In today’s world of mass portable devices with USB connectivity, charging should be as simple as plug and play. Unfortunately, it’s not that easy. Take me for example. On my desk I’ve got a Google Nexus 5, Dell Venue 8 Pro, Apple iPhone 4, and several generations of iPad. Each one came with a completely different power adapter for charging! My Nexus will charge off of almost anything, my Dell Venue 8 Pro is quite picky, but Apple might be the most confusing of them all.
The reason is USB charging has not been well standardized until recently. Apple has been charging devices via USB with special signaling since the first USB connected iPod. Devices determine whether and how fast to charge, and make that decision based on different non-standard methods to recognize “their charger.”
Take for example the following charging signals commonly seen today:
Apple 2.4A (12W) (iPad Air / iPad Mini, likely any subsequent iPad releases)
Apple 2.1A (10.5W) (original iPad through iPad Retina)
Apple 1A (5W) (first seen with the iPod all the way back in 2002, commonly found with all iPhones including the newly released iPhone 6/6 Plus)
Dedicated Charging Port, DCP (wattage varies per device) (often referred to as the Android charging signal, common for almost all non-Apple devices)
Samsung 2.4A (12W) (usually seen with Samsung tablets, potentially some phones)
USB-IF BC1.2 CDP 1.5A (7.5W) (the official USB charging standard, it’s not well adopted yet, but more devices are becoming compliant)
What exactly does all of this mean?
In short, taking my Dell Venue 8 Pro as an example, I can’t plug it into just any USB charger and expect it to charge, it works on Android and Apple 1A signals but won’t charge on any of the others. Or if we take my iPad Retina and plug it into my iPhone 4 charger, it’s going to charge at an overly slow rate.
Because of scenarios like these, most users have a preconceived notion that they must use the stock charger that came with their device. Sometimes with the fear that if they do not, their device won’t charge, or worse, could actually be harmed.
Fortunately this isn’t the case. In fact, most devices on the market can actually charge from the Apple 1A signal as it has unofficially been adopted as the universal USB charging standard; mainly because it’s been around for so long. Also a device will only pull as much power as it needs, so using a more powerful charger may actually help your device charge faster. The newly released iPhone 6 and 6 Plus ship with the standard Apple 1A charger, but will charge much faster on the Apple 2.1/2.4A chargers or another charger that the iPhone 6 recognizes.
Many consumers don’t realize they can downsize their growing pile of stock chargers for a more convenient multi-port charger that can charge almost every USB charging device in their home simultaneously from just one AC wall outlet. Take our flagship multi-port charger, the Plugable USB-C5T (temporarily out of stock 10/3/2014). It has 5 USB charging ports with enough power (7.2A, 36W) to charge two iPads and three iPhones concurrently (or three iPads and one iPhone, etc) at their maximum charging rates.
The Plugable USB-C5T, bringing order to chaos.
Three of the C5T’s USB ports simulate the standard Apple 1A signal which will charge most devices, including my picky Dell Venue 8 Pro, but where the C5T really shines is with the two outer ports which are equipped with a smart charging chipset made by the folks at Genesys Logic. The GL888F chipset can simulate almost all of the aforementioned charging signals (sans Apple 2.4A) and will intelligently select the best one for your device. This is great because if your device happens to not be compatible with the standard Apple 1A signal, chances are it will charge off of the smart ports.
Great. Sign me up!
Not quite yet, but we’re almost done. Have you ever tried to charge your device from your computer only to be let down by slow charging or no charging at all? If so, you’re not alone, it happens to the best of us. When you connect a phone or tablet to a computer, the device wants to put itself into a mode where data can be synced. Often syncing while charging either isn’t possible or is extremely slow, only drawing around 0.5A from the host computer’s USB port. This behavior is also expected on all USB hubs unless they are BC1.2 compliant. The BC1.2 charging signal, CDP (charging downstream port), is compatible with all current Apple Lightning Cable devices like the iPad Retina / iPhone 5 (and newer) and many new Android and Windows Mobile devices are moving this direction as well.
Our flagship 7-port USB 2.0 hub, the Plugable USB2-HUB7BC, is BC1.2 compliant and devices can charge at up to 1.5A while syncing data. The HUB7BC can also act as stand alone dedicated charger when the computer is turned off or not connected. To many this is the proverbial “holy grail” of USB charging despite slightly slower charging rates (1.5A) compared to a dedicated smart charger like our GL888F (up to 2.4A) equipped USB-C5T due to the added convenience of charge and sync.
