https://www.theverge.com/circuitbreaker/2019/1/16/18185283/apple-iphone-battery-case-size

Apple launched battery cases for the latest iPhones yesterday, and they have lower battery capacities than previous generations. As spotted by Wirecutter’s Nick Guy, Apple’s Smart Battery Cases for the iPhone XS and XS Max only have a 1,369mAh internal battery, which is the smallest in any of Apple’s battery cases to date.

The iPhone 7 battery case housed a 2,365mAh battery, while the iPhone 6 case contained a 1,877mAh battery. We still don’t know the battery capacity of the iPhone XR case, but Apple’s battery life estimates suggest it’ll be about the same.