On Thu, 18 Jan 2018 03:17:21 +0000 (UTC), Harold Newton wrote:

"We will tell someone we're reducing your performance ...and if you
don't want [reduced performance], you can turn it off."

"Apple's battery throttling techniques is activated on iPhone 6,
iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, iPhone 7, iPhone 7 Plus
and iPhone SE as of iOS 11.2. It reduces performance by 50%."

https://9to5mac.com/2018/01/17/turn-off-iphone-battery-performance-throttling/