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This is Everyday Science with Clare Wilson, a subscriber-only newsletter from The i Paper. If you’d like to get this direct to your inbox every week, you can sign up here.
Hello and welcome back to Everyday Science.
I’m going out after work tonight and I’ve just noticed that my phone is too low on juice to last the evening. I can’t put it off any longer – I need to upgrade.
It’s a common problem. When out with my friends, someone is often complaining that their phone is about to die – no matter how new it is.
It’s puzzling, considering that most other aspects of technology are improving at breakneck speed. Phone batteries, in contrast, sometimes feel like they are performing worse than ever.
Why is it so hard to get a phone to last through the day, and is there anything we can do to help it out?
Smartphones use lithium-ion batteries, the arrival of which 40 years ago were one of the breakthroughs that made mobile phones possible, and earned their three co-inventors a Nobel Prize for chemistry.
These kinds of batteries need to be rechargeable, and store enough energy to power a small computer, bright screen and multiple other gadgets in a device small and light enough to fit in your hand.
Today’s smartphones still use more or less the same kind of lithium-ion batteries as the first ones, but their efficiency has been improved in several ways.
The net result is that the amount of charge their batteries can hold has doubled in the past two decades. Even more impressively, the cost of making those batteries – a crucial limiting factor in phone design – has shrunk to a tenth of what it was, per unit of charge that they can store.
So, why don’t our phone batteries last for much longer than they used to? That’s because the energy demands our devices make on those batteries have been rising at about the same pace. “We are doing so much more with our phones,” said Professor David Howey, a battery engineer at the University of Oxford.
Screens have become bigger, brighter and have faster refresh rates. As well as connecting with the mobile network, smartphones now also have Wi-Fi and Bluetooth capabilities.
Keeping up the Wi-Fi connection is particularly power-hungry, especially if you are far from a base station. So, if you are somewhere remote it may be worth manually turning off Wi-Fi, said Howey. “If I’m away and turn off my Wi-Fi completely, my battery will last a lot longer.”
The increasing use of AI in features like photo processing and predictive text is also a power drainer.
A further change is that we now typically hold on to our phones for longer before buying a new one. The first “dumb phones” were often upgraded yearly, then two-yearly upgrades became the norm, and now we may hold out for three years or more before forking out for a newer model.
That’s mainly because the rapid pace of improvements in the tech has been plateauing, so there’s less benefit from frequent upgrades. Phones have also got more expensive and people want to get their money’s worth from each upgrade.
But while most of the other features of our phone can last three years or more, battery-charging capacity slowly worsens over time, so we notice that deterioration in the last year or two of its life.
You can check on how your battery is holding up by looking at a measure called “battery health” in your settings. After a couple of years it might be reading 80 per cent, which means that even when your battery is fully charged it will be holding only 80 per cent of the energy it could when it was brand new.
Something that speeds up this deterioration is letting batteries get too hot, so when the weather is like this, make sure you don’t leave your phone in the sun. And the charging process warms up the battery, so never leave it plugged in while tossed on the bed – make sure air can circulate.
You can also be strategic in how you charge up. When your battery is on 100 per cent or 0 per cent “that’s when things start to warm up, and that is what accelerates the ageing,” said Dr Royce Copley, a data scientist at Sheffield Hallam University.
Newer devices often let you choose a setting so the phone automatically won’t take your battery up to 100 per cent – something I will be sure to select when I get my next model.
Of course, manufacturers are constantly trying to make improvements. There is lots of potential here, as research last month showed that all this time, we may have been misunderstanding how lithium batteries work at the chemical level.
This suggests that in the future we could make batteries that are even more efficient and last for longer, said Dr Galo Paez Fajardo, a material scientist at the University of Warwick, who was involved in the work.
But perhaps we should not be too optimistic about the prospects of batteries that last for days. Demands on them are also likely to rise as phones get more and more sophisticated.
Manufacturers weigh up battery life, size, performance and cost in a complex trade-off – and are likely to continue aiming for a battery that lasts about one day, speculated Professor Jamie Foster, an applied mathematician at the University of Portsmouth.
“If I were a phone designer, I would want to keep the cost as low as possible, give people all the fancy new features that consumer hunger desires while just about giving them a day’s use out of their phone. My guess is they only put in the least amount of battery they can get away with.”
