I have read good things about the battery on the G3. I'm curious are speaking from owning this phone or just speculating?
I picked up the G3 last Saturday and have been using the crap out of it since getting it so I can get a good feel for the real battery life before my exchange period of 14 days is over. I'm struggling with keeping it, or getting the M8, which is why I'm being so hard on it with testing the battery. Anyway, here's my findings over the past week...
Things that do not change: I use Google Now with ALL the bells and whistles turned on, I sync my Gmail stuff (contacts, mail, calendar, etc), I have pictures auto uploading to Google Photos when on wifi, I do not have bluetooth on, I do not have NFC on, I have Facebook and Twitter on 1 hour sync schedules, and I have other apps that sync manually like Evernote and Kindle, I have GPS set to high accuracy and it's on all the time because I love Google Now and hate constantly swapping it on and off, etc. I have no rooted, no custom ROMS, I've disabled Smart Notice and the extra "G" home page, still using LG's launcher.
1. Day after I got it, I was out of the house with the wife and kids most of the day. On 4G (not LTE, not worth the drain in my opinion) and outside most of the day with auto-brightness, 4 hours and 18 minutes of screen on time. This was a bit of GPS, social networks, some camera stuff, minimal games, minimal texting, 1 5 minute call, etc. I was not happy with that screen time, however I will give it credit in the fact that I took it off the charger at 3am and when I woke up at 10:30am, it still showed 100% battery.
2. Monday - Today I have been in my house exclusively. I work from home, and I work nights, so I don't get out much during the week and while being on wifi all day with auto-brightness off (keeping it at 20-30% depending on the room, auto goes on if I step outside to grab a smoke and back off when I come back in) since I'm in controlled lighting, I'm averaging 4:50-5:30 screen on time. Minimal texting and like 2 calls all week, lots of browser, lots of social networks, good amount of camera, some gaming to test performance but no marathon sessions.
My conclusion so far is that the following:
1. Standby time is freaking amazing. I have no worry about charging to full before bed and leaving it off charge all night. I go to sleep at 100%, I wake up at 100%. My sync habits are listed above, and even with those habits, it still maintains 100% charge during my 6-8 hours of nightly sleep.
2. Screen on time is extremely hit or miss. Wifi and not using auto-brightness with the screen at 20-30% brightness gives a very respectable 5+ hours of screen on time to compliment the stupid long standby time. If you are spending a lot of time away from wifi and you're outdoors with auto-brightness, or worse, manual 85%+ brightness, the screen time drops noticeable as shown by my first day findings of only 4 hours 18 minutes (that was to death, it died on me while I was checking the screen time for the last time, literally). That day I was out and about for a good 4-5 hours, so I imagine if it was an all day kind of thing it would have been below 4 hours.
I've noticed that once you get over 50% screen brightness, especially outdoors, the device heats up fairly quickly, but doesn't become uncomfortable and I haven't gotten the dreaded throttling pop up yet. Above 50% brightness the batter takes a noticeable hit as well, and it is sensitive to light so auto is way harder on the battery than manually adjusting brightness indoors and only turning auto on when you're outdoors. On the days when I'm home working, I'm pleased with the 5+ hours screen time and huge standby time. But, my experience last Sunday where I barely eeked up 4 hours 18 minutes and I wasn't even gone for a FULL day has me worried. I'm actually going to an amusement park with the family this Saturday and it will be an all day affair so that should be a good true test of screen time when not in the ideal scenario of my house. If it doesn't hold up, I'm taking it back and getting the M8. I'm just super concerned about the M8's camera... I don't do a lot of artsy photography or take a lot of landscapes, but I do take a ton of pics of my kids so it is important that the camera work well.
Lastly, I have NOT seen any serious lag this week. I'm concerned about battery life, but overall from a performance perspective, it has been fine. Like I said above, I'm not using anything custom, I'm not rooted, I have a few apps disabled the normal way that everyone can do, and I'm still using LG's launcher and I've had no serious issues at all. A few hiccups here and there, but honestly, nothing worse than the Nexus 5 I used to have despite all the comments in this thread talking about how buttery the Nexus 5 is compared to this. The only slowdown I've experienced is when playing the original "Don't Tap the White Tile" game and I'm not sure why. I get no lag in games like Asphalt 8, or for direct comparison, even in the knock off White Tile games, just the original. I'm assuming it's an app problem, not the phone itself.