I hope to find that out too. I managed to characterise the phenomenon a little. If the battery is draining faster than normal then the “Standby” and “Usage” nu

I hope to find that out too. I managed to characterise the phenomenon a little. If the battery is draining faster than normal then the “Standby” and “Usage” numbers under the battery settings page will be in lockstep, even when the screen is off. If you use the double-click-home task manager to swipe away all your “running” apps, then battery life will return to normal and the Standby time will be much larger than the Usage time at the end of the day.