Just to describe my experience first. After update my battery was going from 100 percent to 20 percent in about 8 hours while idle. It wouldn't charge while it was on. I would have to turn off the phone to charge it. I could not figure this out, until I found similar issues on different phones in the forums. It seems that when an update gets pushed to your phone, and your battery is low, your current battery charge is cached as 'max'.
First I thought the connector on my charger was broken. Then I thought maybe the charge port on the phone was somehow damaged. Then I thought there was possibly a foreign object in the charge port. It is actually none of these things. It's a software issue. Here is the resolution.
You want to boot into recovery mode. This is taken directly from Lenovo's website on the Turbo 2, but please read my caveats at the end.
Power off the device and unplug it.
Press and hold the Power and Volume Down buttons until the device turns on.
From the Boot Mode selection menu, press the Volume Down button to scroll to Recovery and the Power button to select it. The device will restart.
An image of an Android robot with a red exclamation mark will appear.
Press and hold the Power button, while still holding Power, press and release the Volume Up button, then release the Power button.
Use the Volume buttons to scroll to Wipe Cache Partition and press the Power button to select it.
If an additional confirmation screen appears, use the Volume buttons to scroll to Yes and the Power button to select it.
Press the Power button to select Reboot System Now.
This is basically the process, but you have to change up a couple things. After you wipe the cache, select 'turn off' rather than 'reboot'. Give the phone a minute to be sure it is entirely off. Plug the phone into a charger in the off state and let it charge fully. Once you are certain that the phone has been charged to 100 percent, you can reboot phone. Voila, back to almost 2 days worth of battery life.