The phone uses two battery cells to provide a total energy of 10.35 Wh (2716 mAh at 3.81 V) battery, comparable to the 10.28 Wh of the slighly smaller iPhone 8 Plus (but less than the 12.71 Wh of the Samsung Galaxy Note 8)
This mostly gives more flexibility for the 20 layer multi-board design to accommodate the two camera depth sensing imaging system.
There are two different models for different regions with different power management devices. The A1901 supports LTE and UMTS, While the A1865 adds CDMA and is likely to be the Qualcomm version with its WTR5975 gigabit LTE transceiver with the MDM9655 Snapdragon X16 LTE modem its PMD9655 PMIC, the same as the iPhone 8. The A1901 is using the Intel broadband processor PMB9948 and the Intel PMIC, the PMB6848.
Apple’s 338S00306 power management IC is developed with Dialog Semiconductor for the same A11 Bionic applications processor that is used in the iPhone 8 and 8 Plus.
So far there is no sign of the Broadcom BCM 59355 wireless charging chip used in the iPhone 8 platform but the X supports the same Qi standard with the same performance specifications and the chip was a custom development with Broadcom earlier in the year so it is expected to be present in the design. How this will fit with the recent acquisition of a TI-based wireless charging company remains to be seen.
The fast charging capability that provides 50% battery charge in 30 minutes via USB-C was tested on pre-production charger models, the 29W A1540, 61W A1718 and 87W A1719. The controller for this has also not yet shown up in the initial teardowns.