How to access battery level when running Windows from Boot Camp?
By Apple Khmer, 8 December, 2016
Other Apple Chat
How can I get the WINDOWS partition of Boot Camp to correctly announce the battery percentage? The batter percentage is way off, and the battery meter never says charged after the battery is charged.
This is normal
What you're seeing is a difference between how Windows and Mac OS display your battery stats. When your Mac is constantly plugged in, to prevent damage the power supply occasionally turns off so that the battery can discharge a small amount. If you do this long enough then you'll see your battery percentage going under 100%, but this doesn't mean your AC adapter or computer is broken. If you're unsure, unplug your Mac, run it down a bit, then plug it back in and you'll see your battery go back up to full.
Regarding the differences between Mac and Windows, you'll see this effect on the battery on every Windows laptop, not just Bootcamp. So Windows is being a little more honest as to what's actually going on. My guess is that Apple is hiding this information as to prevent confusion for new users to avoid getting a lot of macs with supposedly broken batteries or chargers. Also, if you see your battery draining faster on Windows, this is also normal as Mac OS is a lot more optimized for the hardware.
Try hitting shift + incert + B.