Are your apps up to date? How much do you have running in the background? Any LTE/Data network heavy services?
I would use an app called CPU-Z and throw it into multi-window mode to see if any particular app causes the CPU usage and all clock speeds of the cores to spike up drastically. Also, if you have any games that are sent to the background (home button) rather than closed (back button), this may be a drain on the battery.
Also, if you have any task killers installed, please remove them.