News for hackers. Stuff that matters.

A comment on IPhones start slowing down after a year. Parent comment

Re:IPhones start slowing down after a year by cptskippy on Thursday December 21, 2017 @12:13PM (#15980641)
Batteries have a predictable discharge cycle. They're fully charged when their output voltage stops increasing and as they discharge the output voltage slowly falls until it reaches a certain threshold where the output voltage is no longer enough to power the device. That cut off voltage is a fixed number. The part that varies is the time it takes to go from fully charged to the cut off voltage.

As a battery degrades, the time is reduced.

Regardless of what the initial voltage is, a plot can be drawn based on measurements of the voltage to see how quickly it's approaching the cut off voltage.

So the battery capacity should really be where the voltage is relative to the last peak when fully charged compared to the cut off voltage.

If Apple is reporting a battery at 40% capacity when it cuts off then they're fudging their numbers.

[ Parent | on HN ]
Re:IPhones start slowing down after a year by hinkley on Thursday December 21, 2017 @12:54PM (#15981054)
Now, I know that different battery chemistries have different discharge profiles and this waters down my point a bit, but hear me out.

I started buying LED flashlights when the first couple of designs with high efficiency voltage regulator circuits showed up. The one my buddy had was only fit for a reading light for the last couple of hours of use.

People used to understand that things got dimmer or slower when the battery was almost dead. Due to circuitry these flashlights kept going even though the battery voltage had dropped below the shutoff voltage for an LED. Shouldn’t we maybe have built on that familiarity? Couldn’t we still?

[ Parent | on HN ]
Re:IPhones start slowing down after a year by TeMPOraL on Thursday December 21, 2017 @12:46PM (#15980950)
Drawing power causes voltage drops; I suspect what they're saying is that a degraded battery under heavy load will momentarily drop from 40% to under cutoff threshold.
[ Parent | on HN ]
Re:IPhones start slowing down after a year by cptskippy on Thursday December 21, 2017 @02:14PM (#15981880)
Large voltage drops under load are typically an indication of a bad cell or battery. You could argue this is beneficial to the customer but Apple is hiding the fact that they're doing this. Why?

I recall when they switched to non-replaceable batteries in MacBooks, they boasted how their battery lives were the best and would last x years. Is this how they did it?

[ Parent | on HN ]