Re: Battery Life
Xiaomi Redmi Note 3 also has 4000MaH battery, and I get a good 2 to 3 days from a single charge.
Battery life depends entirely on how you use your phone. I have an original Moto G (now running Cyanogenmod) which has (I believe) a 2,000mAh battery, and when I recharged it last night it had been nine days since the previous recharge. I get worried if it's been under a week.
But then I only turn on the WiFi or the data or the GPS if I'm actually using them and (crucially) the phone gets an occasional reboot. There are one or two apps that once loaded, even if no longer in use, seem to drain the battery. Rebooting is a good way to kick these out.
A side-effect of fewer recharges is probably also longer battery life as Lithium batteries are limited by recharge cycles.
That suits my own use of the phone - for phonecalls and texts and the occasional snapshot or a bit of web browsing (I won't count tethering as doing so via USB doesn't drain the battery). I realise others make much more use of their phones' fancy functions, so of necessity use more juice.
M.
Biting the hand that feeds IT
