iPad mini ios9.1 Heavy battery drain

Hello all,

I have purchased a new ipad mini ios7.1 from apple authorized store. It was working fine and great. After I updated to ios9.1 i am facing heavy battery drain on my iPad. I even deleted my app and installed it. but still the battery get drained 1% for every 7 minutes when the wifi is ON state. Even I disabled many options which are available such as location, background app refresh, auto brightness. I brought only three months back (on aug 2015).

I have given my ipad to service center for replacement and asked them for assured replacement. But they said that they will go for battery test and say the result. what my question is.. will they replace my iPad with new one? bcz the battery is draining unconsiderably . Then what is my alternate option if they don't replace.

So people around the world share your thoughts and idea..