates the USB standards. I’d be surprised if any 2 devices would work like that. I use hubs as extenders, so the fake hub would be useless.

  6. male to male cables violate the USB spec, good hubs have current measuring shunts on each output, notice I said output.. Supplying power in via a power out socket will not allow the hub to sense and react to overcurrent or faults not to mention occupy one of the ports. If you disassemble a hub you’ll find a pad or tiepoint for external power in, then see how this power is routed through 1 or more shunts to the output ports. Unpowered hubs jumper this to the input port and draw all power through it. Most of the time it won’t make any difference but critical loads like USB powered HDD’s may fail with that arrangement. Many USB chargers don’t actually produce the power quantity or quality that actual USB loads require. It would need to be rated at over 2.A (assuming 4-port hub) and have good regulation. This is a power supply, not just a charger. Using a charger in it’s place risks problems and damage.. Chargers are often poorly regulated & weak.

    1. Most units that require more power have a double ended USB connection with male/male ends therefore the power supply can plug into the said unit direct or via a male/female cable so no spare socket is used. Most chargers are power supplies. and found to be pretty well regulated. I have used this format for around 8 years and never had a problem with portable b-d players, hard drives etc. Anything can fail, even home made stuff.


    “each end of a USB cable uses a different kind of connector; an A-type or a B-type. This kind of design was chosen to prevent electrical overloads and damaged equipment, as only the A-type socket provides power. There are cables with A-type connectors on both ends, but they should be used carefully.”

    “though not that common, A-A cables are used to connect USB devices with an A-style Female port to a PC or another USB device, and for data transfer between two computer systems. Note: Typically an A-A cable is not intended to connect two computers together or to connect a USB hub between two computers. Doing so may cause irreparable damage to your computers and may even present a fire hazard.”

    What you personally have gotten away with and what advice should be given to uncounted random people who may not be as lucky or as smart as you, are 2 different things.

    I studied the standard closely while making my own custom cables out of foam coax in twisted pairs, but the average person will find the cable rare, that will allow him to plug 2 powered hosts/hubs in together due to the dangers cited in the links provided.

    Most motherboards have polyswitch protectors, some have fuses, but a few have no protection at all, I’ve seen USB cables fry and smolder.

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