Initially my battery was okay but in the process of using tablet, I have noticed inconsistent battery readings. Sometimes battery drains fast until certain percentage and then it stops at certain percentage for 20 minutes and then drains very fast again. For average activities like surfing internet, chatting on Skype and excluding videogame playing and movie watching, battery lasts me 4.5 hours which is subpar for 7800mAh battery. I have upgraded ROM from stock Android 4.1.1 to 4.2.2 rooted and this case with battery did not change.

What can can I do to restore battery to optimal status? Should I gauge battery by deleting battery stats in Android ROM or something else? Where can I get new quality battery for PIPO Max M9? I saw it in chinese online stores but I want something better than stock battery I have got my tablet with.

Thanks.