Battery life on the Sony Xperia Z3 borders on the exceptional at times. Sony claimed to me that this phone could last two days on a single charge in 'real use' - a lofty claim indeed.
Of course, it can't live up to that level - but then again, I've never come across a phone that has ever been close to manufacturer's claims.
In reality, without Stamina Mode activated, you'll comfortably get through a day. With it turned on from 65% (as I had) you'll get easily into another day and maybe trickle into two if you're really careful.
However, it's not perfect, as it does show the standard 'quick drop' of power if you're using the screen too heavily, even on average brightness.
But let's place this in context: compared to something like the iPhone 6, which has a 720p display (roughly) compared to the Full HD offering here, and the Z3 still manages to outscore the iPhone in terms of video and gaming ability when it comes to battery life.
This shouldn't come as much of a surprise, given the Xperia Z2 did so when in the world of battery retention - although the fact the non-removable battery is now smaller (at 3100mAh) compared to its predecessor but still manages to last longer shows that Sony's mysterious screen technology is working.
I say mysterious because the brand won't really talk about it. There's some element of the screen 'remembering' what's on there, rather than constantly refreshing all the time, but I have no idea if this trick can be used in movies or whether it's limited to more static web browsing.
Stamina Mode isn't a new idea from Sony, having arrived on the original Xperia Z, but it's still a useful feature, if not a frustrating one at times.
The theory is simple: the Z3 goes to sleep, the phone then cuts all connectivity to apps (apart from those that have been whitelisted as able to connect during sleep) and the battery is thus preserved. The downside is that you don't get updates instantly, the upside is fewer disturbances and a longer battery life.
On the whole, it works well. However, there were a few instances where I was alerted that Spotify or Real Racing 3 were preventing the mode from working (even though I wasn't using them), thus nullifying the battery savings.
Why were these apps running in the background anyway? And if they were, why didn't Stamina Mode shut them down? The same option will truncate the frame rate in gaming, leading to a juddery experience that I accepted at the reward of more battery power.
If that's the case, then the phone should be able to shut down or at least hibernate apps - I don't want to be told that this feature doesn't work, I want it fixed.
The same for the heavy power saving mode the Z3 has embedded: like Samsung and HTC, Z3 owners can now flick a switch and have only the most basic of functions work, allowing you to have maximum battery and make a few calls and texts.
When turned on, it takes an age to boot the phone into the mode, and even then I saw very little power saving, with the device still running low on juice almost as quickly as when the phone was on normally.
It also doesn't seem to do much more than limit the data and apps you can use, although presumably all the cores are turned right down. It's like it needs some time to warm up – if your battery is falling, it won't arrest that slide, more bring it to a controlled slow-down.
In terms of TechRadar's battery test (a 90 minute Full HD looped video), the Sony Xperia Z3 on full brightness is a real power guzzler – at 31%, that's one of the poorest showings from any phone.
But, and this is a very important but, the phone can go brighter than most other handsets can manage, which is a choice you'll need to make at the expense of a wider gamut of places you can use it and thus accept the drop in power to get a really good screen.
What's interesting is that even at lower battery modes, the power savings aren't that great. This tells me that it's the screen 'remembering' tech that's the battery saver, which obviously can't be used in video.
The other niggle is getting power back into the battery. It charges rather slowly at times, even with high amp charging blocks, which is most irritating seeing as many modern smartphones are able to juice up in minutes - the iPhone 6 is practically 'blink and you'll miss it' speedy when it comes to charging.
Rumours for the next Sony Xperia handset suggest an even larger battery than before. On the Xperia Z4 we're expecting to see a 3,400mAh cell but it depends on the rest of the set up whether it'll be perform better than the Xperia Z3.