see also:

• photography and camping main index page
• 12V batteries and battery boxes
• DC power supplies
• https://en.wikipedia.org/wiki/USB
• Aust. product safety recalls of USB power banks that can explode - as of July 2025 includes:
  • Anker Power Bank Model: A1257, A1647, A1681, A1689, SnapWireless PowerPack Slim (Gen 1), Anker power bank A1647, Baseus magnetic wireless charging power banks 6000mAh 20W, Cygnett MagMove 5K Power Bank; Baseus power bank 65W 30000 mAh (model number: BS-30KP365), Quad lock MAG battery pack and BoostCharge Pro fast wireless charger for Apple watch + power bank 10K, and several from Comsol, Lenovo and Kogan

• Universal Serial Bus (USB) is an industry standard 1st introduced in 1996, for hot-swappable (do not need to reboot the computer to plug in) power supply and data communication which replaced the previously ubiquitous RS serial ports and cables. Microsoft Windows 95, OSR 2.1 provided OEM support for USB devices in August 1997.
• unfortunately with the variety of connector types and protocols now available it has become a major source of frustration, particularly when you also start to add in Apple Lightning and Thunderbolt connectors (Thunderbolt 3 uses the USB-C connector) and similar.
• European Union has announced in 2021 it will ban devices being sold which are not USB-C compliant within the next 2 years or so in an attempt to unify the situation, reduce confusion and waste. Thankfully, Apple has now replaced its proprietary Lightning connections with USB-C in all of its latest model phones and iPads.

