I don't think it's fair to compare an iPad Mini of any kind to an iPad Air of any kind when it comes to battery life. With its larger size, the Air will of course come with a significantly bigger battery, which will skew the results. That's like comparing a 6S with a 6 Plus; no matter what kind of power saving technology they put into the hardware or software of the 6S, it will be hard-pressed to overcome the physical disadvantage of having a much smaller battery than that of the 6 Plus.Find my thread with a review and descriptive comparisons to a mini 2 and Air 1 for the mini 4 on macrumors.
I am just not getting the best battery life like I do on my Mini 2 and Magic Air 1. with minimum usage on my Air 1 from most recent full charge, I got over 10 hours usage and its now at 50 percent. I am looking at another 8 to 10 hours usage time with screen on and only web browsing, some music, all loading and closing apps, speed tests, and YouTube video here and there.
All of a sudden I am getting mystical battery life on my mini 2 and Air 1 because the only reason I have used them at all now was to compare everything side by side to the mini 4. I game a lot but since getting the mini 4 and trying to tweak it for the best battery life and cloning settings to match my other iPads, I have been using it 24/7 and not the other ones except for testing.
Usually Mini 2 IOS 8.4.1 = 11 - 13 hours and 15 minutes screen on time with 50-75% gaming and 25-50% safari web browsing
Usually Air 1 IOS 8.2 = 13 - 14 hours and 50 minutes screen on time with 50-75% gaming and 25-50% safari web browsing
Unusual Mini 4 IOS9 (maybe the culprit) = 10 hours 37 minutes screen on time with 25% gaming and 50-75% safari and 25% misc like music, YouTube, photos, speed tests and so forth.
Mini 4 has new auto brightness sensor and software mode for it in IOS9. I got the Gold 16gb wifi version and the brightness does some crazy stuff. With auto brightness on any ambient light change in environment you use tablet in the auto brightness on mini 4 and IOS9 instantly brightens the screen some times too much compared to how the mini 2 worked with auto brightness and IOS 8. If light dims in environment IOS9/Mini 4/sensor dims screen which I like that it does this now compared to older IPADS and IOS 8 and below, EXCEPT its doing it all the time, instantly not gradually.
Do not know if I got a dud or all new mini 4's do this. ALSO with that in mind, I disabled auto brightness and set brightness to a specific level. I do not know if its a BUG/GLITCH/IOS9 or hardware issue but the brightness will stay where I have it set but still will dim lower or back to where its set with auto brightness off in certain IOS9 stock apps. Like Safari I was replying to a thread today on the mini 4 with auto brightness disabled and setted it a little over low brightness. Well clouds came in where I live and darkened room, so the set brightness I had it on while typing in a forum thread in Safari dropped the dam brightness on me, then when room brightened back up, brightness went back to where I specifically set it at with auto brightness disabled. ITS SO DAM WEIRD!!!!!!!!!!!!!
This has to be hurting battery life and performance. Also I think touch ID sensor always enabled and on hurts battery life since Air 1 and Mini 2 do not have it, Also mini 4 has a barometer which no app uses built into IOS9 that I know of and it probably always enabled and being used for who knows what reason.
Whole reason I jumped ship from Android was for 1. Performance 2. Battery life 3. Screen resolution and quality 4. Sound & Audio 5. Wifi performance 6. Lightning accessories 7. Overall smoother and lag free experience and better app optimization to include performance and eye candy compared to android counter parts. AND in IOS8 no dam battery life draining due to stupid 3rd party apps doing what they want without your permission.
MY AIR 1 gets 15 hours GAMING and browsing before I got to charge it again. No android device from any company can out do that. IT also beats it in web browsing performance bar none even out doing laptops. A7 and 64bit architecture does help apple IOS fly. That is of course 8.x versions. They got a long way to go to get IOS9 to not only run as smooth as IOS8 but to optimize battery life and fix all the weird bugs and glitches and crappy coding they left hanging.
IOS9 keyboard on mini 4 is always doing stuff when I get going typing on it very quickly, touch response is there but keyboard in IOS9 wants to do its own dam thing like its got a mind of its own....
IOS8.x keyboard does not do that and keeps up with me going bananas typing so dam fast on it! Of course my Air 1 and Mini 2 have older touch response and air gap and layers between everything in screen.
Mini 4 does not, and some times I think there are some touch issues when I am sliding back and forth to different web pages in memory in safari for navigation. My MINI 2 and AIR 1 do not do this. Once again is it hardware, glitch, bug or just crappy IOS9. who knows?
I had mini 4 for almost now a week, I got another week before I'm allowed to return it.
I do love the screen, the performance and the smoothness and refresh rate of screen during games with high fps or videos. ALSO SAFARI flies browsing heavy websites scrolling through long ones instantaneously. (Maybe new version of Safari using the Metal API as Apple claims for better browsing drains the battery more compared to older models and IOS9; because that is what I have been using/doing most of the time on the new Mini 4)
I just do not have the time to figure out if it is hardware issues and defective on the model I got, if I do not return it then I am stuck with it. But if its IOS9 then of course I can wait on Apple to hopefully fix it. Although not many others on these message boards have shared in depth reviews or comparisons that are technical and analytical in detail to help me figure out if I got a lemon or not!
Link to mine: https://forums.macrumors.com/thread...-with-idea-of-downgrade-to-ios-8-4-1.1918669/
Link to battery life: https://forums.macrumors.com/threads/mini-4-battery-life-ios9-build-340-results.1919763/
Your iPad Mini 2 vs Mini 4 comparison would be more fair, but when you're not comparing everything at literally the same (same OS, testing under same conditions while doing the exact same thing), the results are not going to be accurate. Despite iOS9 supposedly helping battery life, in general I believe Apple rated the Mini 4 around 10 hours of battery life while surfing on Safari, and it seems you're getting around 10 hours now. Touch ID's battery drain is insignificant as it was also available on the 5S and I didn't see any appreciable difference in battery life between the 5 and 5S.
The keyboard issue is strange though, and I haven't noticed that on my 6 Plus on iOS 9.0.1 or my iPad Air 2 on iOS 9.1 beta. I would suggest, before you return/exchange it, to restore to factory settings (if you didn't do that already), then set it up as new and add the apps back in one by one. If you restored from back-up, you might have gotten some weird issues with settings or whatever that didn't play nice from one OS to another. If you didn't... well, doesn't hurt to try...?