Comment by LinaLauneBaer | Hacker News Reader

Comment by LinaLauneBaer | Hacker News Reader

I always wonder if slowing down the phone is a good solution. By slowing down the CPU the CPU needs less energy. But at the same time the user has to wait much longer in order to finish what he was trying to do. Thus the screen is on for a longer period of time. Isn't the screen one of the main energy consumers in an iPhone?

Launching apps on my iPhone 6 (which needs a new battery) takes for ages (even when compared to my older but less used iPhone 5S). I can't imagine that the extended "screen lit"-time does not have a big impact as well.

Also: I am one of the few users who would be totally fine with the iPhone shutting down at 20% or so (if I have the full performance as I used to) because my iPhone is rarely going near 20%. At work I can charge. At home I can charge. When I am on the go I usually am not using the phone that much... However playing hearthstone when I am in bed, loading the phone, everything takes much longer as well which makes playing games less fun...

The issue is not specifically about battery life, but about the ability of the battery to provide a stable voltage under load. The voltage of the cells sags more under high current draw as the battery ages; reducing the current draw by throttling the maximum SoC frequency seems to be intended to avoid the problem where the voltage dips to a level that causes the SoC to shut down suddenly.

Edit: I see others have addressed this in the very long time it took me to express myself!

As I understand it, as batteries degrade it's not only the total capacity that drops, but also the voltage the battery can deliver and the CPU requires a certain voltage to run at a higher frequency.

So, a fully charged, yet degraded battery, may have the overall energy needed to run a CPU at normal Mhz, but may not be able to deliver that energy fast enough.

As I understand it, the main issue is that the power output of the batter decreases as it degrades, not just its total capacity. Apple claims that the throttling is needed in order to prevent the processor from automatically shutting off because it can't draw as much power as it requires -- not just to prevent the battery from draining faster.

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