Has your iPhone ever dropped to one percent and then stayed there without turning off for a suspiciously long time? There has been questions about how most iPhones manage to stay alive with 1% battery for considerably long time, it has been experienced by a lot of users, who, some find it weird, and others find it questionable ‘why Apple didn’t just show higher percentage of battery?’ Let’s talk bout this!
There’s a reason for this. And it isn’t limited to iPhones. Virtually, any rechargeable device can experience this behavior, which results from battery capacity being really difficult to measure, batteries aren’t like gas tanks where the energy remaining can be physically measured by volume, instead voltage output or electrical pressure is used as the main metric for calculating capacity, when the pressure output is strong the battery is mostly full as it weakens the battery capacity drops, the challenge is interpreting the voltage level as a percentage of remaining battery, since there are other variables that influence the number, for example if you’re using an iPhone in freezing temperatures a portion of its battery won’t be available until it becomes warmer, also if you had your iPhone for many years its battery could be in poor condition, since lithium-ion cells chemically aged over time.
You may find this forum post about converting battery remaining into percentage on general devices interesting on Quora,
This decline in performance causes issues like shorter battery life, slower app launching, lower frame rates, lower speaker volume, and inaccurate battery percentages. If you’ve ever had an iPhone drop from 90 to 10% in less than an hour, that’s the reason. So even though companies like Apple create complex algorithms to calculate remaining battery they aren’t perfect, in fact they tend to underestimate how much battery is left just in case, that’s why it might seem like your iPhone drops faster from 100 to 90% then 30 to 20%, even though the battery is decreasing by 10% in both scenarios, the algorithm is discovering more energy near the end of the discharge cycle due to underestimating the capacity, and in some circumstances your iPhone will reach 1% with quite a bit more in the tank resulting in that last percentage delivering unusually long usage before the device shuts down.
This article is inspired by a video in Apple Explained YouTube channel.