36 25 May – 7 June 2022 • Issue 632
As shown by the green bars, our iPhone went
from empty to a full charge in a little over an
hourWe ran our tests using Anker's £29.99
PowerWave Dual Base chargerHow I use wireless chargers
How do you use wireless charging?
Please let us know: [email protected]I have two wireless chargers: one beside the bed, and one on
my desk. I use them to charge a Google Pixel 5 phone, and also
a pair of Google Pixel Buds that need turning upside down on the
bedside stand to align the case’s internal coil with the charging
coil in the stand. Sadly, my car is 2010 vintage, which not only
lacks a sunroof, aircon or Bluetooth, but also has no Qi-compatible
charging mat, forcing me to fall back on a USB adapter plugged
into the cigarette lighter.
Nik Rawlinsonflow of electricity through a circuit to
that of water through plumbing. Amps is
the speed of the water current, and volts
is a measure of the system’s capacity to
move water from one place to another.
Swap centimetres for volts, for example,
and you might describe a pipe with a
1cm diameter as being a 1-volt pipe,
and an equivalent pipe with a 2cm
diameter as being a 2-volt pipe, and so
on. Multiplying amps by volts gives you
a figure for watts. So, increasing the
figure for either (or both) will increase
the number of watts (or power) running
through the overall system.
If we continue with our plumbing
analogy, increasing the water pressure
(amps) but maintaining the size of
the pipe (volts) would increase the
watts. So would enlarging the pipe but
maintaining pressure – or increasing
both simultaneously. The result would be
the same: the water would move from the
tank to where it is needed more quickly
(the figure for watts would be higher).
Likewise, a higher watt rating (wattage)
indicates a receiver that can deliver more
power from the Qi base station to your
phone in a given time frame.
Your charging speed will also be
affected by the charger itself (the base
station on which you rest the receiver
connected to your phone), and the rate
at which your phone will accept an
incoming charge. Receivers, after all,
aren’t batteries in their own right, and
can’t power your phone.
Base stations also have a watt rating,
which may exceed the capacity at which
your chosen receiver can pass energy
to your phone. This isn’t necessarily a
problem, though, as it gives you capacity
that might be useful in the future.
Apple’s 15W MagSafe wireless charger,for example, steps down to 12W when
charging the iPhone 12 mini and iPhone
13 mini.
We conducted our tests using the 5W
pad of an Anker PowerWave dual base
station kit as our charger (£29.99 from
http://www.snipca.com/41795, pictured left),
the other half of which supports 10W
charging. We charged both an iPhone
6 and a Motorola Moto G7 (running
Android), each of which was flat and
unable to turn on at the start of our tests.
Both phones came to life within 10
minutes of first being placed on the
charging pad, allowing us to switch them
on so they could receive messages. The
iPhone’s 1810 mAh battery reached athe socket. The Motorola phone pictured
above is a ‘narrow side up’ device: the
upper edge of the socket is pinched in at
either side, and thus narrower than the
lower edge.2
Work out the
charging speed
When choosing a receiver,
comparing their stated output can help
you work out how quickly they’ll charge
your device. This won’t be an issue if
you’re going to dock your phone on a
bedside charger every night and give
it a solid eight hours, but if you’ll be
dropping it on to a charging pad in your
car (a growing number of new cars now
come with integrated Qi-charging mats)
it could affect how much you can top up
on short journeys.
The two receivers we bought each
send five watts of energy to the phone at
one amp. Amps measure the flow rate- effectively the speed – of the energy
leaving the receiver. The higher this
number, the faster the energy is flowing.
Multiplying the amp measurement by the
number of volts gives the figure for watts
(five, in this instance).
If you’re confused, you’re not alone,
which is why it’s common to liken the
This Motorola phone has a narrow side up
microUSB socket