We all know the frustration: you take your iPhone off the charger at 100% in the morning, and by lunchtime, you're already hunting for a power bank. While software glitches can sometimes cause rapid drain, the most common culprit is physical degradation of the lithium-ion battery.
Fortunately, iOS provides built-in tools to monitor this degradation. Here is how to check your battery health and interpret what the numbers actually mean.
Checking the Health
- Open the Settings app on your iPhone.
- Scroll down and tap on Battery.
- Tap on Battery Health & Charging (or just Battery Health on older iOS versions).
Decoding the Metrics
On this screen, you’ll see two critical pieces of information:
#### 1. Maximum Capacity
This is the big number everyone looks at. When your phone is brand new, this should read 100%. As you use the phone and go through charge cycles, the chemical age of the battery increases, and its ability to hold a charge diminishes.
- 100% - 90%: Your battery is in excellent health. You should be experiencing normal battery life.
- 89% - 81%: Normal wear and tear. You might notice slightly shorter battery life, but the phone should still comfortably get you through most of the day.
- 80% and Below: This is the critical threshold. Apple considers a battery depleted once it hits 80%. You will likely experience noticeable battery drain, and you may see a message saying "Your battery's health is significantly degraded."
#### 2. Peak Performance Capability
Lithium-ion batteries don't just lose capacity as they age; their ability to deliver rapid spikes of power (impedance) also decreases. When a degraded battery is asked to do something demanding (like launching a complex game or taking burst photos), it might not be able to deliver the required voltage, causing the phone to unexpectedly shut down.
If this happens, iOS enables "Performance Management." It intentionally slows down your processor to prevent further unexpected shutdowns. If your Peak Performance Capability says anything other than "Your battery is currently supporting normal peak performance," your phone is actively throttling its own speed to stay alive.
iOS 17 and iPhone 15+ Changes
If you own an iPhone 15 or newer running iOS 17+, Apple provides even more detail. In the Battery menu, you can now see the exact Cycle Count (how many times you've fully drained and recharged the battery), the Manufacture Date, and the First Use Date. Apple states that iPhone 15 batteries are designed to retain 80% capacity at 1000 complete charge cycles, double the 500 cycles of previous generations.
When to Replace
As a rule of thumb, if your Maximum Capacity is below 80%, or if your phone is experiencing unexpected shutdowns and performance throttling, it is time for a new battery.
Replacing the battery doesn't just improve runtime; it restores the full speed and processing power of the phone. If you are constantly tethered to a charger, bring your device to Tech Service Centre in Hounslow. We can perform a professional battery replacement, often in under an hour, giving your iPhone a new lease on life.