In a time where USB charge and sync functionality can be unnecessarily complicated, we work hard to deliver simplicity to the equation. With charge and sync being available on nearly any BC 1.2 compatible device, which is most mobile devices produced in the last few years, why would you want to haul around an individual charger for each device?
Plugable does extensive testing to determine which devices charge at what rates on our chargers and charging capable hubs. This turns out to be important, because USB charging is not (yet) well standardized, and results vary by device.
If you’re looking for a charger, our data on charging rates will tell you exactly how much current, in milli-amps, specific devices will pull from our chargers. The higher the number, the faster the device will charge. We’ve tested many popular Apple and Android devices, and add new results frequently.
With the release of Apple’s iPhone 5 and iPad Mini and their new “Lightning” connector, we wondered if Apple would update the charging behavior of their devices. If you don’t recall or aren’t aware of the convoluted story behind charging Apple’s products (the 30-pin generation), here is a refresher from a post we published a while back.
As far as we’re aware Apple hasn’t announced any changes in regards to their USB charging spec compliance with these devices, so we weren’t exactly optimistic. But we grabbed our 4 Port Hub which complies with the Battery Charging 1.1 standard, connected an iPhone5 and iPad Mini to it (without connecting the hub to a host computer), and measured the charge rate. In true X-mas miracle fashion, both devices charged at the full rate equivalent to what you would get by using Apple’s wall charger; instead of the old behavior where 30-pin generation devices would charge at 500mA max (with a computer attached) and not at all without (unless the iOS device itself was powered off).
There’s even icing on the cake; in our test iPhone 5 and iPad Mini charged at a HIGHER rate via the hub than with Apple’s wall charger, we calculated 1.1A through the hub whereas the in-box charger provides only 1.0A. Which equates to reaching a full charge from 10% battery in about 1.5 hours on iPhone 5, compared to 1 hour 50 mins with the wall charger.
What’s more (yes, there’s even more!) both the iPad Mini and iPhone 5 charged at the accelerated rate via our hub while syncing them to a computer. So they appear to be making full use of the great possibilities with the USB Battery Charging 1.1 standard. It’s wonderful news, and a great move by Apple.
Here’s a breakdown of all the charge rate data we recorded:
In Box Charger
Synced to PC
Please feel free to comment here with your experiences, or e-mail firstname.lastname@example.org for any questions or inquiries — we’re always glad to help!
Microsoft’s official statement is “Windows RT uses class drivers and in-box drivers exclusively, departing from a common driver added scenario on the x64 or x86 architectures.” (see Microsoft policies). There is no DDK. Officially, installing drivers on Windows RT is not supported.
That said, it turns out there is at least oneWindows ARM driver that exists (probably built and extracted from a full Windows RT platform development kit), and as a user you can install those drivers on a normal, unmodified Microsoft Surface device at least.
Whether Microsoft will close this mechanism in the future is unclear.
Below is a more complete list of all the Plugable devices which can and can’t be made to work with the surface today. Most use the drivers already built into the RT, so none of the above is a concern — but Windows RT is “special” so check for compatibility before assuming a device will work!
What devices work out of the box with ARM-based Windows RT (without a 3rd party driver install)?
Plugable Windows Easy Transfer Cable (Although Windows Easy Transfer is available on Windows RT devices, the driver for USB Easy Transfer cables is not. Kind of surprising since on Windows XP – 8, this is a driver developed and provided by Microsoft in the box)
What needs a driver package and has one available for ARM-based Windows RT devices
We recently received a Raspberry Pi at the Plugable offices and we have been using it to test how our various devices interact with it. The Raspberry Pi has 2 USB 2.0 Ports, and no USB 3.0 ports, so our testing was focused on USB 2.0 devices and a couple USB 3.0 storage devices.
All of these tests were carried out on a Raspberry Pi Model B using the latest version of Raspbian wheezy. Here’s a video of the full setup, followed by a bunch of detail about our tests:
Plugable USB 2.0 10 Port Hub with 2.5A Power Adapter – Causes the Raspberry Pi to reboot upon connection, because it supplements the 2.5A wall power with 500mA from the upstream port. This is too much for the Pi., but just at the moment it is plugged in. If you plug the 10 port hub in when the Pi is powered down, you can boot into the Pi and all will be well. But since there are better options (like the 7 port hub above), we don’t recommend our 10 port hub with the Pi.
USB2-2PORT – Causes the Raspberry Pi to reboot upon connection. This is simply because this is an unpowered hub. Only hubs with their own power adapter should be used with the Pi.
USB3-HUB7-81x – USB HID devices(Mice, Keyboards) are known not to work with this hub on the Raspberry Pi.
