💾 Archived View for pwshnotes.flounder.online › gemlog › 2023-10-13-usb-charging.gmi captured on 2024-05-26 at 14:33:07. Gemini links have been rewritten to link to archived content
⬅️ Previous capture (2023-11-04)
-=-=-=-=-=-=-
I collect high quality flashlights (torches) as a hobby. And, as a result, I've been trying to make sense of the USB charging standards. What I found was confusing and, frankly, not standard. Here's what I found.
The oldest voltage and amperage standard for USB is 5 volts and 500 milliamps or 0.5 amps.
This is just meant to power a keyboard or mouse. And, it is not really useful for charging modern devices.
As far as I can tell, the next most relevant standard for charging is a de facto standard that Apple created. Some older Apple chargers and Apple devices (iPhone, iPad) would support charging at up to 10 watts. This is commonly referred to as "iPad compatible" or "5V/2A".
While I found charging at 10W referred to as "USB standard charging", there is no 5V/2A USB standard as far as I can tell. Instead, this charging scheme is something Apple developed.
The next most relevant standard is Qualcomm's proprietary Quick Charge standard. This is common on Android phones. And some flashlights explicitly support QC. The device and the charger both explicitly have to be QC for this to work.
One important warning is that QC 4 is not backwards compatible. So, you might want to choose QC 3, QC 4+, or QC 5 chargers which are backwards compatible. The QC 4+ standard appears to have fixed the compatibility issue from QC 4.
Something else to watch out for are chargers with multiple ports. Cheaper chargers will only support Quick Charge on one port while the other ports will be 5V/2A. Make sure to check how many charging ports support QC if you intend to charge multiple Quick Charge devices at the same time.
I want to buy a new charging cable. But, I wasn't sure what the cable requirements are for Quick Charge. From the Qualcomm FAQ:
Q: Does it matter what type of charging cable is used with a Quick Charge adapter?
A: Quick Charge is designed to be connector- and current-independent. ... Quick Charge high-voltage operation is designed to minimize charging issues associated with long or thin cables, allowing for a superior charging experience, independent of cable type or cable current capability.
That's not very precise. And, it leaves a lot of room for misinterpretation and poor consumer experience.
After shopping for a while, I did find a few references to either Quick Charge or the charging capacity in watts claimed by the cable manufacturer. But, these claims seemed dated: reflecting the dates when these products came on the market. It doesn't seem like much attention is paid to whether or not a particular cable is Quick Charge compatible. And, Qualcomm's data doesn't allow cable manufacturers to give a definitive answer like "This cable is compatible with QC 3.0."
My best guess is that most cables will support Quick Charge. And, if you spend more than $10 on a cable then you should be fine. But, that dollar amount is arbitrary; I based it more on reviewers who said their cheap cables fell apart than anything to do with charging.
Update: I bought a combination cable with three different ends--USB-C/Micro USB/Lightning--so I could also charge some old devices without swapping the cable. The product description reads "Compatible with fast-charging devices." I'm not sure about 5V/2A. But, I am not able to Quick Charge over the cable. My TM9K TAC will indicate when it is fast charging. But, it indicates slow charging while connected to a Quick Charger over this cable. I probably need a normal USB-A to USB-C cable for Quick Charge. So, watch out for these non-standard multi-cables.
Eventually, the USB Implementers Forum standardized charging with "USB Battery Charging". This charging standard does not appear to be used much because I never heard of it before today. Also, it is capped at 7.5W which can't quickly charge the high capacity batteries commonly used today.
USB Power Delivery doesn't appear to be relevant for charging mobile devices or flashlights. It supports much higher wattages (100W). I have not seen any mobile devices say they are compatible with USB-PD. And it seems mostly aimed at either charging laptops or providing wire line power for monitors or external hard drives which would otherwise need a separate power cable.
As a further wrinkle, all my lights shipped with a USB-A to USB-C charging cable. And they can charge at full speed with those cables.
While I don't charge with a C-to-C cable, many people have reported that charging with a USB C-to-C cable doesn't work. So, device compatibility with a C-to-C cable is something you have to check for before you buy.
If you are purchasing a charger, I would stick with chargers that provide USB-A ports as those seem to be the most compatible.
While researching chargers, you might see the term "GaN" used. Gallium nitride (GaN) chargers use a newer technology that lets them operate at a high wattage while remaining cool. GaN chargers are superior to older silicon chargers. But, you don't need to replace your charger if you don't want to. GaN is a nice upgrade, but it is not required especially if you already have a charger that is compatible with your device.
To make sense of this, let's take a look at my three lights.
One light says it supports 5V/2A charging.
One light says it supports QC 2.0, QC 3.0, or 5V/2A. and
One light says it supports "QC" or 5V/2A.
The "5V/2A" corresponds to that Apple de facto charging standard and will work with chargers that either explicitly list "5V/2A" or that make some comment about being Apple or iPhone/iPad compatible. So, I can charge all these lights with an Apple compatible charger since they all list 5V/2A as an option.
It was a relief to read "QC 2.0 and QC 3.0" compatible because that was the clearest claim I read today. That light is compatible with those standards. Just make sure the charger is not using QC 4 because that standard is not backward compatible. I would use a QC 3, QC 4+, or QC 5 charger with this light.
The final light doesn't specify which Quick Charge standard it is compatible with. Realistically, the light probably can't charge faster than QC 2 or 3. So, I would look for a QC 3 charger to pair with this light.
That's it. I hope this clears up some of the confusion around phone (and flashlight) charging.
Lights that do/don't support C-to-C charging | Reddit
USB-C to USB-C Charging Cables | Stack Exchange
What Is a GaN Charger, and Why Will You Want One? | How-To Geek
Created: Friday, October 13, 2023
Updated: Friday, May 24, 2024