Long-term experiences in USB charging: USB-PD, Qualcomm Quick Charge & Apple
There are many USB fast charging protocols out there. In this overview and intro I explain how to categorize, understand and use them. I have to travel with my professional audio, video and recording equipment a lot. Here is my report after using over 100 chargers and different charging equipment for multiple years.
Intro: why you want other chargers
As readers of this blog know: I am working remotely, traveling a lot, and professionally serving clients in photography and technology prototyping all over the world. Some of my equipment is stationary, and I usually leave it with friends, maker spaces, or other places. You can read my suggested gear for the nomad nerd, where I am keeping track of some of the devices and things I have reviewed and tested throughout the years.
I get asked a lot:
“Why do I need another charger? Why can’t I just use USB ports on the computer, or any power strip with USB-A or USB-C to charge my devices”
Well, the answer is quite simple: most power strips don’t support fast-charging standards such as Qualcomm’s Quick Charge or USB Power Delivery (USB-PD). So your devices will load very slowly, which is not feasible if you are a photographer, audio producer or podcaster. Hell, even for a normal consumer faster charging devices are essential. As professional I ended up with missing or broken chargers a lot. So understanding the technology behind becomes a necessary trait to use other devices, to repair or to hack them together if needed. This often saved my day, or gig for that matter.
Standard USB ports and their maximum power output
When you are charging your devices from standard USB ports (for example from your laptop) — you should keep in mind the maximum output supported from the types of USB ports.
The maximum power output supported by USB ports varies by the version of the USB standard:
- USB 1.0/2.0 port: Typically up to 2.5W (5V, 0.5A)
- USB 3.0/3.1 ports: Up to 4.5W (5V, 0.9A) for standard ports, and up to 100W (20V, 5A) for ports supporting the USB Power Delivery (USB-PD) specification.
- USB-C is a connector type, and does not tell anything about the USB version used. USB-C offers a broad range, supporting USB Power Delivery (USB-PD) with power levels up to 100W (20V, 5A). The lowest possible power output from a USB-C connector, adhering to the USB 2.0 standard, is 5V at 0.5A, equating to 2.5W.
The USB-C connector is designed to be universal, replacing older USB connectors and the Mini DisplayPort connector. It supports various protocols, including USB at all speeds, Thunderbolt (version 3 and later), and DisplayPort (version 1.2 and later), among others. It’s crucial to differentiate between the connector type (USB-C) and the protocols (like USB, Thunderbolt, DisplayPort) that run over it, as the connector itself is just a physical interface.
USB 3.0 and 3.1 are iterations of the USB standard that offer increased data transfer speeds compared to their predecessors. USB 3.0, also known as USB 3.1 Gen 1, provides speeds up to 5 Gbps, while USB 3.1, or USB 3.1 Gen 2, doubles that to 10 Gbps. The USB-C connector can support these speeds and more, making it a versatile choice for data transfer, power delivery, and video output. USB-C is not limited to a specific USB version, allowing devices to use the connector with USB 3.0, 3.1, and other protocols for maximum compatibility and performance.
The situation with power strips
Power strips with USB can be a convenient solution for charging multiple devices, but they may not be ideal for everyone due to several limitations:
- Limited fast-charging capabilities: While some newer power strips offer USB-C ports with Power Delivery (PD) or Quick Charge (QC) for faster charging, not all do. Many still provide only standard USB-A ports with limited power output (5W or 10W), resulting in slow charging times compared to dedicated chargers.
- Lower power output: Even power strips with PD or QC capabilities often have lower wattages compared to dedicated chargers, especially GaN chargers. This translates to slower charging, particularly for devices that support higher wattages.
- Safety concerns: Using low-quality power strips with USB can pose safety risks, such as overheating, electrical overload, or even fire hazards. It’s crucial to choose power strips with proper safety certifications and reputable brands.
Here is an example of a power strip with USB plugs — which is very popular on Amazon. You have to be very careful with these! Always read the specifications. For this specific one: USB A ports (5V/2.4A) and USB C ports (5V/3A) max for each port. (3.4A/17W in total — which can be considered “fast charging”). I do not recommend any of these power strips at all!
