Lithium-ion batteries, like the ones used in modern iPhones, chemically age over time. This aging process is accelerated when the battery is frequently kept at a 100% state of charge for prolonged periods, such as when you leave it plugged in overnight. To combat this and extend the overall lifespan of the battery, Apple introduced a feature on the iPhone 15 and later models that allows you to artificially cap the maximum charge level at exactly 80%. By preventing the battery from ever reaching full capacity, you significantly reduce the stress on the battery’s internal chemistry.
How the 80% Limit Differs from Optimised Battery Charging
You may already be familiar with “Optimised Battery Charging,” a feature that has existed on iPhones for several years. Optimised Charging uses machine learning to learn your daily routine; it stops charging at 80% overnight but finishes the final 20% just before it predicts you will wake up. The 80% Limit is different. It is a hard, absolute cap. If you enable this feature, your iPhone will never charge past 80%, regardless of how long it remains plugged into the charger. Apple notes that the iPhone will occasionally charge to 100% to recalibrate the battery state-of-charge estimates, but it will immediately resume the 80% limit thereafter.
Enabling the 80% Charging Limit
This setting is exclusively available on the iPhone 15, iPhone 15 Pro, and newer models running iOS 17 or later. If you have an iPhone 14 or older, you will only see the standard Optimised Battery Charging option.
- Open the Settings app on your iPhone.
- Scroll down and tap on Battery.
- Tap on Battery Health & Charging.
- Tap on Charging Optimisation.
- You will be presented with three options: Optimised Battery Charging, 80% Limit, and None.
- Tap 80% Limit to select it. A blue checkmark will appear next to it.
When Should You Use the 80% Limit?
Choosing to artificially reduce your phone’s battery life by 20% every day is a trade-off. This feature is highly recommended if you are a “desk worker” who constantly rests their phone on a MagSafe charging stand throughout the workday, or if you use CarPlay on a long daily commute where the phone is constantly plugged in. In these scenarios, the phone is tethered to power so frequently that you rarely need the full 100% capacity anyway, making it the perfect situation to prioritise long-term battery health.
When Should You Disable the 80% Limit?
If you are travelling, attending an all-day conference, or know you will be away from a charger for an extended period, you should temporarily disable the limit. Simply navigate back to Settings > Battery > Battery Health & Charging > Charging Optimisation and select None. This will allow the phone to charge to 100%, giving you the maximum possible runtime for that specific day. You can re-enable the 80% limit when you return to your normal routine.