Google extremetech.com and androidexchange for further information.
In a nutshell, to answer your questions, (based on expert or user opinions on these websites):
In general, there are two key factors that affect how quickly your device charges over USB: (1) The maximum amperage of the USB socket, powerbank or wall charger, and (2) how your device negotiates power delivery from the socket/charger.
As for (1), Not all USB chargers, connectors, and cables are born equal.
For a start, every charger or socket has a max amperage — usually between 500 milliamps (mA) and 1.5 amps (A). In general, unless it says otherwise, your laptop and PC are probably outfitted with 500mA sockets (unless they’re USB 3.0, in which case they’re probably 900mA). Specifically, USB 2.0, in terms of actual current (milliamps or mA), there are three kinds of USB port dictated by the current specs: a standard downstream port, a charging downstream port, and a dedicated charging port. In the USB 1.0 and 2.0 specs, a standard downstream port is capable of delivering up to 500mA (0.5A); in USB 3.0, it moves up to 900mA (0.9A). The charging downstream and dedicated charging ports provide up to 1500mA (1.5A). There is also USB chargers that provides 2.1A at 5V.
For [B]cables and connectors, the inside pins carry data (D+ and D-), and the outside D- (date minus) pins provide a 5-volt power supply. You've heard of Apple usb cables that melt and burn? V = IR, the cables are not rated to handle the high 2.1A at 5V
The longer answer is that the age of your device plays an important role, dictating both how fast it can be charged, and whether it can be charged using a wall charger at all
In 2007, USB Implementers Forum released the Battery Charging Specification, which standardized faster ways of charging USB devices, either by pumping more amps through your PC’s USB ports, or by using a wall charger. USB devices post 2007 should follow this spec. Modern devices with this spec can be pluged into a high-amperage USB port and enjoy faster charging. On the other hand, if you have an older device, however, it probably won’t work with USB ports that employ the Battery Charging Specification; it might only work with old school, original (500mA) USB 1.0 and 2.0 PC ports
As for (2),
The max amperage dictates one thing only: The max theoretical charging rate of your device. It is through negotiation that your device actually decides how much power it wants to draw from your power source, e.g. powerbank. When you plug your device into a charging socket or wall charger, the USB controller in your device talks to the USB controller attached to the socket/wall charger — or, if no controller is available, the device reads the voltage flowing across the four USB pins. From this data, your device decides how much amperage to draw, and thus how quickly it will recharge.
Hope this is informative enough,
newbie alert, forgive me if I did not follow forum conventions
when2meets2boy
QUOTE(nordingh @ May 15 2015, 10:19 PM)
I bought USB cable with the Volt and Ampere display from Aliexpress to test output from various USB port.
When no phone connected, it's will show the Volt. When phone is charging, the display change to the current Ampere from USB to the phone.
So far, most powerbank only can give 1.0 - 1.3Amp even use 2.1 Amp output slot. Tested using Yoobao, Xiaomi, Enerpad and Pineng. and also some cheap PB.
[attachmentid=4449372]
This post has been edited by when2meets2boy: Oct 18 2015, 04:50 PMWhen no phone connected, it's will show the Volt. When phone is charging, the display change to the current Ampere from USB to the phone.
So far, most powerbank only can give 1.0 - 1.3Amp even use 2.1 Amp output slot. Tested using Yoobao, Xiaomi, Enerpad and Pineng. and also some cheap PB.
[attachmentid=4449372]
Oct 18 2015, 04:47 PM

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