Where to find your battery health on iPhone
Your iPhone tracks its own battery condition and shows you the data in Settings. Open Settings, tap Battery, then Battery Health & Charging. You will see a percentage labeled Maximum Capacity — this is the number that matters.
Maximum Capacity tells you how much charge your battery can hold right now compared to when it was brand new. A new iPhone shows 100%. A battery at 80% can hold four-fifths of the original charge. That same battery will drain faster than it did on day one, even if you charge it fully.
The same screen also shows Charging Optimization status. If it says "Optimized Battery Charging" is on, your phone is slowing down charging past 80% to extend the battery's lifespan. This is normal and intentional — you can turn it off if you need full charge quickly, but leaving it on is gentler on the battery.
Key Takeaways
- Maximum Capacity percentage in Settings > Battery > Battery Health & Charging shows how much charge your battery can hold compared to when it was new.
- A battery at 80% capacity still works, but drains faster and may not last a full day of heavy use.
- Below 80% capacity, your iPhone may show a "Low Power Mode" suggestion and performance may slow down on older models.
- Optimized Battery Charging slows charging after 80% to preserve battery lifespan and is safe to leave on.
- Battery capacity naturally declines over time; replacing the battery costs less than replacing the phone.
What the percentage actually means
Maximum Capacity is not a health score out of 100. It is a measurement of charge storage. Think of it like a gas tank: a new tank holds a full gallon, a worn tank holds 0.8 gallons. Both tanks work. The smaller one just empties faster.
At 100% capacity, a full charge might last 15 hours of normal use. At 80% capacity, that same full charge lasts about 12 hours. At 60% capacity, you might get 9 hours. The math is roughly linear — lower capacity means shorter battery life per charge.
Apple considers 80% capacity the threshold where a battery is still "normal." Below 80%, the battery is aging faster than expected, but it is not broken. Many people use iPhones at 70% or 60% capacity for months or years without problems.
When battery capacity drops and why
All rechargeable batteries lose capacity over time. Lithium batteries — the kind in iPhones — degrade a little with every charge cycle. A charge cycle means using 100% of the battery's power, whether that happens in one day or spread across several days.
Temperature matters more than you might think. Batteries degrade faster when they are hot. Leaving your iPhone in a hot car, using it while charging, or running heavy apps in warm weather all speed up capacity loss. Cold temperatures slow degradation but do not cause permanent damage.
How you charge also affects lifespan. Charging to 100% and staying at 100% for hours stresses the battery more than charging to 80% and stopping. This is why Optimized Battery Charging exists — it learns your charging habits and holds the charge at 80% until you are about to use the phone, then finishes charging.
The difference between capacity and performance
Maximum Capacity and Performance Capacity are two separate things, and Apple shows them separately. Maximum Capacity is how much charge the battery holds. Performance Capacity is whether the phone slows itself down to protect the battery.
If Performance Capacity drops below 80%, your iPhone may throttle — run slower — to avoid sudden shutdowns. This is a protection feature. An old battery cannot deliver power as quickly as a new one, so the phone reduces demand to match what the battery can safely provide.
You will see a message in Battery Health & Charging if Performance Capacity has dropped. It might say "Peak Performance Capability: Reduced" or offer to replace the battery. This does not mean the phone is broken, but it does mean the battery is aging significantly.
How to slow down battery degradation
Keep your iPhone cool. Avoid leaving it in direct sunlight, in a car on a hot day, or in a case that traps heat while charging. If your phone feels warm to the touch during normal use, remove the case or move it to a cooler place.
Turn on Optimized Battery Charging in Settings > Battery > Battery Health & Charging. This feature learns when you usually charge your phone and holds the charge at 80% until shortly before you wake up or typically unplug it. It is safe and extends battery lifespan by months or years.
Avoid letting the battery drain completely to 0% regularly. Charging from 20% to 80% is gentler on the battery than charging from 0% to 100%. If you use Low Power Mode when the battery is above 20%, you reduce the number of full charge cycles the battery goes through.
Do not leave your iPhone plugged in overnight at 100% charge for weeks on end. If you must charge overnight, Optimized Battery Charging will help, but unplugging once the phone reaches 100% is better for long-term battery health.
When to replace your battery
You do not have to replace the battery at any particular capacity percentage. Some people replace at 80%, others at 60%, others not at all. It depends on how much battery life you need and how often you charge.
If your phone shuts down unexpectedly even when the battery percentage shows 20% or higher, the battery is failing and should be replaced. If you are charging multiple times a day and it is frustrating, replacement might be worth the cost. If you charge once a day and that works for you, there is no rush.
Battery replacement costs vary. Apple charges around $69 to $99 depending on the model, and the process takes a few hours to a few days. Third-party repair shops often charge less but may use non-Apple batteries. If your iPhone is under warranty or you have AppleCare+, battery replacement at reduced cost may be available.
What you cannot see in Battery Health
The Battery Health screen does not show you cycle count — the number of times the battery has been charged. It does not tell you the exact age of the battery or predict when it will fail. It shows only current capacity and whether performance has been reduced.
If you want detailed battery information including cycle count, you can check it on a Mac. Connect your iPhone, hold Option, and click the battery icon in the menu bar. On Windows, third-party apps like CoconutBattery show more detail, though they are not official Apple tools.
Battery Health does not account for software issues that drain the battery faster. If your battery percentage drops unusually quickly, check Settings > Battery to see which apps are using the most power. A misbehaving app can make a healthy battery seem weak.
Frequently Asked Questions
Is 85% battery capacity bad?
No. Apple considers batteries normal up to 80%, so 85% is still in the healthy range. You will not notice much difference in daily use. Most people do not replace the battery until it drops to 70% or lower, depending on their charging habits.
Why does my battery capacity drop so fast?
Heat is the most common cause. Check if you are charging in a hot environment, using the phone while it charges, or keeping it in a thick case. Software bugs can also drain the battery faster than normal — restart the phone and check which apps are using the most power in Settings > Battery.
Can I replace the battery myself?
iPhones are difficult to open safely without damaging the screen or other components. Apple and authorized repair shops have the tools and training to do it without breaking something else. Self-repair kits exist but carry a high risk of damage that costs more to fix than a professional replacement.
Does Optimized Battery Charging actually work?
Yes. Studies and real-world use show that keeping the charge at 80% for most of the day extends battery lifespan by several months to over a year compared to charging to 100% every night. The trade-off is that you might not have a full charge first thing in the morning if you charge overnight.
What if my battery health is below 50%?
The battery still works, but you will notice shorter battery life and may need to charge twice a day. If the phone shuts down unexpectedly or the battery drains visibly while you watch, replacement is worth considering. At this point, the battery is old enough that replacement is usually cheaper than buying a new phone.