For an object that barely ever leaves our palms, the smartphone can sometimes feel like an arcane piece of wizardry. And nowhere is this more pronounced than when it comes to the fickle battery, which will drop 20 per cent charge quicker than you can toggle Bluetooth off and give up the ghost entirely after a couple of years of charging.
To make up for these inadequacies, we’ve made all kinds of battery myths. Whether it’s avoiding leaving your phone on charge overnight, or powering off to give the battery a little break, we’re forever looking for ways to eke out a little more performance from our overworked batteries, even if the method doesn’t make an awful lot of sense.
To help sort the science from the folklore, we asked a battery expert to give their verdict on some of the most pervasive myths, explain the science behind the rumours and, just maybe, offer us some sage advice on extending the life of our smartphones.
Even when your battery is at 100 per cent, there’s still room for some more charge
There is more juice in your smartphone battery than the percentage displayed suggests, but if you used that juice you’d end up dramatically reducing the overall lifespan of the battery. At the crux of this problem is a delicate trade-off played by manufacturers. Increasing the available charge within a battery reduces the number of times that battery can be charged and discharged without being damaged internally. To make batteries last for hundreds or thousands of charge cycles, manufacturers place limits on the amount of juice that batteries can discharge.
To understand why, you need to know a little about how batteries work. The guts of most lithium-ion batteries, like the ones in smartphones, laptops and electric cars, are made of two layers: one made of lithium cobalt oxide and the other of graphite. Energy is released when lithium ions move from the graphite layer to the lithium cobalt oxide layer. When you charge up a battery, you’re simply shifting those lithium ions back the other way – out of the lithium cobalt oxide layer and back to the graphite.
This is where we get to the problem with battery life and charge cycles. Shift too many of those lithium ions out of the lithium cobalt oxide layer, and the whole structure of the layer messes up. “The atomic structure of the material actually falls apart if you remove all that lithium,” says Kent Griffith, a researcher on energy storage at University of Cambridge.
So while it is possible to charge a battery beyond 100 per cent, the only way to do that is to pull out more of those crucial lithium ions. “It'd be like pulling all of the supports out of the floor of a building,” Griffith says. You could get the lithium ions out, but good luck putting them back once you’ve messed up that internal structure.
That’s why manufacturers set limits on the amount of charge in their batteries. Most of the time, they’re set so only around half of the lithium in the lithium cobalt oxide layer is removed during one full charge. “Your battery could give you more charge if you went beyond removing half of the lithium, but you wouldn't be able to do that very many times.”
Charging your phone on airplane mode makes it charge faster
True (kind of)
A common tip to speed up phone charging when you’re in a hurry is to stick it on airplane mode. Airplane mode means that all the radio frequencies are turned off, so you won’t have any cellular data and – with some phones – your Bluetooth and Wi-Fi connections will also be severed. In theory, since your phone is doing less work, the battery should charge faster, right? That’s technically true but the speed difference turns out to be pretty minimal. A trial by CNET in 2014 found that turning on airplane mode only shortened the charging time by four minutes. Maybe being unable to tweet while you wait isn’t all that worth it.
Having Wi-Fi and Bluetooth on in the background is a big drain on battery life
Apart from the screen, one of the biggest drains on battery life is the energy your phone wastes trying to find and connect to Wi-Fi or data networks. If you’ve ever noticed your battery plummeting while on a train, it’s probably because your device is working overtime to connect to a mobile network. “If you can connect to something stable, like if there’s WiFi on the train, it’s probably better to connect to that,” Griffith says. Reducing screen brightness and the time it takes your phone to go to sleep are also easy ways to extend your battery life.
Using an unofficial charger damages your phone
Not all phone chargers are created equal, and that could have a damaging effect on your phone’s battery life. Chargers have all sorts of controls that limit the amount of current delivered and stop it charging when the battery is full, but some off-brand chargers might not have such rigorous safety settings.