While they hide some great secret features, even Apple AAPL -0.74% has been forced to admit its new iPhone XS (details) and iPhone XS Max (details) were shipped with problems. The good news is Apple fixed most of them, but new tests confirm there is one it can do nothing about…

Putting to bed questions about real-world performance, popular YouTube site PhoneBuff enlisted the help of robotics and discovered that for all the iPhone XS and iPhone XS Max’s incredible CPU performance, battery life is a mess. Particularly the bigger model.

What PhoneBuff discovered is the iPhone XS Max, the largest and most expensive iPhone ever made, couldn’t get close to the battery life longevity of its primary rival: Samsung’s Galaxy Note 9. In fact, when the iPhone XS Max died the Note 9 still had a massive 37% battery life remaining.

This is a shock for several reasons.

Firstly, while the Galaxy Note 9 has a larger battery, it’s only 20% larger (4,000 mAh vs 3,174 mAh). Secondly, the Note 9 has a higher resolution display and driving pixels is the most demanding thing a phone does. Thirdly, the Note 9’s Snapdragon 845 chipset is less efficient than the remarkable Apple 12 chip in the iPhone XS Max.

All of which points the finger at software. Apple claims iOS 12 is the fastest and most efficient generation of iOS to date. Apparently not.

But what makes these tests so interesting is PhoneBuff’s attention to detail.