Charging Your Phone in Cold Weather: What Actually Hurts

Cold weather does not permanently damage your phone's battery. Charging a battery that has dropped below freezing does, and a winter evening outdoors sets you up for exactly that. Apple designs iPhone and iPad for ambient temperatures between 0 and 35 degrees C, and Battery University's charging guidance is blunter: "no charging is permitted at freezing temperatures because of the reduced diffusion rates on the anode."

So the phone that quits at a Christmas market has not been harmed. The phone you plug in while it is still cold from your pocket might be.

What the cold actually does, and why it reverses

A cold lithium-ion cell has not lost capacity. It has lost access to it. Battery University's discharge data puts a number on the gap: "A battery that provides 100 percent capacity at 27°C (80°F) will typically deliver only 50 percent at -18°C (0°F)," and at -20°C "most batteries are at about 50 percent performance level."

That halving is not damage. The same page says the reduced capacity "only applies while the cell is in that condition and will recover in room temperature."

Apple describes the same effect from the user's side. Using a device in very cold conditions outside its operating range "might temporarily shorten battery life and could cause your device to turn off," and "battery life will return to normal when you bring your device back to higher ambient temperatures." Apple's own comfort zone is narrower than the operating range: 16 to 22 degrees C is what it calls ideal.

This is why a phone sitting at 40 percent can shut off at a bus stop and then show something close to 35 percent indoors twenty minutes later. Nothing was lost in between. The cell could not push current fast enough at that temperature, the phone read the voltage sag as an empty battery, and it shut down rather than crash mid-task. The same voltage-versus-capacity gap explains why a power bank charges a phone more slowly than its rating suggests.

Charging a frozen battery is the part that does not reverse

Battery University sets the usable charging window at 5°C to 45°C (41 to 113°F) for a fast charge. Below 5 degrees the current has to come down. Below zero it has to stop, and the reason is physical rather than cautious: "Plating of metallic lithium occurs on the anode during a sub-freezing charge that leads to a permanent degradation in performance and safety." Cells that have been plated are also "more vulnerable to failure if exposed to vibration or other stressful conditions."

Charging very slowly is not a way around it. At -30°C the allowable charge rate works out to 0.02C, which would stretch a full charge "to over 50 hours, a time that is deemed impractical."

Heat works the other way round. There, the ambient temperature itself is the problem: Apple warns against ambient temperatures above 35 degrees C because they "can permanently damage battery capacity," which is the subject of what Apple actually says about iPhone overheating in the sun. Cold is safe to stand around in. It is the charging that bites.

A phone that refuses to charge is the safeguard working

Apple states it plainly: "If an iOS or iPadOS device gets too cold, it might not charge or could stop charging." Samsung's battery guidance says the same thing in different words. Temporary exposure to extreme temperatures "will activate the device's safeguards," and "charging will be limited to protect the battery if the temperature goes outside of a certain range."

A "Charging stopped" notice on a Galaxy that has been standing outside in January is therefore not a fault to troubleshoot. It is what sits between a cold cell and lithium plating. Swapping the cable or trying a different socket changes nothing, because the block is a temperature reading rather than a power problem.

Temperature by temperature

What to do at a winter market, a ski lift or an outdoor match

1. Warm the phone before you plug it in. Samsung's instruction is direct: if you expose the device to temperature extremes, "let the device adjust to the optimal usage temperature (32° - 95°F) before use." Five minutes inside a jacket beats plugging in straight away.
2. Inner pocket, not outer pocket. A phone against your body sits far closer to Apple's 16 to 22 degree comfort zone than one in a shell pocket or a backpack, which track the air temperature.
3. Charge where you are warm, not where the phone is cold. A bar, a heated tent, a train carriage. Charging outdoors at sub-zero temperatures is the one thing on this list with a permanent cost.
4. Do not leave it in the car overnight. Apple's storage floor is -20 degrees C, and a parked car in a Nordic cold snap goes under it. The same applies to a powerbank left in a glovebox, which is covered in how to store a power bank so it stays ready.
5. Treat the percentage as pessimistic. A phone that shuts down at 20 percent in the cold has not used that charge. It will come back indoors.

One practical note if you are out all day and already low. A rented powerbank has an advantage in winter that has nothing to do with its capacity: it travels in the same inner pocket as the phone, so the pair charge near body temperature instead of at the air temperature. Brick's stations sit inside venues like hotels, restaurants and transport hubs, so the powerbank you take out starts at room temperature rather than needing to be warmed up first, and it goes back to any station on the network. How power bank sharing works covers the rent-and-return side.

Frequently asked questions

Does cold weather permanently damage my phone battery?

Not on its own. Battery University states that reduced capacity at low temperature "only applies while the cell is in that condition and will recover in room temperature," and Apple says battery life "will return to normal" once the device warms up. The permanent damage comes from charging a battery that is below freezing, which plates metallic lithium onto the anode.

Why does my phone say charging stopped when it is cold?

Because the phone is protecting the cell. Apple says a device that gets too cold "might not charge or could stop charging," and Samsung says charging "will be limited to protect the battery if the temperature goes outside of a certain range." Warm the phone to room temperature and charging resumes.

How much battery do you actually lose in the cold?

Roughly half at around -18 to -20°C. Battery University's figure is that a battery delivering 100 percent capacity at 27°C typically delivers only 50 percent at -18°C. The charge is not gone, only unavailable at that temperature.

Can I charge a powerbank in cold weather?

A powerbank holds the same lithium-ion chemistry as the phone, so the same 5 to 45°C fast-charge window and the same sub-freezing plating risk apply. Bring it indoors or inside a jacket before recharging it.

Is it safe to use my phone in freezing weather, just not charge it?

Using it is the lower-risk half. Apple's stated operating range starts at 0°C and warns only that very cold conditions "might temporarily shorten battery life and could cause your device to turn off." Charging below freezing is the part that carries permanent degradation.

The one rule worth carrying into winter

Warm first, charge second. Everything else the cold does to a phone battery undoes itself the moment the phone is back at room temperature, and a percentage that dropped outdoors is a reading rather than a loss. The single irreversible move is pushing current into a cell that is sitting below zero, and both Apple and Samsung have already built the block that stops you. Let it.