Battery of Nexus 7 started draining I've had my Nexus 7 2013 for a few months. A few weeks ago, for some reason the battery started draining - it was empty after one day or so.

I the reinstalled whole tablet, and after that everything went back to normal, but after maybe 10 days I again faced the same problem with the battery. How can I find what causing this problem, and how to solve it?
Try seeing if a particular wakelock is preventing your phone from going into deep sleep, which can cause battery drain.

If you have rooted your device/can root your device:
You can use Wakelock Detector Free to diagnose wakelock problems. You can download it from the play store. Also make sure you have enabled system processes to be shown.

Once you are on the main screen, make sure CPU wakelock is selected (there is a chip on the top right part). If the bar on the top is mostly green, you don't have wakelock problems. If it is mostly red, you probably do. If so, select the first item on the list below. The first wakelock on that item is the culprit.

Now that you have identified the wakelock and the process responsible for the drain, google them to find out how to solve your issue.

If you have not rooted your device/can't root your device:
Try posting some screenshots of your battery statistics. Furthermore, use those battery statistics to help yourself identify the problem. Google "X app uses a lot of battery", where X is the app on the top of the list in battery statistics.