SEPTEMBER 2020 MACWORLD 87If you ever wondered why
your devices charge very fast
and then very slowly, that’s why.
And 100 percent isn’t really “100
percent.” It’s the maximum that a
battery’s controlling circuitry or
connected operating system
believes it can safely hold when
“full.” Even with the most careful
algorithms to get to 100 percent,
lithium-ion batteries simply age
faster when they’re topped up
all the time. Battery University
explains it succinctly (go.
macworld.com/btun):
Lithium-ion suffers from stress
when exposed to heat, so
does keeping a cell at a high
charge voltage...Exposing the
battery to high temperature
and dwelling in a full state-of-charge for
an extended time can be more stressful
than cycling.Apple recognized this as a problem
with iPhones in particular, and built into
iOS an awareness of a battery’s available
capacity, which led it to throttle certain
tasks when the battery couldn’t deliver
enough juice without the iPhone shutting
down. (See Settings → Battery.) Much has
been written about Apple’s lack of
disclosure, apology for the issue (go.
macworld.com/apap), and discounted
battery-replacement program for older
phones.
This minor crisis also led the company
to add more detail about battery capacity
and charge, and shape charging more
intelligently. Apple no longer always
ensures an iPhone and iPad charges to
100 percent when plugged in, but
observes your charging patterns and
adapts to charge only as necessary to give
you the most stored juice you need at any
given time.iOS manages battery charging by adapting it to your
usage pattern and charging to full in anticipation of when
you need it daily.