How Does Fast Charging Work? Every Standard Compared

In the increasingly competitive smartphone market, people meticulously examine each and every feature that smartphones have to offer, from screen size to processing power, before choosing the best smartphone for them.

A relative newcomer to the ranks of sought-after features is fast charging. Technology now allows for a quick charge during the limited downtime we find in our busy day-to-day lives. Who wouldn’t want a smartphone that charges in minutes instead of hours?

If only it were that simple. Charging standards are a complicated mix of chemistry and physics, and each has its own sets of limitations, with incompatibility an issue as well. To make matters worse, smartphone manufacturers tend to slap confusing labels on their charging tech.

So how does fast charging work? Take a deep breath. Our guide to the most popular wireless charging standards on the market breaks them down to their most basic level. Here is everything you need to know about Samsung Adaptive Fast Charging, USB Power Delivery, Qualcomm Quick Charge, OnePlus Warp Charge, and more.

The basics

How fast charging works

Before we dive into the weeds, let’s start with the fundamentals.

Every smartphone has a battery, and every battery delivers power in more or less the same way.

Depiction of how batteries charge.

Cells consisting of two electrodes (one positive and one negative) and an electrolyte catalyze reactions that convert compounds into new substances. Over time, ions — atoms with too few or too many electrons — form in the electrodes, driving a flow of electrons to the battery’s negative outer terminal and supplying your phone with an electric charge.

In non-rechargeable batteries, those chemical reactions occur only once. But in the rechargeable lithium-ion batteries that power smartphones, the reactions are “reversible.” When the battery discharges, the chemical reaction produces electricity, and when the battery recharges, the chemical reactions absorb power.

Fast charging

So we’ve established how batteries charge and discharge. But to understand how fast charging works, you have to know a bit about something called a charge controller.

A quick side note:

Since we’ll be referring to volts, amps, and watts in the course of our discussion, here’s a refresher. Volts are a measure of voltage, amps are a measure of current, and watts are a measure of electrical power. A common analogy is a garden hose: Volts are equivalent to the water pressure in the hose; the current is equivalent to the flow rate; wattage is equivalent to the volume of the spout’s spray. Watts, then, are the product of volts and amps — volts (V) times amps (A) equals watts (W).

Greater current and higher voltages charge batteries faster, but there’s a limit to what they can take.

Smartphone batteries charge when a current passes through them. Greater current and higher voltages charge batteries faster, but there’s a limit to what they can take. The charge controller (IC) protects against dangerous spikes in current.

The controller chip regulates the overall flow of electricity into and out of the battery. Generally speaking, lithium-ion controllers define the current (in amps) at which the battery charges by measuring the battery’s cell current and voltage and then adjusting the current flowing in. Some use a DC-to-DC converter to change the input voltage, and fancier integrated circuits adjust the resistance between the charger input and the battery terminal to ramp the current flow up or down.

The amount of current the charge controller draws is generally dictated by the phone’s software.

USB charging standards

Voltage Current Max power
USB 1.0 5V 0.5A 2.5W
USB 2.0 5V 0.5A 2.5W
USB 3.0 5V 0.5A/0.9A 4.5W
USB 3.1/3.2 (USB-C + USB-PD) 5-48V 0.5A/0.9A/1.5A/3A/5A 240W
USB4 (USB-C + USB-PD) 5-48V 0.5A/0.9A/1.5A/3A/5A 240W

Unless you’re still rocking a Palm Pilot from the early ’90s, chances are your smartphone recharges via a USB cable. There’s a really good reason: Besides the fact that USB cables are relatively easy to find these days, USB has a really robust, well-defined charging standard called the USB Power Delivery Specification.

USB cable connecting devices.

The USB Implementers Forum specifies several types, one for each corresponding USB specification: USB 1.0, 2.0, 3.0/3.1/3.2, and USB4. USB 1.0 and 2.0 are increasingly rare and incompatible with our modern smartphones. By default, USB 3.0 ports push 5V/0.9A (4.5W).

But by upgrading to the physical USB-C connection (the oval-shaped reversible plug on newer smartphones) and USB 3.1 (and versions after it), PD can become a different animal altogether. It’s technically capable of carrying the USB 2.0 spec, but most manufacturers opt for the latest standards like USB 3.2 or USB4, which can potentially deliver a much higher voltage.

