Millions of people could be unwittingly reducing the lifespan of their phone battery as temperatures continue to climb, yet specialists say that one straightforward adjustment during the heatwave could help preserve its health considerably.
Another record was broken on Thursday when the UK recorded 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 again in 2020.
With much of the UK expected to enjoy sustained hot weather this weekend, experts have cautioned that one widespread habit can inflict lasting harm on lithium-ion batteries, diminishing how long they retain their charge over time.
This follows Vodafone research revealing that one in four people consider the fear of their phone losing power 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 that leaving your handset on a sun lounger, car dashboard or table in direct sunlight could significantly shorten its battery lifespan. Experts instead advise keeping it tucked in a pocket, bag or shaded spot wherever possible.
Scientists explain that 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 Habits Matter
Charging a device in temperatures ranging from 35C to 45C can also inflict additional wear, while a battery kept at 40C and fully charged could lose around 35% of its capacity within a single year.
Consequently, experts have advised making one straightforward adjustment to extend your phone's lifespan — 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.
Many newer handsets incorporate 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."
Modern Batteries and Best Practices
Nevertheless, Paez Fajardo noted that contemporary batteries have advanced considerably, suggesting it's generally preferable to depend on your phone's integrated charging features rather than manually disconnecting it.
Experts also refuted the outdated notion that batteries ought to be regularly depleted 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."
While fast charging remains convenient, it should be employed with caution, particularly during warmer conditions, as it produces additional heat. When purchasing a new charger, Speight advises selecting one compatible with USB Power Delivery (USB PD), which regulates charging more effectively and minimises unnecessary strain on the battery.
