Charge it up all the way and let it stay on battery a couple hours. In the meantime, I would recommend downloding "Wakelock Detector". Once your phone has been running on battery for a while start the Wakelock detector app and select the setting from the top right called "CPU wakelocks"
My phone gets great battery life after some tweaks and have found that you will need to pinpoint the exact issue that's keeping your phone awake. I'm assuming your phone is never going to sleep.