Microsoft has released another system firmware update addressing the ongoing issues with models of the SP3 using the Simplo battery:

Surface Pro Embedded Controller Firmware

• v38.10.90.0 corrects an error that may occur on a limited number of Surface Pro 3 devices where the full charge capacity of the battery is misreported to the operating system and device firmware. This update corrects the firmware component that functions as a “fuel gauge” so that the battery capacity is accurately reported. See Surface Pro 3 Battery FAQ for the 8/29/2016 System Firmware Update for more information.