These later USB standards allow devices to take advantage of the USB Power Delivery (USB-PD) spec, which, as of USB-PD version 3.1, has a maximum power output of 48V (240W) charging, although devices tend to stick with the 20V/5A (100W) version for the time begin. Smartphones don’t draw that much power yet — manufacturers commonly stick with a lower amperage (like 3A), but it’s a boon for USB-C laptops like the MacBook Pro and Google Chromebook Pixel.

Slightly complicating things is the Battery Charging Specification, which deals specifically with power drawn from a USB port for charging. The most recent spec, Rev 1.2, defines three different sources of power: Standard downstream port (SDP), charging downstream port (CDP), and dedicated charging port (DCP). CDP, the spec in modern smartphones, laptops, and other hardware, can supply up to 1.5A.

Fully compliant smartphones and chargers respect the limits of USB 2.0 and BC1.2, but not all phones and chargers are compliant. That’s why, generally speaking, smartphones always default to the lowest charging speed.

The USB specs are more like guidelines than dictum, though. Fast-charging standards like Qualcomm’s Quick Charge and Samsung’s Adaptive Fast Charging may exceed the USB spec’s voltage parameters, but on purpose — that’s why your phone is able to recharge in minutes rather than hours.

Fast charging standards: What’s the difference?

USB-PD also only provides the power the device needs, so the same USB-PD charger could charge a smartphone at top speed but then also charge a laptop at its top speed.

Different manufacturers employ the USB-PD standard differently. Here’s how Apple and Google use it, for example.

Apple fast charging via USB-PD

Two iPhones in hands.
Julian Chokkattu/Digital Trends
Voltage Current Max power
USB-PD 14.5V 2A 96W

Pros

  • USB-PD, an industry standard, works with a growing number of devices.

Cons

  • You’ll have to shell out a few bucks to take advantage — Apple doesn’t include USB-PD-compatible chargers in the box for many of its phones.

The USB Power Delivery (USB-PD) standard was developed by the USB Implementers Forum (USB-IF), and it’s a standard that any manufacturer can use on any device with a USB port. It’s capable of delivering up to 100W, so it’s suitable for use with all kinds of devices beyond smartphones, including some laptops, provided they have a USB-C port. USB-PD brings other benefits, too. The direction of the power is not fixed, so you will find portable battery chargers, for example, that have a USB-C port that can be used both to charge another device or to charge the battery pack itself.

Apple iPhones from the iPhone 8 through the iPhone 12 models implement USB-PD, the same industry standard used by the iPad Pro, the 12-inch MacBook, Google’s Chromebook Pixel, and Lenovo’s X1 Carbon. Intercompatibility is its biggest advantage — USB-PD doesn’t require any special cables or wall adapters.

Supported outputs, cables, and adapters

You’ll have to shell out for accessories if you want to take advantage of the iPhone’s USB-PD compatibility because Apple hasn’t packed USB-C cables or adapters in iPhone boxes until recently. You’ll also need to buy a Lightning to USB-C cable that supports USB-PD — if you use a standard Lightning cable with a USB-C to USB-A adapter, the charger will default to the lowest wattage.

Here’s what Apple recommends:

  • Apple 18W, 20W, 29W, 30W, 61W, 87W, or 96W USB-C Power Adapter.
  • A comparable third-party USB-C power adapter that supports USB Power Delivery (USB-PD).

Charging speed

No matter which USB-C charger you buy, you’ll have to put up with hard-coded safety limits in your iPhone. Fast charge kicks in when the capacity is between 0% and 79% but stops when it reaches 80%.

If you don’t mind forking over a few extra dollars for charging accessories, you get much faster charging than you would otherwise. The fast charging iPhones can charge from 0% to 50% in 30 minutes using USB-PD.

Google fast charging via USB-PD

Two Google Pixel phones in different sizes.
Julian Chokkattu/Digital Trends
Voltage Current Max power
USB-PD 9V 2A 18W

Pros

  • The same USB-PD kit will work with a number of devices.
  • Google supplies a fast charging charger and cable in the box.

Cons

  • The top speeds aren’t quite as fast as some other manufacturers offer.

