Millions of people could be unwittingly cutting short the lifespan of their phone battery as temperatures climb, but specialists say one straightforward adjustment during the heatwave could help preserve it for longer.
Record-Breaking Heat
Yet another record fell on Thursday when the UK logged its eighth day at or above 34C in a calendar year, surpassing the previous record of seven days set during the summer of 1976 and in 2020. With large swathes of the UK set to enjoy continued hot weather this weekend, experts have cautioned that one widespread habit can cause lasting damage to lithium-ion batteries, diminishing how long they retain their charge over time.
This follows Vodafone research which revealed that one in four people consider the fear of their phone running out of battery to be the most stressful part of their day.
Heat is the Enemy
"Basically, the worst enemy a battery can have is heat," Galo Paez Fajardo, a research assistant professor at the University of Warwick, told The i. He went on to explain that when a phone heats up, "those are signs that your device is telling you: 'Stop, cool it down', because when heat gets in is when the batteries accelerate the degradation."
This means leaving your handset on a sun lounger, car dashboard or table in direct sunlight could reduce its battery lifespan. Experts instead advise keeping it tucked in a pocket, bag or shaded spot wherever possible.
Scientific Impact of Temperature
Scientists say the chemical reactions within lithium-ion batteries accelerate as temperatures climb. Every 10C rise above approximately 25C can roughly double the speed at which batteries deteriorate. Charging a phone in temperatures between 35C and 45C can also cause additional wear, while a battery kept at 40C and fully charged could lose around 35% of its capacity in merely a year.
Consequently, experts have advised making one straightforward adjustment to help your phone last longer — avoid leaving your battery at 100% charge during hot weather.
"You don't want to be sitting at high states of charge at high temperatures," said David Howey, professor of engineering science at the University of Oxford.
Smart Charging Features
Many newer phones feature intelligent charging capabilities that halt charging at approximately 80% before completing the charge nearer to the time you typically disconnect the device. Billy Wu, director of research at Imperial College London's Dyson School of Design Engineering, said: "Normally we say about 80 per cent charge is a good number to reach and doesn't accelerate the degradation too much."
Nevertheless, Paez Fajardo said modern batteries have advanced considerably, meaning it's frequently best to depend on your phone's integrated charging features rather than manually disconnecting it.
Myths About Draining Batteries
Experts also rejected the outdated notion that batteries should routinely be drained entirely before recharging. "Having your phone at zero per cent and 100 per cent are both high-stress states for your battery," said Adam Speight, senior researcher for product testing at Which? Paez Fajardo added: "Now, current batteries are fine if you charge them at any percentage. Going all the way down to zero per cent is actually detrimental for some chemistries."
Fast Charging and Charger Choice
Rapid charging remains helpful but ought to be employed with caution, particularly in warm weather, as it produces additional heat. When purchasing a new charger, Speight suggests selecting one that supports USB Power Delivery (USB PD), which handles charging more effectively and minimises unnecessary strain on the battery.
