I got this battery a few days back, and i havent done a FORMAL test, however in my regular usage (with 4g on, casual browsing, facebook chat, whatsapp chat, syncing 1 gmail email, and various apps, listening to music, sometimes videos). I would only get a few hours on the stock battery like 3, maybe 4 hours. With this new battery i have not still gotten nowhere near 0%. After a full days use, from 9 am to 11:30 p.m, i still had 40% battery left. And to give an even more recent measure, i unplugged my phone from the charger at 8:30 a.m, and listened ot music on my way in to work, and have had it idle, it is now 12:30 p., and its at 86%. so 14% in 4 hours is pretty good. This battey last about 2 to 3 times longer then stock battery, pretty much the whole day. It is of course much bigger then stock battery. The back cover isn't as gripable as the stock battery cover. But overall it lets me use my phone normally now, where i can actually be out all day and come back home and still have a subsnantial amount of battery left. 36 hours is probably right for this phone, i saw it in another review.