The iPhone 6s is still a great device for its age, but as it turns out, that’s only true if your battery is in good condition. Otherwise, Apple’s iOS algorithms automatically slow down the handset to prevent unwanted shutdowns.

We already know iPhones that are slowed down will score a lot lower in benchmark tests than they should. That’s how someone discovered Apple’s secret iPhone throttling in the first place, which turned out to be quite the scandal for the company. Dozens of class action suits and various government investigations emerged in the wake of the revelations, even though Apple has taken some steps to address the matter and to appease customers.

But a new series of speed tests show us how slow an iPhone 6s with a chemically aged battery can get. Spoiler: It’s not pretty.

Remember all those speed test comparisons that we see on YouTube on a regular basis? Usually, we’re looking at the best Android devices being compared to the latest iPhone. These traditional “real life” speed tests involve opening a set of predetermined apps on both phones to see which one is faster.

YouTube user Bennett Sorbo applied that technique to his iPhone 6s, comparing the phone’s speed before and after a battery replacement. As you’ll see in the clip below, the iPhone 6s that’s throttled is significantly slower when performing the same exact tasks as the same iPhone 6s with a brand new battery.

I understand that Apple wants to prevent iPhone shutdowns with by slowing down iPhones with batteries that need servicing. But in real life usage, a throttled iPhone performs a lot worse than you’d expect. It’s certainly worse than Apple would have you think.

“iOS dynamically manages the maximum performance of some system components when needed to prevent a shutdown,” Apple said in an apology letter late last year. “While these changes may go unnoticed, in some cases users may experience longer launch times for apps and other reductions in performance.”

Check out the clip below, and see for yourself whether you notice the changes.

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