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Comment by j_coder | Hacker News Reader

It is about battery life. This is how the battery should be measured: 100% -> Doesn't charge more 0% -> Do no provide enough voltage/current for safe operation at current power mode.

At 5% the phone could switch (configurable) to extended battery mode (low power mode) and alert the user.

As the battery ages the user will notice better a faster battery discharge (from 100% to 0%) and not the performance slowdown.

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Your demonstrating the same ignorance the post you’re replying to is complaining about. It is not physically possible for the phone to draw sufficient power off a degraded battery to power it in high performance modes. The battery just doesn’t provide enough electrical current. Apple isn’t stepping back performance on degraded batteries to keep battery life. They are doing it to keep peak current draws at a level the battery can support so that the phone doesn’t hard shutoff when it is receiving insufficient power.

I think you don’t read the comment. If the battery do not have enough power the level would be 0%. The time from 100%(plugged in) to 0% will depend on how degraded is the battery. It is not difficult to understand. You are repeating Apple excuses. Mobile phones had been dealing with degrading batteries for a long time.

That’s not how batteries work. Degration over time causes a battery to not just store less total capacity on a “full” charge, but also to output less current at the required voltage. The latter is what is preventing the phone from operating under a full load at peak performance without a hard shut off.

The issue is the device shutting off while there is still charge on the battery, not the battery reaching 0% faster.

To be clear: 0% would be when current voltage or current mAh level is bellow what the phone needs to operate at maximum capacity.

“Voltage and mAh are two different, but interrelated, things. voltage is a measure of the electrical power a battery can deliver, while mAH (milli-Amp hours) is a measure of how long the battery will maintain usable voltage at a given output current.” https://www.quora.com/How-much-mAh-will-equal-to-1-v

It is the opposite. Batteries degradation acts as an internal resistance at rest (Rd) that increases over time. There is a second resistance (Rc) that increases as you discharge the battery. As you draw current (I) from the battery the nominal voltage decreases according to Omhs law V = Vn - I*(Rd + Rc).

You can plot different voltage charts as the battery discharges at different stages of degradation (increased Rb). As you know the peak current that phone drains at maximum load you know the minimum voltage it requires to operate. At this minimum voltage you show 0% (or a little higher so the phone can have enough power to gracefully shutdown).

What Apple is doing is slowing down the processor so it drains a smaller current reducing the minimum voltage the phone needs to operate extending the battery life (that also measures the time between 100% to 0%). This way you don't complain that an one year old phone battery is discharging too fast probably because of battery fault or wrong specification. There also a good side effect for Apple of decreased performance perception that induces to premature phone upgrades.

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