I've experienced the same thing on my 5x that I did on my Moto X. Immediately after an OS update, battery life would tank. As in, dropping 10% per hour while

I've experienced the same thing on my 5x that I did on my Moto X. Immediately after an OS update, battery life would tank. As in, dropping 10% per hour while sitting on the table idling, or about that. I found on the Moto X that a Google service was chewing up a lot of power/battery. Upon rebooting, that service would return to being a very minor component of battery use. The first time my 5x started discharging in similar fashion, I had a look at battery use and found the same thing. Turning the phone fully off and back on, as with the Moto X, seemed to "fix" this. I'm not saying this is your problem. Unless you never restarted your phone after such an update -- waiting and charging my Moto X overnight was not enough to make it go away. But even if not, maybe this comment will help out someone else.