The rare case of USB-PD power strips — and why price does not tell you anything about the quality
Power strips with USB Power Delivery are getting more frequent. A few years ago these have been outliers, but now you can find them — and there is a reasonable amount of experience and reviews about them out there. But be careful! Take this example: the HANYCONY USB C Charging Station with Surge Protection. This one has almost 35,000 5-star reviews on Amazon.
Always read the negative reviews first, and rank them higher than positive ones. In this case user Anaeee on Amazon reported different specs, and no surge protection.
Another rule of thumb is: never judge on price or materials alone. Here is an example of a review from user PandaMaster on Amazon critisizing the Austere VII Series Surge Protector Power Strip, 6 Wide Outlets, 3 USB C & 2 USB A 2.4 amp Ports, 45W Power Delivery. This one is higher priced (ca $200) and features a heavy duty metal case.
The solution is to DYOR: do your own research. I have compiled an overview so you can save time.
An overview of charging protocols
In general, the industry considers chargers with 10W or more output as “Fast chargers” or “Quick Chargers” (which equals 2.0A at 5V output, the typical voltage of USB).
Categorizing fast charging: 4 broad categories
Fast charging is easy to understand — but the naming is a mess (similar to the USB confusion and the recent USB4 Version 2.0 introduction. We can’t have nice things). Here is a categorization, as smartphone manufacturers have produced different charging protocols over time.
- Samsung and Qualcomm technologies, which are widely used across the mobile industry except by Apple.
- USB Power Delivery (USB PD), an open standard that’s also supported by a wide range of devices including those from Google and others.
- Apple’s proprietary fast charging, which is specific to Apple devices.
- Everything else.
Generally, all these fast charging solution exceed the output of 10W by allowing the device to negotiate a different voltage with the charger (i.e. moving up from 5V to 9V). These fast charging solutions have all been invented to make smartphones and tablets charge quicker.
Samsung and Qualcomm technologies
Samsung devices are almost 100% compatible with QC-enabled chargers
- Samsung Adaptive Fast Charging (AFC) is a proprietary fast-charging technology developed by Samsung for its smartphones and tablets. It utilizes a higher voltage and amperage compared to standard USB charging, enabling faster charging speeds. Super Fast Charging is a marketing name for USB PPS. PPS stands for “Programmable Power Supply” and is an optional part of USB PD 3.0 and USB PD 3.1 (link to discussion)
- Super Fast Charging (SFC) is a term used by Samsung for their faster-than-average charging technology implemented in many of their smartphones and tablets. Samsung calls it “an evolution of the earlier Adaptive Fast Charging (AFC)”, and it actually offers even quicker charging speeds. Samsung Super Fast Charging guarantees 25W of peak charging power, with potential to go beyond (source). Super fast charging 2.0 (as in the Samsung Galaxy S24) supports 45W peak charging. To make this tangible: the Samsung S23 Ultra charges in 57 minutes using a 45W adapter, but does not use continuous 45W (see the report on actual wattage used). The Samsung Galaxy S24 Ultra supports actual 45W wired fast charging (source) — that is 60.6 mAh per minute.
Qualcomm Quick Charge
Quick Charge (QC) is a proprietary battery charging protocol developed by Qualcomm, and the technology supports various power levels depending on the version. Quick Charge versions range from 1.0 up to 5, with the latest versions (like Quick Charge 4 and 4+) supporting up to 100W of power delivery. This technology enables faster charging times for compatible devices by increasing the power transfer compared to standard USB charging. You can read Qualcomm’s patent ‘High Voltage Dedicated Charging Port’ for more details. QC has been reverse engineered by Robert Nixdorf in 2017, and there are details on how to build a simple circuit with QC 2.0/3.0 on hackster.
Introduced in 2013, Quick Charge 1.0 marked the beginning of Qualcomm’s fast charging technology, supporting up to 10W of power. Following this, Quick Charge 2.0 was released in 2014, increasing the power output to 18W and introducing features like High Voltage Dedicated Charging Port (HVDCP) and optional Dual Charge.
