OK I got some feedback from our Zesty overlord.
It appears the battery problems are due to calibration errors.
These are the instructions they gave me to recalibrate the battery:
This happened due to the battery not being calibrated properly after flashing the firmware which is normally done in the factory. Simply remove the battery for a minute and shake it (this moves the lithium around the battery to maximize battery cycles), then pop it back in and charge it fully while it is off. Once fully charged turn the phone on and drain the battery through normal use until it reaches 15% then charge it fully while the phone is on. Drain it again to 15% and charge it fully. This should re-calibrate the battery for you and maximize each battery cycle
I have done the first part of it. Just need to wear drain it to 15% now.
Hopefully this might improve battery life as well