Why your phone dies in the cold with battery left, and how to stop it

Why it switches off at 30 percent

The percentage on the screen is an estimate of the energy left in the battery. What fails in the cold is something else: how much power the battery can hand over at a given moment. Apple's page on iPhone battery and performance says a battery's impedance temporarily increases at a low state of charge and in a cold environment, and that a battery with high impedance might not be able to provide enough power to the system. When that happens, the phone performs a shutdown to preserve its electronic components.

Apple lists three things that make those unexpected shutdowns more likely: a low state of charge, a higher chemical age, meaning an older battery, and colder temperatures. The three add up. A two-year-old phone at 25% on a frozen tram stop has all of them at once, which is why it can go black while a newer phone at 70% next to it keeps working. Apple adds that the changes caused by low charge and cold are temporary.

What Apple, Google and Samsung say about cold

• Apple: iPhone and iPad are designed for ambient temperatures between 0 and 35 °C. Below that, battery life can temporarily shorten, the device can turn off, and it might not charge or could stop charging.
• Google: if a Pixel's temperature is below 0 °C, it may shut down suddenly. On a Pixel 6a or later, Settings, Battery, Battery diagnostics, Phone is very warm shows a Cold state when the phone has been out in the cold.
• Samsung: the optimal usage temperature for a Galaxy is 0 to 35 °C, and extended use or storage below 0 °C may lead to unexpected shutdowns and shorter battery life.

The three agree on the important part. Apple says battery life returns to normal once the device is back at higher temperatures, and Samsung says to let the device adjust to the optimal usage temperature after exposure to extremes. Cold costs you the afternoon, not the battery.

A day on foot in a winter city

• Carry the phone in an inside pocket, against your body, not in a bag or the outer pocket of a coat.
• Take it out, do what you need, and put it back. A phone that spends an hour in your hand in the open is the one that switches off.
• Plan the route indoors, at breakfast or in a café, and download the area as an offline map so the phone is not working through every street.
• Turn on Low Power Mode or Battery Saver in the morning, not when the battery is already low.
• Keep the power bank in an inside pocket too, and top up at lunch rather than waiting for the warning.

The last point matters more in winter than in summer, because Apple names a low state of charge as one of the triggers. In Oslo, Helsinki or Reykjavik in January, a phone kept above half is much less likely to go black on you than one you let run down. How to download maps is in our offline maps guide, and the power modes are explained in why your phone drains faster when travelling.

Tickets, bookings and the address of the hotel

In a cold city, the phone often holds things you cannot afford to lose at a bus stop: the transport ticket, the museum booking, the hotel address in the local language. If it shuts down, all of that goes with it until it warms up, and that can take a while outdoors.

Keep a backup that does not need a battery. Write the hotel address on paper, carry a physical bank card that works contactless, and screenshot or print anything you need at a gate. On iPhone, Express Mode transit cards have a power reserve that Apple says can keep some cards working for up to five hours when the iPhone needs charging, but not if the phone is switched off, so do not count on it after a cold shutdown. Our guide to transport tickets on your phone goes through the options.

When it has already switched off

Do not keep pressing the power button in the street. Put the phone inside your clothes or take it indoors and give it time. Google's advice for a cold Pixel is to let the phone warm up gradually, so no radiators, hair dryers or hand warmers pressed against it.

Charge it once it is warm, not before. Apple says an iPhone that is too cold might not charge or could stop charging, and shows a Charging On Hold notice that charging will resume when it returns to normal temperature. Samsung likewise limits charging when the temperature is outside a certain range. Once the phone is warm again, Apple says battery life returns to normal.

Nothing on the phone is lost in the process. Your lines, including a travel eSIM, stay installed and reconnect to the network once the phone is back on.

Nights in a car, a cabin or an unheated room

Apple gives a separate range for storing a device: between -20 and 45 °C. Samsung is blunter and says not to place or store a phone in cold environments, like below-zero temperatures during winter. A rental car parked overnight in Lapland or in the north of Iceland can go well below that, and so can a cabin before the heating is on.

So the phone, the power bank and any spare devices come inside with you at night, even if you plan to use them in the car the next morning. If you use the phone as a navigator, keep it in your pocket while the car warms up and mount it afterwards. Our article on using your phone on a ski trip covers the mountain side of winter: slopes, borders between countries and emergency numbers.

If it happens every winter, check the battery

Some phones die in the cold far more easily than others, and age is the usual difference. On an iPhone, open Settings, Battery, Battery Health to see the maximum capacity, and Apple shows a message when the battery's health is significantly degraded. Samsung lists a phone that turns off unexpectedly in cold environments or during winter as a sign the battery may be wearing out, and its Samsung Members app runs a phone diagnostic that rates the battery as Normal, Weak or Bad.

A battery replacement before a winter trip is cheaper than a phone that keeps switching off in the street. If you are going north, check this at home, along with the rest of your setup: for data, a country pack such as Norway or Finland from Snoozim is installed before you leave and starts counting when it first connects there.