Quick Charge and USB-C: Navigating the Next Generation of USB Charging

It’s been over 15 years since the modest USB port first became a fixture on computers around the world, initially as a way to connect basic peripherals and then as a standard for faster data transfer. But the connectors and speeds people have gotten used to—USB-A, Mini-USB, Micro-USB, USB 2.0—have gotten a bit long in the tooth, as the original port and cable designs weren’t built to handle the power-hungry, fast-data devices everyone has come to rely on. Fortunately, a new generation of connectors (USB-C) and a fresh mélange of fast-charging standards (including USB Power Delivery and Quick Charge) have arrived to charge those devices’ larger batteries much faster than before.

The promise of faster charging may be enticing, but we don’t think most people should toss out—ahem, we mean recycle—their current devices and accessories quite yet. The availability of new, faster-charging devices is limited right now, and because the implementation and compatibility among manufacturers is still a mess, you won’t always get the promised benefits. But if you already have a phone or tablet that can take advantage of USB-C, USB Power Delivery, or Quick Charge, you should make sure to buy the right accessories to get the most out of that gear.

First we need to talk about the connectors and ports you can find on devices. The rectangular port that’s been on all but a few computers this century is technically called a USB-A port—it’s supposed to appear only on source devices such as computers and chargers. Plug in a USB cable, and the other end of the cable connects to a target device using one of a handful of connectors, generally either USB-B (common on big, stationary devices such as printers), Mini-USB (a smaller size common on older cameras and hard drives), or Micro-USB (even smaller, and found on everything from phones to tablets to battery packs).

Depending on the devices at each end of the cable, each connector is capable of some combination of one of multiple standard power levels and one of multiple data standards. Fun, right? If two devices don’t quite mesh—for example, if you connect a fast-charging-capable phone to a slow charging port, or copy data from a speedy hard drive to a slow computer—the slower side always prevails. The important idea here, however, is that a specific connector doesn’t determine the connection’s power or data capabilities.

Though USB power has gone from less than 1 amp of current (1 A) in its earliest incarnations to more than 2 A today, devices have maxed out the data and power capabilities of these connectors. We’ve talked before about how you can think of voltage in an electrical system as being similar to water pressure, and how you can think of the current or amperage as the size of the pipe. Traditional USB has always offered 5 volts, which is just a trickle—that’s a lower amount of voltage than what you get from a car battery (12 V) and much lower than residential voltage (110 V AC in the US). Because volts × amps = watts, if your iPhone is charging at 2 A over USB, it’s using just 5 V × 2 A = 10 W of power, in contrast to something like a 32-inch LCD TV, which might use close to 100 W. The higher the numbers, the faster your device will charge.

Quick Charge

Enter Quick Charge (QC) from Qualcomm. Devices with QC technology inside are capable of safely pushing and pulling higher voltages than the USB standard technically allows, while still using the same USB cables you’ve probably owned for years. That’s possible because when you plug a QC-capable device into a QC-capable source, the two communicate differently to manage the extra power. Since the first version of QC debuted in 2013, QC has evolved to support ever-higher voltages that can charge compatible devices ever faster—20 V in QC 3.0, the latest iteration, or four times the voltage of standard USB. As an example of what this means in real-world use, the HTC 10 and LG G5 smartphones, which both feature QC 3.0 support, promise to charge the first 80 percent of the battery in about 35 minutes.

Specifically, Quick Charge 3.0 devices can start charging at 20 V when completely empty, with the power slowly stepping down as the battery fills up. The process is a little like filling a big water balloon with a fire hose: You can fill the balloon most of the way very quickly, but you need to taper off the water pressure at the end so that you don’t accidentally burst the balloon. In this case, a burst balloon is analogous to what engineers call thermal runaway—a fancy term for "exploding battery." It’s also why we don’t recommend buying cut-rate QC accessories. Though genuine QC accessories have to be certified safe and compatible, low-quality components in counterfeit goods may not be—a real risk considering that heat buildup is the main factor in horror stories about exploding batteries and melting gadgets.

Bottom line: If you have a QC-enabled device (right now, the category consists mostly of high-end Android phones) and a high-quality charger, the extra speed can be especially convenient for reviving your dead phone before you run out the door.

