https://wccftech.com/iphone-12-pro-max-vs-iphone-11-pro-max-battery-capacity-leak/

The rumors continued to whisper that Apple would make changes to the battery capacities for the iPhone 12 lineup, with information summarizing that the value would be smaller compared to the 2019 iPhone 11 family. As it turns out, that is the case with the iPhone 12 Pro Max, which actually sports a smaller cell than its predecessor, the iPhone 11 Pro Max, according to a regulatory filing.

According to the information spotted by MacRumors at TENAA, a Chinese regulatory filing authority, the iPhone 12 Pro Max sports a 3687mAh battery, making it smaller than the capacity found in last year’s iPhone 11 Pro Max. In case you’re wondering, the iPhone 11 Pro Max features a 3969mAh cell, so that is a small decrease. Then again, there are comparisons of the iPhone 12 Pro Max, stating that Apple has incorporated a much larger primary camera module, so it’s possible this hardware upgrade took up a lot of the space that could have otherwise been used for the battery.