Why Your Phone Dies in the Cold (and How to Protect It in an Ottawa Winter)

Every winter, the same thing happens to thousands of phones in Ottawa: you step out at the bus stop, open your maps app, and the phone dies at 30%. It's not your imagination, and it's usually not a broken phone. Ottawa is one of the coldest capital cities in the world, and phone batteries were never designed for its winters.

Why the cold drains your battery

A lithium-ion battery makes power through chemical reactions. In the cold those reactions slow down, so the battery can't deliver current as easily. When the phone asks for a burst of power, for the camera, GPS or a weak cell signal, the voltage dips. If it dips far enough, the phone shuts itself off to protect its components, even though the battery still holds charge.

That's why a phone that died outside often comes back to life indoors, sometimes showing more battery than when it shut off.

What Apple says about temperature

Apple's temperature guidance is clear:

• iPhone and iPad are "designed for use where the ambient temperature is between 0° and 35° C."
• Store them between −20° and 45° C, and don't leave them in a car.
• Very cold conditions "might temporarily shorten battery life and could cause your device to turn off. Battery life will return to normal when you bring your device back to higher ambient temperatures."
• "If your iOS or iPadOS device gets too cold, it might not charge or could stop charging."

Android phones use the same battery chemistry, so the same rules apply.

Why some phones cope worse than others

A worn battery has less headroom, so it hits the shutdown point sooner. If your phone shuts off in the cold every day, or even in a cool room, the battery is probably past its best. Check Settings › Battery › Battery Health on an iPhone; below 80% means it's time. Our battery replacement guide explains the numbers.

8 ways to protect your phone this winter

1. Carry it in an inside pocket. Your body heat is the best phone warmer there is.
2. Use it less outside on bitter days. Check directions before you leave, and use earbuds or voice commands rather than taking the phone out.
3. Leave home with a full charge, and keep a power bank in a warm pocket.
4. Don't charge it while it's frozen. Let it warm to room temperature first; Apple says a cold phone might not charge.
5. Don't speed up warming with heat. No radiators, hair dryers or car vents; heat is what permanently damages batteries.
6. Let it warm gradually when you come in. Leave it in your pocket or bag for a few minutes so moisture doesn't condense on a very cold phone.
7. Don't leave it in the car overnight. Ottawa nights can drop below Apple's −20 °C storage limit.
8. Keep a case on. It won't keep the phone warm, but icy sidewalks are where a lot of our winter screen repairs start.

Snow, slush and road salt

Melting snow and salty slush are harder on phones than cold air. Salt water is corrosive, especially inside the charging port. If your phone gets wet, dry it off, don't charge it until the port is dry, and follow our water damage steps. If it stops charging after a slushy walk, see why your phone won't charge.

When to get it checked

Bring your phone in if it shuts down in the cold at 30% or more, dies indoors at normal temperatures, won't charge after warming up, or shows any sign of swelling (see our swollen battery guide). Battery checks at our shop at 572 Bronson Avenue are free, and most replacements take under an hour.