There's a number buried in your iPhone settings that a lot of people treat as gospel. Settings > Battery > Battery Health. Once it dips below 80%, Apple considers the battery degraded and might even show a service recommendation. But that percentage alone isn't the full story.
Here's what's actually worth paying attention to.
What the percentage actually measures
Battery health in iOS measures your battery's maximum capacity relative to when it was new. A battery at 79% can technically hold 79% of its original charge. That sounds simple, but the number doesn't account for how you use your phone or what that capacity means in practice.
A heavy user who needs their phone all day will notice the difference sooner than someone who tops up regularly during the day. The percentage is a starting point, not a verdict.
Signs that matter more than the percentage
The phone shuts down with charge remaining. This is the clearest sign of a failing battery. If your iPhone turns off at 15% or 20%, the battery can no longer reliably deliver power under load — even though the software still shows capacity left.
The battery percentage jumps erratically. Going from 40% to 20% in five minutes, or jumping back up when you restart — this is the battery misreporting its own charge. It's caused by a degraded cell that can't give an accurate reading.
The phone gets unusually hot while charging or during normal use. Some warmth while charging fast is normal. But if the back of the phone gets noticeably hot during everyday tasks, the battery is working harder than it should to deliver the same output.
Performance management has kicked in. Apple introduced performance throttling to prevent unexpected shutdowns caused by degraded batteries. If your iPhone is noticeably slower than it used to be, performance management may be limiting processor speed to compensate for the battery.
When replacement actually makes sense
If you're seeing any two of the symptoms above, replacing the battery is almost always the right call. At $69–$199 depending on the model, it's a fraction of the cost of a new phone and will typically restore the experience you had when the phone was new.
If you're below 80% but the phone still gets you through the day without issues, there's no urgency. Monitor it over the next month or two.
If you're above 80% but the phone is behaving badly — shutting down unexpectedly, running hot, jumping percentages — the percentage is misleading. The battery still needs replacing.
A note on third-party battery warnings
On iPhone 12 and later, a third-party battery replacement will show a message in Settings saying the battery health cannot be determined. This is a software restriction, not a sign that something is wrong with the repair. The battery still works normally. Some premium-grade batteries can suppress this message — ask us when you come in if that matters to you.
What to do next
If you're in Canberra and think your iPhone battery needs attention, bring it in to The Fone Club at Majura Park Shopping Centre, Canberra Airport. We'll check the battery during diagnosis before recommending a replacement. No fix, no fee.