• by design, it is difficult to insert a USB plug into its receptacle incorrectly
• some computer USB ports supply power to power USB devices.
  • most of these supply power at 5V ± 5% and devices may draw loads as follow:
    • low power device: 100mA/0.5W (USB3 150mA/0.75W)
    • high power device: 500mA/2.5W (USB3 900mA/4.5W)
    • battery charging devices: 1.5A/7.5W (v1.2: 5A/25W)
      • Quick Charge (QC) 18W max usually
    • Power Delivery (PD) 20V port: 3A/60W micro-USB (5A/100W USB Type A/B or USB-C 2.0/3.0)
    • Power Delivery (PD) 48V port: 5A/240W USB-C 3.1
• USB-A
  • this is the standard, original PC connector and it has a large white connector with 4 pins (1 power VCC, 2 central data pins D+ and D-, 1 GRD)
  • it is designed for USB 1.x and USB 2.x protocols with speeds up to 480Mbits/sec (ie. up to 50Mb/s)
• USB-A super speed USB 3.x
  • this is same physical size as USB-A but has a blue connector instead of white, 5 additional pins (TX1+, TX1-, RX1+, RX1- plus extra GND) and supports USB 3.x as well as older USB protocols, and when connected to a USB 3.x Gen 1 device allows data at up to 5GBits/sec (ie. ~500Mb/sec) and when connected to a USB 3.x Gen 2 device allows data at up to 10GBits/sec (ie. ~1Gb/sec)
• USB Quick Charge (QC)
  • pre-PD enhanced charging protocols usually limited to 18W
  • a Qualcomm proprietary technology that allows for the charging of battery-powered devices using USB connections at higher than 10W - see https://en.wikipedia.org/wiki/Quick_Charge
• USB-B
  • these are square versions of the USB-A including a super speed version with a second input for the extra 5 pins
• USB-C
  • fantastic but highly variable and can be problematic as there are many differently wired cables and most do NOT WORK fully!
    • many cables may only do USB2.0 data transfer speeds and may only support 5V legacy charging and some may not do any data transfer
    • high charging PD cables generally need a thicker cable but may have poor data transfer speeds
    • high data transfer speeds generally need a thicker cable but may not have high PD charging rates
    • to protect batteries, use slower USB-A charging when possible and only do fast charge if you really need it - and don't use it on legacy devices that cannot take high charging rates safely
  • these are small, flat connectors with 24 pins and compatible with USB 2.x and USB 3.x to give speeds up to 20Gbits/sec (ie. ~2Gb/sec) if Gen 2×2 USB and with eMarker chip, and also compatible with USB 4.x developed in 2019 (Thunderbolt 3 and 4) which allows up to 40Gbits/sec (ie. ~4Gb/sec), while USB4v2 doubles the data transfer again, and as it can be inserted “upside down”, some pins are duplicated
    • A1 GND, A2 TX1+, A3 TX1-, A4 VBUS, A5 CC1, A6 D+, A7 D-, A8 SBU1, A9 VBUS, A10 RX2+, A11 RX2-, A12 GND
    • B1 GND, B2 RX1+, B3 RX1-, B4 VBUS, B5 SBU2, B6 D-, B7 D+, B8 CC2, B9 VBUS, B10 TX2+, B11 TX2-, B12 GND
  • GND, 5V VBUS, D+ and D- data provide compatibility with USB-A 1.0 and onwards
    • on USB-A, QC 18W charging is provided through D+ and D-, but on USB 3.0 onwards QC is usually via CC1 and CC2
  • TX1 and RX1 pairs were added to USB 2 to give increased data transfer rates
  • TX2 and RX2 pairs were later to USB 3 to give further increased data transfer rates
  • CC1 and CC2 were added in USB-C for PD power and added to detect orientation of connector and negotiate PD role, voltage and current
    • USB-C allows Dual Role Power (DRP) as it can act as either downstream facing port (DFP) or upstream facing port (UFP) for power delivery (analogous to OTG USB-A for data)
    • you can no longer use use a simple multimeter to ascertain what is happening but can use devices such as ChargeLab PowerZ KM003C which supports PD 3.1 and provides Windows software to analyze what is going on in the CC data transfers as well as checking for eMarker compliance or you can connect the CC pins to oscilloscope probes ¹⁾
    • on connecting a device to a power bank or charger, the source announces its voltage capabilities, then a request for a voltage and current is requested
    • if two charging devices are connected, they may have a factory or software defined preference setting of either giver or taker, or, the charge direction may end up being random
    • most USB hubs or charging docking stations are UNI-DIRECTIONAL for charging!
    • only cables with E-Marker can do above 60W PD and/or 20Gbit/sec or higher data transfer
  • SBU1 and SBU2 were added to provide alternate standards for video and audio eg. HDMI
  • to save cost, some USB-C cables may not connect all pins and some do not have the required two pull down 5 kOhm resistors on female connections (which means no charging will occur if these are not present) creating power charging incompatibilities and may only support 5V legacy mode, while thin cables may only support USB-A data transmission rates and may overheat with higher PD voltages!
  • this connector should supercede most other if not all USB connectors and unlike previous connectors the cable is reversible
  • USB-C support PD charging, data transfer, audio, video, Thunderbolt mode, and daisy chaining
  • the PD also supports Programmable Power Supply (PPS) for dynamic voltage changes - some smartphones use this to optimize charging
  • some “PD” chargers are fake and only provide legacy 5V charging
  • some devices are NOT designed for the high PD charging rates and do NOT have protections such as a PD CH224 controller chip to stop you charging them at excessive rates which may cause damage to their lithium ion batteries - these usually have USB-A mini or micro ports but these won't stop you using a USB-C cable with an adapter!
• USB mini connectors for the device end
  • these are 6.8mm wide and come in 3 main types for USB2.x (each with 5 wires):
    • Mini A
    • Mini B
    • Mini AB
• USB micro connectors for the device end
  • these are 6.8mm wide and come in 3 main types for USB2.x (each with 5 wires) and each have wider superspeed USB 3.x versions with 10 wires:
    • Micro A
    • Micro B
    • Micro AB

• USB device communication is based on pipes (logical channels) which are connections between the host and the logical connection in a device - each USB device can have up to 32 endpoints (16 in and 16 out), though it is rare to have so many.
• The functionality of a USB device is defined by a class code sent to a USB host eg. audio, printer, etc

• note despite the below, some manufacturers paint their USB ports for fashion and thus not to indicate functionality!!
• white - USB 1.x released 1996 - up to 12Mbps data but data could only go in one direction
• black - USB 2.0 released 2000 - up to 480 Mbps data but data could only go in one direction
• blue - USB 3.0 released in 2008 - up to 5Gbps and can send and receive data simultaneously
• teal - USB 3.1 Gen 1 released in 2013 - up to 10Gbps
• red - USB 3.1 Gen 2 or USB 3.2 - released in 2017 - up to 20Gbps, adds always on, charge and sleep feature (although this depends upon manufacturer as to if it is enabled)
• yellow - USB 2 standards but always on for power
• orange - USB 3.0 standards but always on for power

• these are proprietary and have a chip in the end of the cable which dynamically assigns roles to each of its 8 pins and then internally maps these to USB - which is mainly USB 1.0 but may have USB-C pins such as CC, etc.
• these have been replaced by USB-C following demands from the European Union to simplify cabling - since the Apple devices are USB-C and not Lightning
• unless you get a special adapter such as “Lightning to USB 3 Camera Adapter”, Lightning cables are confined to USB 2.0 speeds of 480Mbps even if they have USB-C connection