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  • Features a 3430mAh cell to power the Z5 Premium
  • Significant battery drop in our video test
  • Not good enough battery considering it has a 4K screen to power

The Sony Xperia Z5 Premium comes with a 3430mAh battery pack, which sounds like quite a lot – and it is compared to some other smartphones. But remember, this phone has the highest-resolution screen on the market, and that demands some serious power.

That poor little cell has to power all those pixels over that 5.5-inch display, and even if you just turn on the screen briefly to check the time everything needs to light up.

It's four times as much work than that on a Full HD phone – and the Xperia Z5 Premium doesn't offer good enough battery life to match that 4K display.

Sony Xperia Z5 Premium

I regularly finished the day without any charge left in the Xperia Z5 Premium – most days it would die on me around 9pm, and that wasn't after particularly high usage during the day.

If I'm just listening to music and keeping the connectivity options on without lighting the screen, then the battery life is about what you'd expect from a current phone – but if I do anything that involves having the screen on, it drains quite quickly.

Put through techradar's standard 90-minute video test, the Xperia Z5 Premium came out with a disappointing 69% of battery power remaining, a drop of 31%.

For comparison, Samsung's Galaxy S6 Edge+ boasts a 5.7-inch 2K display and completed the same test with a drop of 23% – and we were disappointed with that score at the time.

Add into the mix the iPhone 6S Plus, which lost 22%, and the Xperia Z5 Premium's showing starts to look a little embarrassing.

I then ran the test again with brightness at 60%. I wouldn't usually watch films at such a low brightness setting on the Xperia Z5 Premium, as the picture is nowhere near as vibrant, but we run this test to see how much battery life you can save by turning down the screen brightness when maximum brightness isn't essential.

The Xperia Z5 Premium disappointed again here, coming out with 73% of its battery left for a drop of 27% – that's a bigger drop than the Galaxy S6 Edge+ recorded in the full brightness test.

Sony Xperia Z5 Premium

Given such poor battery performance, it's a good job that Sony has at least included fast charging technology in the Xperia Z5 Premium.

You'll need a special charger to be able to use this – however, you don't get one with the phone, and we didn't receive one with our sample handset, so we can't comment on its efficacy yet.

It's disappointing that a fast charger isn't included in the box. When you're asked to pay this much money for a phone you'd expect Sony to stretch to an accessory that's integral to a good experience with the device.

If you want to buy the fast charger it's called Quick Charger UCH10, and you can get it from a few sources, including Sony's website, for £19.99 (about $30, AU$42).

According to Sony, fast charging brings your battery up to 60% in 30 minutes, and if that's true it certainly makes up for the shortcomings of the battery, and will enable you to enjoy the 4K display without worrying about running out of juice.

Sony has also – yet again – left out wireless charging technology. This was really the time for Sony to include the technology in its phones, with charging facilities starting to appear in coffee shops, cafes and bars in many cities.

Battery life is proving to be the biggest concern for mobile users, and it's a real disappointment that Sony didn't go further in offering more and better charging options before amping up the screen resolution.

It just goes to heighten the suspicion that Sony has made a 4K phone simply to enjoy the bragging rights that come with having the highest-resolution screen in the mobile world.