I think I have to return my set. It's probably a refurbished set. I still couldn't fix the high battery drain issue.
So as an experiment , after charging to 100%, I immediately put it in Ultimate Power Save Mode and noted the 'No. of hours Left' info displayed on the phone. It showed 122Hrs ++min.
After 5 hours I checked the screen again, it showed 113Hr ++Min left.
By right it should show approx 117Hr ++Min (122-5).
In just 5 Hrs , I already lost an additional 4 hours of Battery time (Total 9 Hrs Battery time lost)
At this rate if I keep the Phone in Ultimate Save all the time , it will last me less than 3 days.
This must be record for lowest battery life for a 5,100mAh phone, lol. Can compete with a 2,000 mAh phone

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update
I checked Lazada's rule for returns, it states I have to inform them within 48 hrs of intention to return. And also this item only has 7 days return policy. Looks I like I am stuck with the product.
This post has been edited by Ngto: Sep 13 2017, 10:24 AM