Why Extreme Temperatures Mess With Your Batteries

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You probably don't even think about the battery in your phone, or your car, or your flashlight — until it stops working. Often, that's when you're getting around the campground in the peak of summer or snapping a snow-angel selfie in the dead of winter. Why are batteries so sensitive to harsh weather? It's because inside each battery is a tiny chemical reaction, and chemical reactions are very dependent on temperature.

A Science Lab in Your Flashlight

Nearly every battery, from the ones inside your flashlight to the one that starts your car, is made up of three basic parts: two electrodes, an electrolyte, and a separator. The two electrodes are designed for each end of the battery: The cathode connects to the positive end, the anode to the negative. The electrolyte that sits between them is usually a liquid-like substance that contains electrically charged particles called ions. The separator does just that: It separates the cathode from the anode, keeping them from coming into contact and short-circuiting.

When you put batteries in a flashlight, you're completing a circuit. That is, you're making it so the chemical energy in the electrolyte can convert to electrical energy, travel out of the cathode and into the light bulb, and return in a closed loop into the anode. That conversion into electrical energy happens via a chemical reaction that takes place between the atoms in the electrodes and the ions in the electrolyte.

You're Hot Then You're Cold, You're Yes Then You're No

There's a particular rule in chemistry called the Arrhenius equation, which says that the higher the temperature, the faster a chemical reaction will take place. So when you take your phone out into the blazing heat of a summer hike, the chemical reactions inside the battery go into overdrive. The result? You look down at your phone, and your battery icon is in the red.

Likewise, the colder the temperature, the slower the chemical reaction. If you're taking a digital camera out to shoot pictures of the new snow, you might find that your battery life is strangely short. That's because the sluggish chemical reaction makes the batteries produce less and less current until they can't keep up with the camera's demand. Luckily, once the batteries are warm again, they'll power devices just fine. That slow discharge rate in the cold is also the reason some people store batteries in the fridge or freezer, incidentally, although that's not strictly necessary. According to Duracell, you just need to keep batteries in a dry place at normal room temperature to ensure they live a long, strong life.

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For more explanations of the things you encounter every day, check out xkcd creator Randall Munroe's wildly popular "Thing Explainer: Complicated Stuff in Simple Words." We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Related: Easy Way to Tell Whether a Battery Is Dead

Written by Ashley Hamer June 15, 2017
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