usb - Can Current Backflow from Powered Hub's Adapter & cause PC Damage?

08
2014-07
  • SuperUserMan

    Getting this short:

    Can current flow from a powered USB hub's power adapter (lying 10 Meter away) back to computer via usb port and cause damage to Computer components like mobo, etc? What should be my concerns?

    Using a 2 Amp 5V Power adapter to power a 10m Long Active Repeater USB extension cable with 4 port HUB & plugging into PC's Front port, causes the following, after PC is shut down (bit scary)

    • PC Chassis fan to keep running (thought slower than regular speed)
    • Front Chassis HDD & power LED to turn on (though bit dim)
    • may be other things which i cant detect/see at chip level, in motherboard??

    More detail (in case U want to ask):

    To run 4 High power (needing >450 mAmps) Wifi Adapters, far away from PC, Bought Active Repeater USB Extension Cable with 4 Ports & power port at far end http://www.ebay.com/itm/33FT-USB-2-0-Male-to-Female-Extension-Cable-Hub-Splitter-Adapter-with-4-USB-Port-/390846115254 (see 2nd picture for single pin adapter port on it) & Powered it by plugging it with locally bought (medium quality) 2 Amp 240V AC to 5V DC Power Adapter

    Even 4 Wifi Adapters run fine (appear to) using this setup, but running chassis fan, dimly lighted Power & HDD LED, even when PC is switched off is bit scary & surely mean 5V & some current is flowing all though that 10 meter extension cable into my USB port & powering stuff.

    Can this cause damage? and what should be my concerns. Of course I can't switch off the power adapter (lying 10 meters away from PC) every time I switch off my PC to prevent this.

    ** PICTURE OF SETUP**

    http://imgur.com/mcmsBPy

    • Answers
  • OmnipotentEntity

    Yes, in theory. My hunch is yes also in practice.

    I've personally experienced both motherboard damage from back power from a misbehaving USB device.

    Power where power is not expected can definitely cause issues.

    It should be noted that I don't entirely understand how you have everything hooked up. But if power is going into the computer backwards I would consider that cause for concern.


    • Related Question

    power - Can I charge USB devices from a powered hub that isn't connected to a PC?
  • Anodyne

    This will probably sound familiar to most of you... In my home, we have a whole bunch of devices that can be charged via USB (two iPhones, a BlackBerry, an iPod Touch, etc ad nauseam). We also have a bunch of USB chargers, each of which has a single USB port on it. I'd like to have something permanently connected to AC power with at least 4 USB ports on it, so we can just plug devices in and don't need to go looking for a free outlet.

    So here's the question: if I buy a powered USB hub, will that do the job even if I don't connect it to a PC? Ideally if you have a hub that you can personally verify will be suitable, let me know the manufacturer and model :-)

    Thanks in advance!

    EDIT: The solution I eventually went for was this:

    Kensington 4-Port USB Charger for Mobile Devices (Europe)

    There's also a US version here:

    Kensington 4-Port USB Charger for Mobile Devices (USA)

    It arrived yesterday, so I used it to charge the following devices, all at the same time, overnight last night:

    I can't say anything about the charging speed (as I left it overnight) but all devices were fully charged this morning.


    • Related Answers
  • 8088

    Check: Transform a USB hub into the ultimate DIY gadget charger

    I'm talking about a standard USB hub--those little accessories that multiply one of your PC's USB ports by a factor of four, five, six, or even seven. I took a spare seven-porter--the Belkin F5U701 ($20)--plugged its included AC adapter into a nearby wall outlet, and started loading it up with devices. A few minutes later, I was charging six devices via USB with no apparent problems--and I still had a free port available for yet another device.

    alt text

  • Kez

    Although the voltage is consistent across all USB chargers (5V), I believe the ampage does vary. I have heard reports that iPhones charge really slowly or not at all using a Blackberry charger. Same with Blackberry chargers, they are not all the same ampage for each model.

    I would just buy a 4/6-way power surge-protected strip or something and plug all of your existing chargers into that.

  • jfmessier

    You might want to keep in mind that some hubs may share or divide the amps across the ports, and you may get lower performances, even if only one device is actually connected. You may want to test the actual voltage/amperage with a meter on the ports of the hub.

  • 8088

    TruePower UCS Power Outlet with USB ports from FastMac:

    outlet

    Our custom TruePower power outlet solution includes two Universal Serial Bus (USB) charge ports in addition to the two standard three prong power outlet ports.

    Perfect for charging any USB powered device including- mobile, iPod, iPhone, PDA, MP3, PSP, MP4 player & digital camera.

    Installation: This item can be installed on any existing wall outlet.

    We will have an installation video available shortly so that you can see exactly what is involved and if this is something you feel comfortable doing on your own or if you will need assistance.

    Please also note that the USB ports only draw power when something is physically connected to the port. We didn't want a vampire port that continually sucks and wastes power when not in use so this was one of the features on the top of our priority list during the design phase.

    Although it says "any USB-powered device including ... iPhone", I'm waiting for my pre-order to ship before finding out whether the iPhone 3G and 3GS will be able to charge through this outlet. The 3G and 3GS have special requirements involving an authentication chip from Apple, which are only in Apple-approved products. I guess I'll just have to wait and see!

  • shf301

    I have never tried with a powered USB hub, but there are USB wall chargers that do exactly what you want. See this result search result of USB wall charges at Amazon.com.

    Some of those devices specifically mention iPod support. I think I tried one with an iPod Nano and it worked fine. I have used one with a Sansa mp3 player and a Creative Zen.

  • Anodyne

    The solution I eventually went for was this:

    Kensington 4-Port USB Charger for Mobile Devices (Europe)

    There's also a US version here:

    Kensington 4-Port USB Charger for Mobile Devices (USA)

    It's basically a mains plug with 4 USB ports. It hasn't arrived yet, but I'll update here when I've tried it, along with information about the devices it works (and doesn't work) with.

  • nik

    ThinkGeek: AC to USB Power Adapter -- for a portable solution.

    alt text

    • Charge and power your USB devices without a computer
    • Intelligent IC chip inside recognizes a fully charged battery and automatically switches to a saver mode to prevent overcharging and short circuit
    • While plugged into an AC outlet, your device powers and charges simultaneously
    • Works with any kind of USB device that needs power
    • Small and compact size; easy to carry anywhere
    • LED indicates charging status: Red for Charging, Green for Charging Complete

    Update: You'll get a decent 1-Amp (or more?) adapter from your nearest Apple store.

    • Keeping a 1-Amp charger handy is useful for many gadgets that can charge faster with more available current; also, with multiple devices being charged together, you are better of with a higher rating (current does get shared across them, giving each a lower charging rate in the end)
    • Apple stores are usually quite accessible (but depending on your country, this might be a costlier deal)
      • Whatever you do, get a good quality adapter or you might burn off your gadgets!