USB3-HUB81x4 - USB HID devices(Mice, Keyboards) are known not to work with this hub on the Raspberry Pi.
USB2-SWITCH2 – No issues
The common pattern with all devices is you must have one of the powered usb hubs above and connect the device through that. If you don’t, the Pi won’t be able to handle the power draw, and it will drop voltage and reset.
Listed below are our latest updates about how to make your Plugable products work on Mac OS X 10.8 Mountain Lion with all the caveats shared by customers. If you read this post before and notice changes, it’s because we’ve revised our advice based on differences between our test results and what many customers were reporting. For now, in all cases we are recommending the solutions that have worked for everyone.
Any Plugable products not listed below have not yet been tested or have no Mac support (USB 3.0 graphics adapters, USB 3.0 docking station, Windows Easy Transfer cable).
After installation and reboot, plug in the adapter.
Go to network settings. If a new USB Gigabit interface hasn’t been created, then click the plus button, and add a new interface for the USB Gigabit Ethernet adapter.
Click the gear button, choose to set the service order, and drag the Gigabit Ethernet interface to the top of the list to make it your primary network connection. Approve the change to return to the main network settings screen.
Click Apply in network settings.
If the status in network settings goes green with a good IP address (not 169.x.x.x), the adapter is working properly.
Uninstall any old DisplayLink drivers before upgrading from 10.7.x.After upgrade, download and install the production version of DisplayLink’s v1.8 driver (or later) for OS X at DisplayLink’s Mac driver page.
Note that the performance of USB graphics on Mac is not yet at the same level as Windows. And some customers have reported crashes and hangs after installing DisplayLink drivers on Mountain Lion. See DisplayLink’s Mac user forum for the latest details. There is a specific thread on possible causes of Kernel panics.
We are filing bugs with DisplayLink based on Plugable customer feedback. If your system is not performing properly once you have installed the latest DisplayLink drivers, please contact us at email@example.com for assistance.
10.8 has a regression where USB Hard Drives attached to a Mac through a USB hub may report “drive wasn’t ejected properly” on return from sleep. We have customer reports of this issue in particular with USB 3.0 hubs like USB3-HUB4
Please feel free to comment here or e-mail us at firstname.lastname@example.org with your findings, questions, or problems. We’re here to help.
In short, you can plug the four-port charger into an electrical outlet, attach a Samsung Galaxy S III’s to the charger via its USB cables, and the Galaxy S III phone will recharge at nearly the same rate as if it was plugged directly into an electrical socket.
This works because the Samsung Galaxy S III supports the USB battery charging specification (aka BC 1.1/1.2). Following the battery charging spec means that customers can get a predictable result for recharging when the Galaxy S III is plugged it into a USB hub that also supports the charging spec. The Plugable four-port hub and fast charger is such a hub. Plugable’s 10-port and seven-port hubs don’t support battery charging even though they do have their own power adapters.
Anyone who’s ever tried to recharge a phone or tablet computer just by plugging it into a standard USB 2.0 hub knows that results aren’t often positive. Yes, sometimes it seems to work, but it’s almost by accident. In general we can’t guarantee the desired results when either the device or the hub don’t comply with BC 1.1/1.2.
With the Samsung Galaxy S III, we can say unequivocally from our own testing that it will recharge when plugged into Plugable four-port hub and fast charger. We hope the Galaxy S III is in the forefront of a wave of devices that support the battery charging spec. But for now, the Galaxy S III’s support of the spec is another plus for a phone that’s already winning rave reviews.
Plugable USB 2.0 4-Port High Speed Hub with 12.5W Power Adapter and BC 1.2 Charging Support for Andr...
“The only reason I bought this was that my computer’s USB doesn’t provide enough power to charge my iPad 2. Unfortunately, this hub doesn’t charge the iPad either, so it’s completely useless to me.”
“Bought this as a powered USB hub so that an iPhone and iPad could be connected to a MacBook Pro and charge both. Does not work.”
“So much for a ‘powered’ usb hub, it doesn’t power my iPad …, which defeats the purpose of me even getting it.”
It seems like it should be so easy. You have a hub that is plugged into an electrical socket. Your iPad is plugged into the hub. It should recharge. But it says, “Not Charging.” Why?
It all has to do with how electrical current is supposed to flow through USB ports and with confusion caused by proprietary behaviors that Apple has implemented in its product ecosystem that lead to different recharging results in seemingly identical scenarios.
If you want to avoid the answer to the “why” question and just know how to charge your Apple iPad, iPhone, or iPod Touch when it’s connected to a self-powered hub, here are your two options.
