There is a huge variance,
then, between normal USB ports rated at 500mA and dedicated charging
ports which range all the way up to 3,000mA. This leads to a rather
important question: If you take a smartphone which came with a 900mA
wall charger, and plug it into a 2,100mA iPad charger, as an example,
will it blow up?
In short, no: You can plug any USB device into
any USB cable and into any USB port, and nothing will blow up — and in
fact, using a more powerful charger should speed up battery charging.
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.
Way back in 2007, the 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. Shortly thereafter, USB devices that implemented
this spec started to arrive.
If you have a modern USB device —
really, almost any smartphone, tablet, or camera — you should be able to
plug into a high-amperage USB port and enjoy faster charging. 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. In some (much
older) cases, USB devices can only be charged by computers with specific
drivers installed.
There are a few other things to be aware of.
While PCs can have two kinds of USB port — standard downstream or
charging downstream — OEMs haven’t always labeled them as such. As a
result, you might have a device that charges from one port on your
laptop, but not from the other. This is a trait of older computers, as
there doesn’t seem to be a reason why standard downstream ports would be
used, when high-amperage charging ports are available. Numerous vendors
now put a small lightning icon above the proper charging port on
laptops, and in some cases, those ports can even stay on when the lid is
closed.
In a similar vein, some external devices — hard drives
and optical drives, most notably — require more power than a USB port
can provide, which is why they include a two-USB-port Y-cable, or an
external AC power adapter. Otherwise, USB has certainly made charging
our gadgets and peripherals much easier than it ever has been. And if
the new USB-C connector catches on — and it looks like it will — things
will get even simpler, because you’ll never again have to curse after
plugging it in the wrong way.
