It’s frustrating, but many devices won’t charge on a powered USB port the way you’d expect. This includes most Apple, Samsung, and Google phones and tablets.
This is because the phone must choose how much power to pull, and by the original USB spec devices are supposed to only draw 100mA at first. They can then negotiate up to 500mA. This negotiation requires a PC that’s attached and on.
The iPhone and most other non-tablets will charge at 500mA on a standard USB port this way. But they can also charge faster (up to 1000mA) if a port sends a special, non-standard signal to say “I’m an Apple 1A charger”. It does this by shorting the data lines (disabling data transfer at that point) and putting a specific signal voltage on each of USB’s two data lines. Even though it’s not a standard, nearly all phones and tablets on the market today recognize this signal.
For tablets like the iPad, this mechanism is even more important. Because these batteries are larger, charging at 500mA would be slow. The 1A “I’m an Apple charger” signal becomes the minimum for the tablet to report charging at all.
This new Plugable USB-MC1 Charging Adapter simulates that 1A signal, turning any powered USB port with at least 1A power available into a charging port.
This also has the effect of disabling data transfer, so you can safely plug your phone or tablet into a public computer and the phone or tablet will charge, but not be visible to the computer otherwise — you’re safe to charge without worrying about exposing your data.
Leave this attached to your phone or tablet’s USB charging cable to greatly expand the set of USB ports you can charge on.
Above on the left is an Apple iPad connected to a standard USB hub that has plenty of power available, but you can see on the iPad’s screen in the upper right, that it’s not charging.
On the right is the same setup with our adapter in-between the iPad and the hub. You can see the iPad now sees the hub as a charger, and is charging the battery.
How many of these adapters can be safely used on a powered hub at once?
The AC adapter of your powered hub needs to be rated for at least 1A per USB charging adapter connected. If it is not, over-current may be triggered (causing all power to the hub to shut off), or the hub circuit or power supply may heat up from too much current being pulled through by the device. If this happens, remove devices until you’re back within the rated amperage.
So before you go running off and buy 10 of these little dongles to turn your 10 port hub into a charging super station, keep in mind that you are still limited by how much power the USB hub has access to. For instance, our 10 Port USB 2.0 Hub comes with a power supply of 2.5A, that is only enough to actively charge 2 devices at the Apple 1A Charger rate with .5A left for spare devices on the hub.
The Plugable USB-MC1 product page has more detail, including a table of charging rates with some common phones and tablets. Have any other questions? We’re happy to help. Feel free to comment below or email firstname.lastname@example.org anytime. Thanks for your support of Plugable products!
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