Quick Charge 3.0 launched in 2016, and further improved the charging process by offering up to 36W of power to introduce more refined voltage adjustments and battery saver technologies. In 2017, Quick Charge 4 was introduced, supporting up to 100W via Qualcomm’s implementation and 27W via USB Power Delivery, including features like HVDCP++, Dual Charge++, and compatibility with USB PD.
tldr; Qualcomm Quick Charge QC 4 and 5 are compatible with USB-PD
Qualcomm Quick Charge 5 (2020) supports over 100W of charging power, enabling a smartphone to charge from 0% to 50% in 5 minutes. Quick Charge 5 is designed to be backward compatible with previous versions and works with USB Power Delivery (USB-PD) standards.
Trivia: Google Pixel phones do not support Qualcomm’s Quick Charge technology. While some Pixel models use Qualcomm Snapdragon processors that are capable of Quick Charge, Google has opted to use the USB-C Power Delivery (PD) standard for fast charging instead.
Everything else
There are so many other charging protocols. For sake of completeness, I aim to maintain a somewhat complete list of charging protocols that are a) compatible with QC, and b) other (possibly incompatible). Please check the Wikipedia page titled “Quick Charge”, where I am also contributing updates.
Compatible with QC: Asus BoostMaster, Vivo Dual-Engine Fast Charging, Xiaomi Mi Fast Charge, Motorola TurboPower.
Other (potentially incompatible): Realme DART, MediaTek Pump Express, Vivo Super Flash Charge, Huawei SuperCharge, OPPO SuperVOOC, VOOC, Warp Charge / Dash Charge (Oneplus; similar to SuperVOOC) and Infinix XCharge.
USB Power Delivery (USB PD)
USB-Power Delivery (PD) is a fast-charging technology based on the USB -C standard. Is is an open standard that’s also supported by a wide range of devices.
The USB Power Delivery specification is available from usb.org, and is currently available in version 3.2 (10/31/2023) with the complete title USB PD R3.2 V1.0. The contributor list is impressive (see page 3 of the spec document), and lists companies such as Apple, Foxconn, HP, Huawei, Infineon, NXP, Samsung, Seagate, Texas Instruments, Western Digital, and many others.
Introduced in 2012 by the USB promoters group, the first USB-PD specification extended “certified PD aware” USB cables with standard USB Type-A and Type-B connectors to deliver increased power (more than 7.5 W maximum allowed by the previous USB Battery Charging specification) to devices with greater power demands. USB-PD A and B plugs have a mechanical mark while Micro plugs have a resistor or capacitor attached to the ID pin indicating the cable capability. Generally (as visible in the following image) any USB-C cables are good unless you want to charge more than 3A or more than 60W.
Hackaday is a good source if you want to read more background about USB-C: Power Delivery, and Arya’s point is that USB-PD generally is good for the planet, because 1) it eliminates proprietary barrel plug chargers that we’ve been using for laptops and myriads of other devices, and 2) 20 V-capable chargers also have to support 5 V, 9 V, and 15 V as well in practice. This all converges to less electronic waste, and results in reusable technology. (source)
There’s little technical reasons that a switch-mode power supply has to be hard-wired to a certain voltage, and USB-C breaks these chains. Now, you can get 9 V or 20 V at 3 A from a gas station charger and a small cheap board, and you can even charge Li-Ion batteries from a PPS charger. There’s a potential in USB-C capabilities, that we’re only now starting to tap into. As times goes on, proprietary plug and wacky voltage chargers around us will completely die out, and we’ll forget about them, just like we’ve forgotten about all the cellphone data transfer cable standards after MicroUSB took over. How many proprietary data cable ports did Samsung alone create, again? (Source: hackaday)
If you are shopping for USB cables: the USB Implementers Forum (or USB-IF) invites USB-C cable manufacturers to put their cables through compliance testing (see: USB Power Delivery Compliance Test Specification). Those who do the testing get a logo for their packaging — which lets you know what kind of charging power and data transfer speeds you can expect.
When shopping for a cable, try and see if the manufacturer or mentiones being certified by USB-IF. Search for “USB-IF Certified”. More information about the Certified USB Logo Program announcement website.
“ Stick to AmazonBasics, Anker, Cable Matters, Monoprice, Nekteck and all will be good.” (chx in r/UsbCHardware)
Apple’s proprietary fast charging protocol
Apple has their own thing going, and when it comes to their protocols — they are only available if reverse engineered. The Apple Lightning connector was quite a beast, and the interface was “cracked” in 2015.