Every Google Pixel phone, from the original to the Pixel 4a, is capable of fast wired charging up to 18W using the USB-PD standard. It doesn’t require any special chargers or cables.

Supported outputs, cables, and adapters

You can use the charger and cable in the box with your Pixel phone to enjoy maximum charging speeds. If you go for third-party accessories, use any USB-C with USB 2.0 power adapters and cables. If you use a USB-C to USB-A cable, then it will charge your Pixel more slowly, regardless of the power adapter you connect to.

Charging speed

A Pixel phone can charge rapidly from 0% up to around 80% but will slow down beyond that point. You’ll find the same limitations with most phones.

Using the cable and 18W adapter supplied or any decent third-party one with a similar or higher rating, you can get seven hours of use from a 15-minute charge.

Qualcomm Quick Charge

Charging a smartphone to 72 percent.
Simon Hill/Digital Trends
Voltage Current Max power
Quick Charge 1.0 5V 2A 10W
Quick Charge 2.0 5V/9V/12V 1.67A/2A 18W
Quick Charge 3.0 3.6V to 20V (200mV increments) 2.5A/4.6A 18W
Quick Charge 4.0+ 5V/9V (USB-PD), 3.6V to 20V (200mV increments) 3A (USB-PD), 2.5A/4.6A 27W (USB-PD)
Quick Charge 5.0 5V/9V (USB-PD), 3.3V to 20V (200mV increments) 3A/5A/>5A 100W+

Pros

  • One of the most widely implemented charging standards.
  • Backward compatible with older versions of Quick Charge.
  • Built-in safety features prevent overheating and short-circuiting.

Cons

  • Quick Charge 3.0 isn’t USB-PD compliant.

Chipmaker Qualcomm’s Quick Charge is one of the most widely implemented charging standards on the market. That’s no mistake — it’s an optional feature of Qualcomm system-on-chip technology, like the Snapdragon 855, 845, 835, 820, 620, 618, 617, 430, and others, which powers phones like the Samsung Galaxy S10, Google Pixel 3, and LG V40 ThinQ. But the technology isn’t tied to Qualcomm’s Snapdragon processors — any smartphone manufacturer is free to license Quick Charge’s power controller technology.

Tech specs and compatible adapters

Quick Charge achieves fast charging by upping the charging voltage, which in turn boosts the wattage. Announced in July 2020, Quick Charge 5 is the latest standard in the series, promising the ability to recharge phones to 50% in five minutes. While support is currently limited to recent phones such as the Samsung Galaxy S20, Quick Charge 4.0+ support is growing in popularity. You can find it in phones like the LG G8 ThinQ, Razer Phone 2, and Xiaomi Mi Mix 3, and it can deliver up to 27W of power.

Quick Charge 4 and newer have the added bonus of compatibility with USB-PD chargers, but Quick Charge 3.0 and older only work with Quick Charge-certified accessories. Still, Quick Charge’s ubiquity means there are plenty to choose from. Qualcomm’s website has a partial list of the most popular options.

Charging speed

Qualcomm claims that Quick Charge 5 can fully recharge smartphones in 15 minutes and take a phone to 50% in just five minutes.

In our testing, Quick Charge 4+ took the Razer Phone 2’s big 4,000mAh battery from 18% to 90% in just over an hour.

Safety measures

Quick Charge’s intelligent thermal balancing moves current via the coolest path, and device sensors monitor the case and connector temperatures to prevent overheating and short-circuiting.

Samsung Super Fast Charging and Adaptive Fast Charging

Inspecting the Samsung Galaxy S10 Plus port.
Julian Chokkattu/DIgital Trends
Voltage Current Max power
Samsung Adaptive Fast Charging 5V/9V 2A 18W
Samsung Super Fast Charging 1.0 11V 2.25A 25W
Samsung Super Fast Charging 2.0 10V 4.5A 45W

Pros

  • Built into all Samsung devices.
  • Adaptive Fast Charging compatible with Quick Charge 2.0 and Super Fast Charging compatible with USB PD.

Cons

  • Tends to be conservative.

Samsung’s Adaptive Fast Charging is exclusive to Galaxy devices. Unlike Quick Charge and other competing fast standards, it’s fully compatible with Exynos, the system-on-chip commonly found in international variants of Samsung’s devices.