Option 1: The iPad/iPhone/iPod is connected to a hub that is plugged into an electrical outlet and a computer simultaneously. The Apple device will recharge by pulling current at a rate of 500 milliamps when attached to this hub (the hub’s power supply must have enough amperage to provide this current).
The iPhone and iPod both will indicate they are charging in this state. Total recharge time will be about half as fast as when they are plugged directly into a Mac’s USB port or an electrical outlet.
The iPad will display “Not Charging” in this state if its screen is enabled. Put the screen to sleep with the Sleep/Wake button on the iPad’s exterior, and the device will start to charge. In our tests, an iPad charging at a 500-milliamp rate will add about 10% to its battery meter every 1.5 hours.
Option 2: The iPad/iPhone/iPod is connected to a hub that is plugged into an electrical outlet but not a computer. The Apple device’s power must be completely turned off for the device to recharge when attached to this hub. Here are step-by-step instructions.
Plug the iPad, iPhone, or iPod into the hub. If the device was previously shut down, it will turn on upon sensing power from the hub.
Perform Apple’s shutdown routine for the device. You can’t just let the screen go blank. You need to hold down the physical Sleep/Wake button on the exterior of the iPad, iPhone, or iPod until you see the red arrow on screen that you can swipe to turn off the device.
Swipe the red arrow to complete the shutdown process.
Once turned off, the Apple devices will draw power through the hub at the 500-milliamp rate.
Please be aware that if you attach multiple Apple devices at one time to your hub in either scenario that you might start to exceed the amperage available in your hub’s power supply. We cannot verify charging will occur once this has occurred.
In our tests, when we overloaded the available power supply, we saw varying results in how the attached devices consumed power. However, we did observe that iPhones and iPods (not iPads) still would charge–albeit very slowly–when drawing power at the 100 milliamp rate.
If you want to know more about how USB power works and where Apple deviates from the USB 2.0 standards, read on.
USB Power Primer
The USB 2.0 spec permits devices to pull current at a default rate of 100 milliamps from a USB 2.0 port (we’ll call this the host)–enough to power a mouse but hardly enough to charge an iPad battery.
If a USB 2.0 device needs current at faster rate than 100 milliamps to function, it is allowed to negotiate with the host to increase its consumption rate to a maximum of 500 milliamps from the host’s port.
When a device tries to draw more current than is available to the host–often described as overcurrent–you can end up with a warning that there isn’t sufficient power to meet the device’s needs. This warning might appear on the host (e.g., a popup in the Windows taskbar, like the one shown to the right). But others, like the Mac, disable the port without any warning, often creating the erroneous impression that the devices are broken. They aren’t–they’re just not able to draw any power from the port anymore. A reboot re-enables the port, but the port will shut down again if you don’t take any action to reduce the power consumption by the mix of devices attached to the port.
When multiple devices are connected to a single USB 2.0 port via an unpowered hub, it can lead to an overcurrent situation, especially because all the devices attached to the hub have to share the 500 milliamp current available through the host’s port. The hub can only split the available current, not multiply it.
A self-powered USB 2.0 hub–that is, one with its own AC adapter–can alleviate this situation, because it can tell the host, “Don’t worry, I can take over as the provider of the current that these devices want.”
For example, if the hub’s the power supply can deliver current at a rate of 2.5 amps (100 milliamps = .1 amps), and there are five ports on the hub, the host now can let each USB 2.0 device attached to a port on the hub negotiate for up to the USB 2.0 maximum of 500 milliamps (2.5 amps / 5 ports = 500 milliamps / port) without exceeding the hub’s power capacity.
When There’s No Host
When a self-powered hub is plugged into an electrical outlet but not connected to a host–think of it as a USB-based power strip in this configuration–it becomes wildly unpredictable how devices attached to the hub will behave when trying to draw power. The original USB 2.0 spec just didn’t envision how important USB-based power consumpution would become.
Without guidance from the spec on what to do in this scenario, device manufacturers can implement whatever behaviors they desire. Some devices will pull power at the same rate as they do when attached to a host-connected hub. Other devices will downgrade to the 100 milliamp default. Certain devices may try to exceed the 500 milliamp limit in the USB 2.0 spec–not necessarily a bad thing for improving device charging times.
In the case of the Apple iPad, iPhone, and iPod Touch, we saw different power consumption behaviors depending on whether the devices were powered on or off. When powered on, they could draw only 100 milliamps of power. When turned off, as explained earlier, they would draw 500 milliamps of power.
This image shows an iPad's power consumption when plugged into a self-powered hub that has no data connection: On the left, the iPad in a powered-on state is drawing 100 milliamps from the hub. On the right, the iPad in a powered-off state is drawing nearly 500 milliamps from the hub. Click the image for a larger view.