Tom Roth (aka stacksmashing) did a lot of reversing and documenting Apple’s protocols, and you can watch his talk “Inside Apple’s Lightning: JTAGging the iPhone for Fuzzing and Profit” on YouTube.
Apple’s proprietary fast charging technology has evolved over the years, incorporating various standards and connectors to enhance the charging speeds of its devices. Starting with the iPhone 8 and later models, Apple introduced the capability to fast charge these devices up to 50% battery in around 30 minutes. This fast charging is enabled through the use of a USB-C to Lightning cable combined with specific Apple USB-C power adapters or comparable third-party USB-C power adapters that support USB Power Delivery (USB-PD). The compatible power adapters range in wattage from 18W to 140W.
Apple’s Lightning connector, introduced with the iPhone 5 and used up until the iPhone 14 series, represents a significant part of Apple’s approach to charging and data transfer. The Lightning connector is reversible and supports USB 2.0 for most devices, with certain iPad Pro models supporting USB 3.0 (now USB 3.2 Gen 1) for higher transfer speeds. The Lightning connector also includes an authentication chip to regulate third-party accessory compatibility, highlighting Apple’s control over its ecosystem.
In June 2022, the European Union passed a law requiring all devices to be compatible with a USB Type-C charging port by late 2024, arguing that it will reduce electronic waste and save money for consumers. Apple had contested the law as unnecessary but later put USB-C connectors in iPhones to comply with EU rules.
With the information learnt here you can buy certified cables that are cheaper than Apple’s own cables. A very good and recommendable cable for Apple hardware (monitors for example) is the Satechi Certified USB C Thunderbolt 4 Cable (3.2ft/ 1M), 40Gbps Data Transfer, 240W PD.
Gallium Nitride (GaN) technology
Gallium Nitride (GaN) technology represents a significant advancement in power electronics, particularly for charging devices. GaN chargers are more efficient and compact compared to traditional silicon-based chargers.
GaN is just a material that is used instead of silicon to allow chargers to be smaller and more efficient.
But there are also disadvantages of GaN over Silicon: in a longer discussion on Quora, material scienist Aniruddhan Gowrisankar discussed that “GaN as a material has a lot of serious issues that do pose a challenge”. If you want to dig deeper into GaN I can recommend the following papers
- Matteo Meneghini, Carlo de Santi, Idriss Abid, Matteo Buffolo, Marcello Cioni, et al.. GaN-based power devices: Physics, reliability, and perspectives. Journal of Applied Physics, 2021, 130 (18),
pp.181101. 10.1063/5.0061354. hal-03421528 - GaN introduction, devices basics and applications (Fred Yue Fu, Co-founder GaNPower international)
Suggestions on upping the USB-PD charging game
Unplug chargers and cables when not needed. The output of some chargers reduces when multiple USB C ports are connected even when one of the cable on the charger side has no device connected to it (source). This can be due to the cables being “active cables” (Apple!), or sometimes there might be a flaw in the circuit that prevents charging on the USB-A ports. A user on Amazon reported “to restore the charging capability of the Type-A ports, the unit must physically be unplugged from the wall outlet, allowed for the residual power to dissipate, and be plugged back into the wall outlet”. This might be caused through resistors in the USB cables — or potentially flawed circuits. In any case, unplugging the chargers and cables when not used will extend the life of your product.
Use good chargers with high efficiency. If you have a basic understanding of electronics: read teardown reports (here is a great example). Find reproducible technology and chargers other people tested. A good metric to keep track of is the PQS (power quality score). Baseus, Anker, Ugreen and Satechi are good brands, but you have to check for every device individually. I am recommending Satechi 108W Pro USB C PD Desktop and Baseus 100W PD GaN3 Fast Wall Charger.
Use proper USB-C cables that are USB-IF certified. I can not stress this enough. Most of the issues people are reporting are because they are using the wrong cables. Using the wrong cables can destroy the logic of the charger, or burn down your house. Suggested cables:
- USB-IF Certified Cable Matters 10 Gbps Gen 2 USB A to USB C Cable
- Cable Matters [USB-IF Certified] 240W USB C Cable
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