Samsung introduced Super Fast Charging with the Samsung Galaxy S10 5G. This phone has a 4,500mAh battery and supports up to 25W charging with the USB Power Delivery 3.0 PPS (Programmable Power Supply) charging standard. The Samsung Galaxy Note 10 Plus hits even higher speeds, using Super Fast Charging 2.0 (as do later models such as the S20 and Note 20). However, to hit the fastest charging it’s capable of requires a special adapter with an unusual 10V and 4.5A rating to output 45W, which means it also requires a 5A cable.

Tech specs and compatible adapters

Samsung’s Adaptive Fast Charging has a theoretical peak of 9V/2A (18W), while Super Fast Charging has a peak of 10V/4.5A (45W) with a travel adapter and 25W when plugged into a normal charger. Both standards tend to be a bit more conservative in practice. Tapping into the highest speeds of either requires buying a certified charger, but most Samsung devices support either Quick Charge- or PPS-compatible accessories.

Charging speed

Samsung doesn’t publish charging times for Adaptive Fast Charging or Super Fast Charging. But in our testing, the Galaxy S8, which has a 3,000mAh battery, took about two hours to fully recharge. The Note 10 Plus took about one hour to fully recharge using the Super Fast Charging standard.

Safety measures

Adaptive Fast Charging technical stats are hard to come by, but anecdotally speaking, it’s on the conservative side. According to XDA’s detailed analysis of fast charging standards, the Galaxy S8 Plus maintains the coolest temperature of any fast-charging flagship on the market.

Motorola TurboPower

Charging a phone with Moto G7 TurboPower.
Simon Hill/Digital Trends
Voltage Current Max power
TurboPower 15 9V/12V 1.2A/1.67A 15W
TurboPower 25 5V/9V/12V 2.15A/2.85A 25W
TurboPower 30 5V 5.7A 28.5W

Pros

  • Built into all Motorola devices.
  • Compatible with Quick Charge 3.0.

Cons

  • Not as fast as some charging standards.

Motorola’s TurboPower standard, a tweaked version of Quick Charge 3.0, ships on Motorola devices like the Moto G Power 2021.

Tech specs and compatible adapters

TurboPower adapters come in three flavors: TurboPower 15, TurboPower 25, and TurboPower 30. The fastest, TurboPower 30, delivers 5V and up to 5.7A for roughly 28.5W of power.

There’s more to TurboPower than the charger. Motorola says it works with manufacturers to design custom batteries and that its power management software monitors battery state and health, then adjusts the incoming charge accordingly.

Much like Samsung Adaptive Fast Charge, you don’t need a TurboPower adapter in order to fast charge a TurboPower-equipped smartphone. Motorola’s charging standard is compatible with any Quick Charge 3.0 (or newer) adapter.

Charging speed

Motorola claims TurboPower 30 can deliver up to 15 hours of battery life in 15 minutes.

Safety measures

TurboPower’s thermal management hardware is designed to avoid charging slowdowns due to heat, Motorola says, and to maintain a steady and fast charging rate.

OnePlus Warp Charge and Oppo VOOC

OnePlus 6T phone perched on table.
Andy Boxall/Digital Trends
Voltage Current Max power
Dash Charge 5V 4A 20W
Warp Charge 5V 6A 30W
Warp Charge 30T 5V 6A 30W
Warp Charge 65T 5V 6Z 65W
Oppo VOOC 5V 5A 25W
Oppo Super VOOC 10V 5A 50W

Pros

  • Keeps phones cooler.
  • One of the fastest charging standards.
  • Adapters included with compatible smartphones.

Cons

Shenzhen, China-based OnePlus licenses Warp Charge (originally called Dash Charge) from Oppo. It’s based on Oppo’s VOOC (Voltage Open Multi-Step Constant-Current Charging) system and is a headline feature in the OnePlus 6T and every other OnePlus phone back to the OnePlus 3. Oppo has also developed the much faster Super VOOC, but it’s only available in a handful of phones like the Oppo RX17 Pro.

Tech specs and compatible adapters

Warp Charge uses a special wall adapter that modulates the amperage in real-time. A microcontroller monitors charge level and syncs with the phone’s circuitry to regulate voltage and current, and a custom-designed cable delivers greater current while minimizing power fluctuations.

