Why does my phone die in the cold at 30% (or even 50%)?
You're outside on a freezing day, the phone says 35%, you open the camera, and it goes black. Back indoors it turns on again with charge to spare. Nothing is broken: this is how lithium-ion batteries behave in the cold.
What is happening inside the battery
A lithium-ion battery works by lithium ions travelling through a liquid or gel (the electrolyte) from one side to the other. In the cold that liquid gets thicker and the reactions at each side slow down. The result is that the battery fights harder against the current flowing out of it. That fight is called internal resistance, and it costs voltage: the harder the phone pulls, the more the voltage dips while it pulls.
Every phone has a cut-off voltage, a level below which it isn't allowed to run, because running lower could corrupt what it's writing to storage or damage the battery. At room temperature the dip under load is small, so the phone runs almost to 0%. In the cold the dip is large, so a sudden demand can push the voltage under the cut-off while there is still plenty of charge inside. The phone does an emergency shutdown. When it warms up, the resistance falls, the voltage recovers, and it turns back on, often showing much the same percentage as before.
Wirebook has an interactive version where you take a pretend tablet out into the snow and watch the voltage sag. In that simplified model, a game that runs to about 3% at room temperature switches the tablet off at about 49% at -10 °C.
Why it dies when you open the camera
Shutdowns happen at the moment of a power spike, not while the phone sits idle. Common triggers:
- The camera, especially with flash, video or a burst of photos.
- Video calls, navigation with the screen at full brightness, and games.
- Searching for a weak mobile signal on a hill or in the countryside, which makes the radio transmit at higher power.
- Turning the screen on in the dark at full brightness.
That's why a phone can sit happily at 40% in a cold pocket and die the instant you take a photo.
Why the percentage is wrong in the cold
The battery percentage is an estimate made by a small fuel-gauge chip that counts charge in and out and corrects itself using voltage and temperature. A cold, sagging voltage can fool it into thinking the battery is emptier than it is, so the number may fall fast outside and climb back indoors. See why battery percentage jumps or drops suddenly.
Why older phones are worse
Internal resistance also rises as a battery ages, and cold adds on top. A two- or three-year-old phone that is fine indoors may shut down outdoors in winter at 40% or more. On an iPhone, Settings, then Battery, then Battery Health (or Battery Health & Charging) shows the remaining capacity and whether the phone has had unexpected shutdowns. Many Android phones show a battery health or battery information page in Settings or in the manufacturer's support app. A battery replacement usually fixes cold-weather shutdowns that started recently on an old phone.
How to keep a phone going on a cold day
- Carry it in an inside pocket, close to your body. Body heat is the best phone warmer there is. Outer jacket pockets, bag side pockets and bike handlebars get almost as cold as the air.
- Take it out, use it, put it back. A few minutes in the open is fine; an hour clipped to a ski pole is not.
- Turn on Low Power Mode or Battery Saver before you go out. Lower peak power means a smaller voltage dip.
- Download maps for offline use and lower the screen brightness, so the phone isn't working as hard.
- In areas with poor signal, aeroplane mode stops the radio straining (you can still use offline maps and the camera; you won't get calls).
- Bring a power bank, and keep that warm too: it's a lithium-ion battery with exactly the same problem.
- Thick cases help a little by slowing how fast the phone cools, but they can't make heat. They help most if the phone starts warm.
What not to do
- Don't put it on a radiator, near a fire or in front of a car heater vent. Fast heating is hard on the battery and screen, and heat damages batteries more permanently than cold does.
- Don't charge it while it's still frozen. Let it reach room temperature first. See is it bad to charge a phone in the cold.
- Watch for condensation. A very cold phone brought into a warm, humid room can collect moisture. Leaving it in a pocket or bag while it warms up slowly lets it adjust gently.
Does the cold damage the battery?
Using a phone in the cold doesn't cause lasting harm on its own; the lost runtime comes back once it warms up. The two things that do cause lasting harm are charging below freezing, which phones try to block, and heat, especially leaving a phone in a hot car or charging it under a pillow.
Related
Battery percentage jumps or drops suddenly · Is it bad to charge a phone in the cold? · Phone gets hot while charging · Power bank won't charge my phone · Battery health %: when to replace · Phone battery drains overnight · Interactive: chill a pretend tablet and watch it switch off
Questions
Why does my phone turn off in the cold when it still has battery?
Cold raises the battery's internal resistance, so its voltage sags when the phone draws a burst of power. When the voltage drops below the phone's cut-off, it shuts down to protect itself. The charge is still there and comes back when the phone warms up.
Does cold weather drain a phone battery?
Mostly it hides the charge rather than using it up. The battery can't deliver it quickly while cold, so the percentage falls and the phone may switch off, but much of the charge returns once it warms.
What temperature is too cold for an iPhone?
Apple says iPhones are designed for ambient temperatures between 0 and 35 degrees C (32 to 95 degrees F). Below freezing, expect shorter battery life and possible shutdowns, especially with an older battery.
How do I stop my phone dying when skiing or hiking in winter?
Keep it in an inside pocket close to your body, turn on Low Power Mode or Battery Saver, download offline maps, take it out only briefly, and carry a power bank that you also keep warm.
Should I warm my phone on a radiator?
No. Let it warm slowly in a pocket or at room temperature. Fast heating is hard on the battery and screen, and a cold phone brought into a warm room can collect condensation.
Published .