iOS includes several useful tools for displaying how much battery life your iPhone has left, as well as which apps are consuming the most of your battery. However, none of these tools actually tell you anything about your battery’s long-term health, which is just as important.
Battery Health vs. Battery Life
Battery health is different than battery life. Battery life determines how long your battery lasts on a single charge, but your battery health determines how much your battery life diminishes over time. After a year, your battery life won’t be as long as when the phone was new, and it will continue to degrade as the years go by.
If you’ve ever had to constantly recharge your older phone because the battery would only last a couple of hours, then you know how annoying this is. Compounding the problem is that most mobile phones don’t have a user-accessible battery that can be swapped out with a new, fresh battery.
Fortunately, there are two excellent metrics you can check to get a big picture view of your battery’s health. The first is the maximum remaining capacity (the total charge your battery can hold). The second is the total number of charge cycles the battery has gone through.
Real world use always chips away at the total capacity over time, but a healthy battery will have only a few percents shaved off its original capacity. Furthermore, lithium-ion batteries (those found in pretty much every smartphone) degrade a tiny bit with each charge cycle. Apple says they design their iPhone batteries so that the battery should retain roughly 80% of its capacity after 500 charges.
Battery health data is not available in the iOS settings, so you have to take some extra measures to get this information, and there are several ways to do it.