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Sony has made a big deal of the Xperia M4 Aqua's two day life, employing a number of energy saving features – as well as pared back hardware – to accomplish this goal, and Sony claims that it is enough for 7 hours of high definition movie playback and 64 hours of listening to music.
During my time with the handset I found that generally the battery life was good – though uneven. Some days when moderately using the M4 Aqua for phone calls, texts and checking emails regularly, I'd end the day with the M4 Aqua still retaining an impressive 60% of its battery life – which means it would be easily capable of two day battery life.
However throw in some web browsing – both over WiFi and 4G – and the battery depletes much quicker, with a drop of around 20% after 15 minutes of browsing. So the M4 Aqua does do a fair job of holding onto battery life when used in certain circumstances, but not so well in others.
If you're worried about battery life then Sony has included a number of features to help preserve it. Extended standby mode acknowledges when the screen of the M4 Aqua is turned off and effectively pauses background apps that it assumes you won't be using. You can still receive calls, texts and alarms, and you're also able to exempt any apps you like.
You can also enable Ultra Stamina Mode, which cuts down the M4 Aqua's functionality to just the core features such as making calls and messages, which should give you enough time to reach a charger.
I found that these features worked well in helping prolong the battery life, and with careful use you'll be able to take the M4 Aqua away with you without having to worry about charging it for at least a couple of days.
When the battery life does expire, I was pleased to see that the M4 Aqua charges relatively quickly as well.
In our standard battery benchmark, where we play a high definition video for 90 minutes with the screen turned to full brightness, the battery drops by 25%, which isn't a bad result at all. Last year's Moto G lost 26% in comparison, however the more expensive Xperia Z3 Compact lost 33% of its battery in the same test, mainly down to its more power-hungry innards.
This means if you don't mind a slightly underpowered handset in favour of more battery life, the M4 Aqua is a really viable option.
Matt is TechRadar's Managing Editor for Core Tech, looking after computing and mobile technology. Having written for a number of publications such as PC Plus, PC Format, T3 and Linux Format, there's no aspect of technology that Matt isn't passionate about, especially computing and PC gaming. Ever since he got an Amiga A500+ for Christmas in 1991, he's loved using (and playing on) computers, and will talk endlessly about how The Secret of Monkey Island is the best game ever made.