All this is proprietary. Warp Charge only works with OnePlus phones and compatible wall adapters and car chargers. Warp Charge-certified external batteries are hard to come by, and OnePlus’ fast charging standard doesn’t work with off-the-shelf USB cables — Warp Charge cables are slightly thicker to accommodate the extra voltage.

You won’t have to shell out extra if you buy a OnePlus phone, though. Every OnePlus smartphone comes with a Warp Charge-compatible wall adapter and charging cord.

Charging speed

We found that Warp Charge proved very effective when charging the OnePlus 9 Pro from zero to 100% in 31 minutes.

Oppo claims VOOC-enabled phones can charge to 75% in 30 minutes. When we charged the Super VOOC system with the Oppo RX17 Pro, it went from 0% to 40% in just 10 minutes.

Safety measures

Warp Charge is designed to dissipate heat quickly. Because the charger transforms the high voltage from the adapter’s power source into a lower voltage, most of the heat from the conversion never reaches the phone, and the consistent current reduces the potential for thermal throttling.

Warp Charge-compatible devices also have heat management and dissipation hardware that undergo a thorough five-point safety check.

Huawei SuperCharge

Two Huawei phones.
Voltage Current Max power
Huawei SuperCharge 4.5V to 10V 4A/4.5A/5A 44W+

Pros

  • Compatibility with USB-PD.
  • Thorough safety measures.
  • Adapters included with compatible smartphones.

Cons

  • Potentially slower than some standards.

SuperCharge, Chinese smartphone maker Huawei’s proprietary charging standard, is built into phones like the Huawei P40 Pro, Huawei P30 Pro, Huawei Mate 20 Pro, and the Huawei P10. It’s a bit like Quick Charge in that it uses higher-than-average voltages to achieve faster charging, but there’s slightly more to it than meets the eye.

Tech specs and compatible adapters

SuperCharge automatically adapts the incoming wall voltage and current based on the condition of the phone’s battery and the phone’s internal temperature. Older SuperCharge-compatible wall adapters and car chargers support three charging modes — 5V/2A, 4.5V/5A, and 5V/4.5A (up to 22.5W) — and use an in-charger chipset to regulate voltage, eliminating the need for heat-producing in-phone voltage transformation. The latest version offers 10V/4A for up to 40W.

Unlike proprietary charging standards like Pump Express and Dash Charge, Supercharge is compatible with USB-PD. That’s thanks to Huawei’s Smart Charge protocol, which intelligently switches between charging modes depending on which charging adapter is plugged in.

Tapping into Huawei’s SuperCharge technology requires buying a compatible wall adapter, but native compatibility with Qualcomm’s Quick Charge standard means any SuperCharge-compatible devices can take advantage of Quick Charge. Every SuperCharge-compatible smartphone comes with a compatible wall adapter.

Charging speed

Huawei’s latest charger claims to support SuperCharge speeds up to 135W, although it has not yet been released, and Huawei is not producing smartphones that can take anything more than around 44W.

Safety measures

The SuperCharge feature, along with Smart Charge, is available on Huawei devices. This unique tool can read whatever charger you’re using and pinpoint its optimal capacity. From there, the tool can modify the charger’s voltage as it needs. 

Producers created SuperCharge with specific design features to carefully control higher currents. Some of those components include an eight-part cooling system and a lining that can keep devices 5 degrees Celsius cooler than other charging methods. Huawei Supercharge devices are built to last, and they’re thoroughly tested to ensure that products meet rigorous safety and performance standards. The company will test their devices in a year-long trial to observe their products under extreme conditions over time.

The future of fast charging

We know this is the understatement of the year, but technology is rapidly evolving. You can bet that fast charging will soon be the universal standard and will likely slowly replace average chargers over the next several years. Thanks to major growth in integrated circuitry, charge controllers, adapters, and cords, phones could soon potentially recharge over the span of just a few minutes instead of several hours. Early-model fast chargers recently gained popularity for their promises to increase your device’s portability and charge quickly.

As this technology evolves and becomes more accessible, fast charging will only continue to grow and improve with manufacturing. Current prototypes boast incredible speeds, such as Xiaomi’s claim that its HyperCharge technology can charge a 4,000mAh battery in eight minutes, but we’ll learn more about new standards as they are fully developed and appear in the market.

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