If your iPhone battery doesn’t seem to last as long as it used to, Apple has a few tools that can help. Recent models include smarter charging controls to slow battery wear and new ways to check your battery’s overall health – including how many full charge cycles it has been through. Here’s how those features work today, and how to tell when it’s time for a replacement.
Why lithium-ion?
iPhones rely on lithium-ion batteries because they’re light, efficient, and support fast charging. They power up quickly to around 80% for convenience, then slow down for a gentler top-up that helps protect long-term health. You don’t need to drain them before recharging; lifespan is instead tied to charge cycles – the number of times you’ve used the equivalent of a full 100% charge, even if that’s spread across multiple days.
As these batteries chemically age, their maximum capacity gradually decreases, reducing battery life and peak performance. Good charging habits help slow this down, but some wear is inevitable.
Optimization and limits
On iPhone 15 and later, Apple has expanded its charging controls. You can now set a specific charge limit between 80% and 100%. Your iPhone will charge to just under that level and then stop, only topping up again if the battery drops more than a few percentage points while plugged in.
If you choose a 100% limit, Optimized Battery Charging becomes available. This feature learns your routine and delays charging past 80% when it expects you to remain plugged in for several hours – typically overnight – so your battery spends less time sitting at full charge. When it activates, you’ll see a Lock Screen notification showing when your phone is scheduled to finish charging. If you need it fully charged sooner, press and hold the notification and tap Charge Now.
To adjust these settings, go to Settings > Battery > Charging on iPhone 15 and later, or Settings > Battery > Battery Health & Charging on iPhone 14 and earlier.
Your iPhone may occasionally recommend a lower limit based on your habits – for example, suggesting 95% to help preserve battery lifespan. And even with a lower limit set, it may occasionally charge to 100% to keep its state-of-charge estimates accurate.
Check your cycle count
iOS also shows your battery’s cycle count – the most useful indicator of long-term wear. A cycle represents 100% of battery capacity used, not necessarily in one go. You’ll find this in Settings > General > About, listed alongside the battery’s manufacture date.
When to replace your battery
All lithium-ion batteries degrade over time. As capacity drops, your iPhone won’t last as long between charges and may lower performance to prevent unexpected shutdowns.
You can check your current maximum capacity under Settings > Battery > Battery Health & Charging. If it falls below about 80%, it’s usually time to consider a replacement. Apple or an authorised repair provider can install a new battery for far less than upgrading your entire device – often restoring your iPhone’s stamina surprisingly well.