If you have questions about whether your specific phone, tablet, or handheld device will charge if it’s plugged into a hub that’s being used like a power strip, the only way to know is to plug the device into the hub and see what happens.
Apple Bites Back
Apple makes great devices, but it also makes the USB-charging situation even more confusing. As explained, the iPad, iPod, and iPhone will recharge when pulling 500 milliamps of current. But Apple has engineered these devices to prefer to pull more than USB 2.0-specified maximum of 500 milliamps. However, to do so, the devices must be connected directly to USB ports that have been customized with Apple’s proprietary charging extensions.
Click the image to go to Apple's support document that explains the proprietary USB charging behaviors in Apple's product ecosystem.
In a support document on Apple.com about USB charging, Apple explains that “some Apple computers and displays can provide up to 1100 milliamps [1.1 amps] … through the port to which the Apple peripheral or device is connected.” In other words, when an iPad or iPhone is connected to a newer Mac as its USB host, an iPad can draw current at more than twice the standard USB 2.0 rate.
The current isn’t delivered at as fast a rate as the 2.1 amps provided by Apple’s special AC wall adapter for recharging an iPad. Gizmodo has done a speed test of the fastest (and slowest) ways to charge an iPad. Charging via a Mac’s USB port at the 1.1 amp rate was the slowest way in the Gizmodo test, but it still got the job done. As we’ve identified, even 500 milliamps will get the job done as long as the iPad’s screen or power is off.
And 500 milliamps is the only rate that you’ll ever get from a Windows PC or any other USB 2.0 host that lacks Apple’s proprietary charging extensions.
You might be thinking that the ideal solution is just to get a Mac plus a USB hub. Then you can have all the benefits of multiple USB ports and can use one to charge your iPad, iPhone, or iPod Touch at the faster rate available when connected directly to a Mac.
Unfortunately Apple only allows these devices to draw the 1.1-amp current from a Mac’s USB port via a direct connection. Apple explains: “An Apple peripheral device must be plugged directly into an Apple computer or display. Apple peripheral devices connected to hubs will not have access to extra power above the standard USB specification of 500 milliamps.”
In other words, if you connect a hub–powered or not– to your Mac, you lose access to the proprietary charging extensions in the Mac’s USB port that allow the Mac to charge your iPad, iPhone, or iPod at the 1.1-amp rate.
If you want to know how Apple establishes these proprietary USB charging behaviors, Ladyada.net has a great video and blog post on the technical underpinnings of the mysteries of Apple device charging. As she explains, it has to do with how Apple has engineered its devices to deviate from the USB 2.0 spec when they sense a special amount of voltage from the power source on two of the four lines that make up a USB connection.
Where Do We Go from Here
There is hope that in the future USB-connectable devices will consume power in a way that meets the “universal” promise in the USB name.
There is now a USB battery-charging spec that was developed to standardize USB-based charging behaviors. Unfortunately, the spec has not yet been widely adopted. And the lack of any strong industry efforts to market or brand spec compliance makes it difficult for customers to identify and buy products that already follow the spec.
In a world where following this spec was the norm, you could plug your hub into a wall, attach a bunch of devices, and get them all to recharge in a reasonable and predictable amount of time without having to take any special action.
Regardless of what happens in the future, our aim always is to make sure that you know what to expect from Plugable products today and that you are satisfied with the ones you purchase. If you have questions or comments about this article or device charging in general, feel free to leave a reply here, and we’ll respond.
If you have other questions about any Plugable hubs, docking stations, adapters, or cables, get in touch with us through our support website at support.plugable.com or e-mail us at email@example.com. We’re here to help.
As both support the new standard, you can fast charge — even without a computer attached.
A few notes:
* The Kindle Fire has a standard USB micro-B connector, but the Fire doesn’t come with a USB cable in the box. You’ll need to buy that separately (in the video, we show using a cable borrowed from a Kindle Touch).
* The Kindle Fire will actually charge at up to 850mA. The video shows it pulling 650mA, because the Kindle is almost fully charged.
* The Apple iPad/iPod/iPhone are *not* BC 1.1 compliant, so this support is of no use for charging those devices at a faster rate. And the iPad won’t charge while the screen is on when connected to any standard USB 2.0 hub.
If you’re curious about our measurement rig, it’s a nice simple setup – just a multimeter and some passive components. Give a comment if it would be helpful for us to post the components we used.
We welcome any comments. Thanks!
Plugable USB 2.0 4-Port High Speed Hub with 12.5W Power Adapter and BC 1.2 Charging Support for Andr...