But even though speedy charging is a handy feature, it isn't something that should sway you from another phone that you like as much as or more than a QC-capable model. For one thing, devices have to get certification from Qualcomm (through UL) to support QC, which can increase the manufacturing and development cost and, thus, the retail price. But the biggest cost in choosing a QC-capable device isn’t the cost of the phone itself but of all those accessories you may have picked up over the years: Any standard chargers around your home and in your car will charge a QC phone at the same (slower) speeds as they do a non-QC phone—both the device and charger need to be QC-capable for you to see any benefit. So to get the promised faster charging, you’ll need to buy new chargers. Beyond that, the voltage tricks that QC devices play are most helpful when the battery is almost dead. If you’re merely hoping to top off a battery that’s already above 60 percent or so, you’ll see far less benefit.

USB-C

Manufacturers can technically implement Quick Charge in any USB port, but that seems less likely to become more common going forward due to the new USB power standards available with USB-C connectors.¹ While QC works with the cables you already have, USB-C is a completely new connector that will soon replace ports on all sorts of devices. First popularized by Apple’s 12-inch MacBook and the Google Nexus 6P smartphone, the USB-C connector can be present on a source device or a target device (or both), and it can use either the older USB standards or the newer, faster power and data-transfer protocols. (It’s also a reversible connector, so you won’t end up trying to plug in your USB cables upside down. Every. Single. Time.) We’ll ignore the data-transfer part for now, since the power portion is complicated enough.

Since USB-C is a type of connector, and we’ve established that connectors don’t determine the underlying capabilities, it’s important to know that USB-C connectors can provide you with the performance of almost any generation of USB that has come before—what’s important is what’s behind the connector or at the other end of the cable. For example, if you were to have the right cable to connect the latest and greatest smartphone with USB-C into an old, low-power, USB-A port, the phone would likely alert you to the low power and refuse to charge. The slower protocol always wins out.

On the other hand, USB-C connectors can take advantage of the newest power standard, USB Power Delivery (USB PD), which has a maximum power output of 100 W (20 V / 5 A), meaning manufacturers can use it to power everything from laptops to TVs. Most devices, though, will likely fall somewhere between traditional USB power and USB PD. Going back to our water analogy, many small and inexpensive USB-C devices—think budget phones and their accessories—will still max out at USB’s old 5 V "pressure" but with a slightly larger 3 A “pipe.” Larger and flagship devices, such as the biggest tablets and top-of-the-line phones, will likely take advantage of what is essentially Power Delivery “lite,” pushing up to 20 V and 3 A through either USB-C cables or USB-C–to–Micro-USB cables. And manufacturers could start to use the full 100 W (20 V / 5 A) Power Delivery standard on anything from monitors to large laptops to network-attached storage devices, so long as both ends of the connection use USB-C.

But just as Quick Charge has multiple generations available, and requires compatible devices on both ends to see a benefit, these variations in USB-C are sure to drive people mad for the foreseeable future: Two different USB-C devices won’t necessarily be able to run on the same type of charger. And just as using counterfeit QC accessories can be risky, stores are being flooded with cheap, noncompliant USB-C accessories, some of which have the potential to damage laptops and phones; in fact, it’s become enough of a problem to warrant a crackdown by some retailers. With great power comes great responsibility, and these new standards are bringing a lot more power to everyone’s devices.

Quick Charge and the new USB-C and Power Delivery standards are gaining just enough traction for us to research and test compatible chargers and batteries, so you’ll start to see us make Quick Charge and USB-C picks in related guides to help anyone who wants the faster speeds. But if you don’t have a fast-charging device, and you aren’t sure whether you’ll be getting one soon, you have no need to spend the extra money on a Quick Charge or USB-C charger right now—you won’t see any benefit.

In our photo of the most common connections, we mistakenly used a USB 3.0 Type-B cable, instead of a USB 2.0 Type-B cable as planned. We’ve updated the caption to refer to the 3.0 connector, and we apologize for any confusion.

Update 8/25/16: After we published this article, Qualcomm reached out to us to clarify that although the QC 3.0 standard supports 20 V, "none of the QC accessories currently give 20V, and mobile devices only use a max of 9V.” Additionally, the certification process we mentioned applies only to QC-capable accessories, not to target devices.