If you suspect that your iPhone is running more slowly than it used to do, here’s how to find out, and if so, disable the CPU “throttling”.
Every time you recharge your iPhone, its battery is degraded by a tiny amount. This is an inherent limitation which all lithium batteries suffer from, and it means that over several months and years, the total capacity of your iPhone’s battery drains, leaving you with fewer hours in the day to enjoy your iPhone.
If you’re iPhone is more than a year old, then chances are it’s running more slowly than it used to do. This isn’t a conspiracy to convince you to buy the latest iPhone, but instead, an attempt to prevent your iPhone from switching off suddenly when the processor suddenly tries to suck more power from the battery. By throttling the CPU, less battery juice is needed at once.
With iOS 11.3, Apple has added the ability to check on your battery to see if it has degraded to the point where the CPU is throttled; and if so, give you the ability to disable this mode to keep your iPhone running as fast as it was the day you bought it.
First, make sure you have an iPhone that is affected by CPU throttling. These are the models affected:
- iPhone SE
- iPhone 6,
- iPhone 6 Plus
- iPhone 6S
- iPhone 6S Plus
- iPhone 7
- iPhone 7 Plus
If you own one of the iPhone’s above, open the Settings app, tap on the Battery option, then choose Battery Health (Beta). On the following panel, you’ll see the maximum capacity of your iPhone’s battery. If it’s less than 80%, or if your iPhone has suffered from an expected shutdown, then the page will say “…performance management has been applied to prevent this from happening again”. You will also see an option to turn CPU throttling off.
If you turn CPU throttling off, and then experience another unexpected shutdown, CPU throttling will be turned back on automatically; which means you’ll need to go back to Settings > Battery > Battery Health (Beta) to turn it off again.
If you have experienced this problem, then it’s a good idea to take your iPhone to the nearest Apple Store and get the battery swapped for a new one. This costs $29.