Why do cold batteries lose their charge? Cold batteries don’t lose their charge exactly. In colder weather, the atoms that are inside the batteries can’t move as much and that means they can’t produce as much power.
You may have noticed that if you use your phone on a particularly cold day, it runs out of power and shuts down even though the battery reading still says 60%. This is a problem with all batteries, not just the ones that are in phones. It is one reason why electric planes will be difficult and why electric cars have limitations. Electric planes would have a problem because it gets very cold at the height planes fly at, and their batteries would lose their power pretty quickly. The problem with electric cars is that they are fine in hot places, but if you own an electric car in a country that gets very cold, you are going to get much worse mileage in the winter than you will in the summer. If you are driving your electric car in a cold country, the engine will need to produce extra heat to keep the battery warm, which can impact the distance you can drive. Electric cars are much more efficient than combustion engine cars, and they don’t produce much heat. A combustion engine produces a lot of heat, which is actually a waste product, and this heat can be used to heat the car. Electric cars have to have an extra electric heater, which takes away some power that the car could use to drive.
All batteries perform badly in cold conditions, but some perform less badly than others. Batteries produce electricity because of chemical reactions. Let’s look at lithium-ion batteries, which are the most common at the moment and are the ones you have in your phone. Lithium-ion have become the most common because they are light, charge very quickly, and last longer than other types of batteries. Lithium-ion batteries are currently quite a problem for the environment because of the way a lot of the lithium is mined and they way they are disposed of, but we are not looking at that today.
Lithium-ion batteries work by stripping electrons from lithium atoms and sending those electrons to power whatever device you are using. The lithium-ion battery has a cathode and an anode that are divided by a barrier. When you charge the battery, the lithium ions have a positive charge and they settle by the anode. When you need power, the lithium ions are carried through the barrier by the electrolyte, but the electrons cannot pass through and they are stripped off, heading to the anode. The lithium ions with no electrons settle by the cathode. The electrons are sent to the cathode via a wire, and that is where the electric current comes from. When you charge the battery, the process is reversed. The lithium ions head back through the barrier to the anode and electrons from your power source are sent via the wire to the anode, where they join up with the lithium ions.
So what happens in cold weather? The exact same chemical process happens, but it happens much much more slowly. Heat is just energy and when atoms have energy they move a lot more. As the temperature comes down and the amount of thermal energy dissipates, atoms move a lot less. That is why ice, the solid form of water, hardly moves while steam, the gaseous form of water, moves all over the place. You might have charged your battery to 100% in the house the night before, but once you get to the ski slopes and the temperature plummets, those lithium atoms with the electrons don’t have enough energy to move away from the anode and cross the barrier. They just sit there, holding onto their electrons. Your phone doesn’t know that. All your phone knows is that almost no electricity is being passed along the wire, so it shuts down. Often, if this happens, you can put your phone inside your clothes for a few minutes to warm it up enough for some of the lithium atoms to start moving. That might give you a little more time with your phone. As I said earlier, electric cars get around this problem by heating the batteries themselves. As long as they have enough power to start the engine, they can warm up their own batteries and keep the power coming. And this is what I learned today.
Try these:
Sources
https://citylabs.net/temperature-control/cold-batteries
https://physics.stackexchange.com/questions/762471/how-do-batteries-lose-capacity-in-winter
https://www.apple.com/batteries/why-lithium-ion
https://www.energy.gov/energysaver/articles/how-lithium-ion-batteries-work
Photo by Flo Maderebner: https://www.pexels.com/photo/two-man-hiking-on-snow-mountain-869258/