Battery is the biggest bugbear for a lot of phone customers, and the Xperia Z5 isn't going to be their saviour. Sony has decided to shrink the battery yet again down to a 2,900mAh cell, as it clearly thinks the optimization on the phone is getting better and it's more important to have a slim device rather than a high battery life.

I'd disagree, and when you look at the lifespans I was getting out of the phone there's no justification for downgrading the cell size. Sony should be upping it.

The Xperia Z3 came with a 3,100mAh battery which the Xperia Z3+ cut down to a 2,930mAh and now it's even lower.

Xperia Z5

The Xperia Z5 has some serious improvements upon last time. General life is definitely better than the Xperia Z3+ but it's not as stunning as Sony would like you to think.

On average, I get a full day out of the battery. On particularly heavy usage days, it would be about 7pm when the phone kicked the bucket.

I ran our 90-minute video test on full brightness with all connectivity options, and it came out with 75% of its life left. That's not fantastic, but it is a major improvement upon the last two phones from Sony. The Xperia Z3+ came out the other side with 62% whilst the Z3 had 69% leftover.

I ran the same test but with brightness down to half to see how much of a strain the screen is. This time it had 82% charge at the end of the video.

Sony Xperia Z5 review

It's good, but considering the Galaxy S6 only dropped down to 84% on the full brightness test – and that's a 2K display – it's not the best you can buy right now.

When gaming, the battery drops more drastically. In an hour long test of Real Racing 3 the phone dropped from a full charge down to 59%. The Z5 can't match the five hours of gaming that the Samsung Galaxy S6 offers.

I also put the Xperia Z5 head-to-head with the Samsung Galaxy S7, LG G5, iPhone 6S, HTC 10 and Huawei P9 in a video test of their web browsing skills, which you can check out below.

With each handset running at full brightness and using a web script to continuously cycle through sites, the Sony Xperia Z5 had dropped to 73% battery after one hour and 40% after two, which put it in the middle of the pack and well below the HTC 10, which topped the test with 56% battery left.

That's not an awful result though, it pipped the LG G5, which had 39% left over and was a far stronger performer than the iPhone 6S, which was left with just 22%.

In summary the battery life has improved on the Xperia Z5, but it's not the best it can be. The competition is doing similar if not better and considering this is a big claim of Sony's latest marketing campaign I was really hoping for something better.

Sony has opted to leave out fast charging technology from the Xperia Z5 as well and I think that's a mistake. Manufacturers such as Samsung and Motorola have put a focus on fast charging technology to improve their battery reputation and it feels Sony is just sitting around waiting for something to help out.

The battery isn't impressive on the Xperia Z5 but it would have been vastly improved if I can get it to half way charge in 15 minutes of being connected to the wall.