Your phone dies by lunchtime, even though it was fully charged in the morning. Or it shuts down during a call while still at 30%. Or it gets hot for no apparent reason. Most people in this situation look for a new cable, change the charger, or restart their phone. But the problem is usually something else entirely.

What the problem really is

A lithium-ion battery degrades with every charge cycle—it's physics, not a defect. After 400–500 full cycles, an iPhone battery loses a noticeable amount of capacity and starts behaving strangely. Not because the phone is broken, but because the actual capacity is no longer what it was initially.

The problem is that the symptoms of a worn-out battery and a "just needs a charge" situation look the same at first glance. The phone shuts down, lags, or gets hot. That is why many people go months with a sick battery, thinking that's just how it's supposed to be.

Five signs that your battery can no longer keep up

  • The phone turns off at 15–40% charge, and after a restart, it shows those same percentages again. The battery controller can no longer accurately measure the remaining charge—this is called a calibration failure.
  • Under load—navigation, video, or a call—the percentage drops sharply and non-linearly. It was 60%, and five minutes later it's 35%.
  • The phone gets noticeably hot even when idle or during light tasks.
  • In Settings → Battery → Battery Health, the number is below 80%. Apple itself recommends this threshold for replacement.
  • Performance management mode has kicked in. This means iOS is limiting the processor speed so the phone doesn't shut down during peak loads—because the battery can no longer handle it.

What you can check yourself

The first step is to check Settings → Battery → Battery Health & Charging. A number below 80% speaks for itself. You can also see if performance management is enabled there.

You can try to calibrate the battery: drain the phone completely until it turns off, then charge it to 100% without interruption, preferably using an original adapter. Sometimes this evens out the controller's readings. But if the battery is truly worn out, it won't help; it will only confirm it.

It is also worth checking which apps are consuming the most power—in the same Settings → Battery menu. Sometimes a messenger app runs in the background and drains the whole phone in half a day. That is not a battery issue; it is a software problem.

Two cases from our practice

We recently had an iPhone 13 brought in—the owner complained that the phone wouldn't last more than half a day. We checked the battery health: 71%. The phone is less than three years old, but the battery is already at the level of a five-year-old one. It turned out she was constantly charging it at night with a powerful 65-watt adapter—this significantly accelerates degradation. We replaced the battery, and the phone is back to lasting two days.

Another case was an iPhone 11 that would shut down at 20% while outside in the winter, but would turn back on once it warmed up. This is a classic for old batteries: at low temperatures, the internal resistance of the battery increases, and the phone simply doesn't get the current it needs. Such an iPhone is a brick outside in the winter and a normal phone at home.

When it is definitely time to see a technician

If the capacity is below 80%, the phone shuts down with a non-zero charge, or performance management mode has been enabled, a new charger won't solve the problem. Neither will a new cable. Battery replacement at our service center takes about an hour and costs from 2 500 rubles, depending on the iPhone model.

If you are not sure, come to iClub for a diagnostic—it's free. We will check the battery health and give you honest advice: whether it's worth replacing it right now or if it's still too early. We are located at 35 Kommunisticheskaya St., Novosibirsk.