iPhone 6An iPhone 6, which Apple released in 2014.Flickr/Yanki01
  • Replacing an older iPhone's battery can help it perform better on speed tests.
  • That's because Apple is using a new power-management feature to prevent iPhones with older batteries from suddenly shutting off, the company told Business Insider on Wednesday.
  • Apple says it isn't purposely slowing down older iPhones to encourage customers to buy new models, debunking a popular conspiracy theory.

Over the past few months, people have discovered that older iPhones curiously become fasterafter the battery is replaced.
That, of course, has fueled conspiracy theories that Apple slows down older iPhones when a new model comes out. Data from a top iPhone benchmark developer published earlier this week seemed to confirm it.
But Apple explained on Wednesday why iPhones with older batteries might have lower peak processor performance.
It turns out that Apple is limiting how much power an iPhone processor can draw in certain circumstances, therefore limiting the processor's peak performance.
But it's not to make older iPhones slower — it's a new feature to help prevent them from suddenly turning off.
Here's Apple's full explanation, provided to Business Insider by a representative:
"Our goal is to deliver the best experience for customers, which includes overall performance and prolonging the life of their devices. Lithium-ion batteries become less capable of supplying peak current demands when in cold conditions, have a low battery charge or as they age over time, which can result in the device unexpectedly shutting down to protect its electronic components.
"Last year we released a feature for iPhone 6, iPhone 6S and iPhone SE to smooth out the instantaneous peaks only when needed to prevent the device from unexpectedly shutting down during these conditions. We've now extended that feature to iPhone 7 with iOS 11.2, and plan to add support for other products in the future."
Apple's point is that if an iPhone tries to draw more power than the battery is capable of, it will suddenly shut down, as many did before last year's update. So what it's doing instead is controlling how much power older phones can draw so it can prevent the device from failing. Older batteries simply can't provide as much power as new ones.
Apparently, the company is happy with its current fix and plans to roll it out to other products.
Rechargeable batteries have a limited lifespan — and most Apple products have a built-in one — so the shutdown issue is something all devices will eventually have to deal with if they're used long enough.
Apple expects an iPhone to get three years of use, so if you charge your iPhone every night, you might want to get a new battery before its third year of service.
Apple also says iPhones work best at room temperature, or between 32 and 95 degrees Fahrenheit.
So if you think your phone isn't performing at its best, or you want to refresh an old phone, try replacing its battery. Not only is it likely to help your phone last an entire day — it might give it a speed boost too.

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