How heat and cold affect your phone (and how to protect it)

What heat does to your phone

Phone batteries are lithium-ion, and they age faster when they're hot. Every battery loses some capacity over time, but heat speeds that up, and the damage doesn't reverse when the phone cools down.

When a phone gets too hot, it protects itself. You may notice:

• charging slows down or pauses
• the screen dims
• the camera flash or some features stop working
• a temperature warning appears until it cools down

What cold does to your phone

In freezing weather, a battery can't deliver power as well, so the percentage may drop quickly or the phone may switch off. This is usually temporary: once the phone warms up, normal battery life returns.

How to protect your phone

• Never leave it in a parked car on a warm day

  The inside of a car can get far hotter than the air outside.

• Keep it out of direct sun,

  Including on windowsills, dashboards and sun loungers.

• Take it out of a thick case while charging

  If it gets hot. Some cases trap heat.

• Don't charge it under a pillow or duvet

  Charge it on a hard surface with air around it.

• Let it warm up gradually in winter

  Keep it in an inside pocket when you're outdoors, and avoid putting a very cold phone straight onto a radiator.

• Avoid heavy gaming or video calls in the heat

  They make the phone work harder and get hotter.

Look after the battery as it ages

• On iPhone, Optimised Battery Charging learns your routine and waits to finish charging past 80% until you need it, which reduces battery ageing. Find it under Settings > Battery > Battery Health & Charging.
• Many Android phones have a similar "adaptive" or "protect battery" option under Settings > Battery.
• You don't need to let the battery run down to zero. Topping up whenever it suits you is fine.

Things to be careful about

• If your phone gets very hot while charging, or the battery looks swollen, unplug it and stop using it.

• Use a good-quality charger and cable. Cheap, unbranded chargers can overheat.