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Everything to Know About Apple Slowing iPhones Because of Old Batteries

Apple CEO Tim Cook discusses the iPhone during an Apple media event in San Francisco on Sept. 7. © Beck Diefenbach / Reuters REUTERS

Apple recently acknowledged that it slows the performance of some iPhones because their older batteries are unable to properly power devices raises a lot of questions for iPhone owners. Should they pay to get their batteries replaced? If so, what’s the best way to do it?

Whatever the case, many iPhone owners are upset. Several have filed lawsuits alleging that Apple aapl swindled them by failing to disclose that it would slow phones—all in a sneaky attempt to get them to buy newer iPhones.

Apple has apologized for how it’s communicated to the public about Batterygate, and denied that it would “do anything to intentionally shorten the life of any Apple product, or degrade the user experience to drive customer upgrades.”

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In an effort to make nice with customers, the company also reduced the price of replacing out-of-warranty iPhone batteries to $29 from $79.

The entire topic is confusing for many iPhone owners. Here’s our guide to what you need to know.

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Why does Apple slow down iPhone performance?

It’s all about the batteries. Apple said that the lithium-ion batteries that power the iPhones weaken over time, causing smartphones to suddenly turn off despite showing that their batteries still have some charge left in them. For example, an iPhone battery with a 20% charge remaining may be unable to power the device (especially if it has multiple apps running simultaneously). Instead, it may shut down.

As Fortune’s Jeff Roberts personally experienced in Dec. 2016, having an iPhone abruptly shut down can be a major pain, especially when using mobile mapping apps to navigate in unfamiliar city streets. For the record: Cold weather also temporarily weakens iPhone batteries.

To deal with the problem, Apple released last year an update to its iOS software to fix the problem of iPhones unexpectedly turning off. The update slowed the overall performance of iPhone so as not to overload its battery. In other words, you end up trading performance for reliability.

What happens when your iPhone’s performance is throttled?

When Apple’s software intervenes to preserve your iPhone battery, apps running on the device may take longer to open and run more slowly (scrolling web pages may take more time, for example). Your iPhone may also automatically dim itself and lower its speaker volume. However, Apple said that its recent battery updates shouldn’t hurt the performance of some key iPhone features like the ability to make cellular calls, use GPS, or buy things using Apple Pay.

What iPhone models are impacted?

Apple has said that the battery software update it released a year ago affects the iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, and iPhone SE. Apple also said that it applied that battery tweak to the iPhone 7 and the iPhone 7 Plus through an iOS update in December. The company said it plans to extend the update to other products in the future, meaning newer models of the iPhone like the iPhone 8 and iPhone X may get similar tweaks.

How can I check my iPhone battery’s performance?

New iOS updates Apple plans to release this year should give people more information about their iPhone’s battery life. If you can’t stand the wait, you can download the Geekbench 4 iPhone performance-monitoring app from Primate Labs, which published research about the battery problems in December.

How can I upgrade my iPhone’s battery?

The easiest way to get a new battery is to schedule an appointment at your nearest Apple store’s Genius Bar. Depending on the length of the wait list and availability of replacement batteries, the process could take hours or days. If you instead mail your phone to Apple, expect a roughly five-to-nine day wait.

How can I improve my iPhone’s performance?

Avoid cold weather, if possible, since that can affect battery performance. Apple says that iPhones are designed to perform best at 62° to 72° F (16° to 22° C). Avoid leaving your iPhone out in the sun too, as temperatures over 95° F (35° C) can damage the battery.

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