Discussion died for some reason? I don't feel like going through many pages of reading, sorry.
A quick search showed no info on the battery so I'll add it: it is a 51x51x6mm 3.7V 1950mAH battery. Almost no room for something that's even 52x52mm. Looks like a bigger version of what my J3 has. So anyone wanting to replace the battery himself later should take these numbers into account. Replacing the battery will require removing three 1.27mm hex screws: one by the USB socket and two covered by plastic squares at the top (remove these squares with a safety pin), the factory leaves the screws on very tight. The screen together with the motherboard and battery and all must be carefully wedged out then, make sure to remove your SD card prior to trying to wedge it out to avoid the risk of damaging, along with the device being off, of course.
The battery's leads (one white, one brown) are terminated to a tiny Molex-like connector; you'll probably want to snip it off and carefully reterminate a new battery with it so the battery can be plugged into the male socket on the motherboard. Heatshrink/liquid electrical tape will be needed to shield the joints from each other and Z2's internals. I forgot to check the polarity of the leads.
Also, I can't download applications at all from the Play Market without the Market instantly crashing if I try.