Well if you already did a wipe data factory reset then you already cleaned the system, so deleting batterystat.bin might be pointless. Anyway batterystats.bin is in /data/system you need a filemanager and root, wait till the phone dies, charge the battery while phone is switched off. letting the battery discharge isn't a good idea, but we're trying to recalibrate it.
If it still drains try to flash the phone again with miflash and check if some app wakes the phone even if it's locked (there's thousand of apps that accomplish that goal)
Last option buy a new battery.