Across the UK, millions of people take their phones to bed and plug them into a wall socket to charge overnight.
And, as it turns out, those people are all making a big mistake.
A growing body of evidence suggests charging smartphones to 100 per cent – and then leaving them on charge for several unnecessary hours – shortens battery lifespan.
In fact, it’s why many devices start struggling to ‘hold a charge’ by the time they’re a year old.
And since few modern handsets have modular batteries, incorrect charging techniques could force you to upgrade your device prematurely, as battery life dwindles from days to hours.
(That’s to say nothing of the environmental impact of consigning a non-recyclable phone full of harmful chemicals to the dustbin earlier than would otherwise have been necessary.)
Yet many of us worry constantly about our phones having insufficient charge to complete essential tasks.
Nomophobia (fear of being without a phone) is becoming commonplace.
So why is our nightly routine so detrimental? And how should we approach the challenge of ensuring there’s enough power left on our phones to last throughout the day?
The risks of overnight charging
Replenishing smartphones involves adding electrical power into the lithium-ion cells within their rechargeable batteries.
Regularly subjecting it to eight hours of charging triggers a process called plating, where lithium ions become deposited as a metal within the battery.
That in turn reduces the battery’s stability. Plus, trying to charge it ‘beyond’ 100 per cent stresses it, and generates excess heat that could also have a detrimental effect.
The most obvious consequence from a user’s perspective is reduced battery life – increasing the temptation to leave the phone on charge overnight and thereby exacerbate the damage.
Dos and don’ts
These are the optimal ways of charging smartphones, plus a few things worth avoiding if at all possible:
Do partially charge your phone. Voltages vary at different charge levels, and charging your phone between 30 and 80 per cent has been proven to prolong its lifespan.
Don’t fully discharge the battery. Forcing the device to run out of power before recharging it hasn’t been necessary since we moved away from lead-acid batteries.
Do keep a charger with you at all times. As partial top-ups are better for battery lifespan than full ones, ensure you have charging facilities at home and at work.
Don’t play games or watch videos while charging. Parasitic loads (where part of the battery constantly charges and drains) generate heat, ruining specific battery cells.
Do turn your phone off as it charges. Where possible, evidence suggests processor and screen-intensive activities shouldn’t be undertaken on mains power.
Don’t expose the phone to high temperatures. Battery life is lessened by ambient temperature, so recharge the phone in a cool environment out from direct sunlight.
Do use fast charging sparingly. High-speed power cables aren’t meant for daily use. They’re fine for occasional top-ups, but slower charging is always preferable.
Don’t constantly charge to 100 per cent. Experts agree that a zero to 100 per cent charge once a month is optimal, but it becomes counter-productive more frequently.
Do remove protective cases while charging. As mentioned above, heat is the enemy of phone batteries. Removing plastic or rubber covers keeps the handset cooler.
Don’t buy cheap third-party chargers. There have been reports of phones catching fire while using non-approved third-party chargers sourced cheaply online.