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  • Batteries don't do so hot when it's cold.

  • If you live in a cooler climate, you may have noticed this in the form of your car refusing to start on a chilly morning,

  • or your battery level plummeting on your phone as you stand on the train platform in the freezing cold.

  • But it's not the batteries' fault exactly.

  • It's not that technology works worse in the cold.

  • It's chemistry.

  • And that's a much harder problem to fix.

  • Batteries aren't just big buckets of negatively charged electrons,

  • even though that's what moves through the wire when you plug a battery into something.

  • The electrons start as part of neutral atoms or molecules, and they're released by a chemical reaction inside the battery.

  • As a result of the reaction, the electrons move through a wire and meet up with positively charged molecules on the other side of the battery.

  • That movement creates a current that powers your stuff.

  • The exact chemistry depends on the type of battery, but that's the general idea for all of them.

  • And it's also where temperature comes in.

  • Temperature is a measure of heat.

  • And at a molecular level, heat is movement.

  • It's particles jiggling around.

  • Higher temperatures mean more molecular movement and more molecules bumping into each other,

  • which makes chemical reactions more likely.

  • So, in general, when the temperature drops, chemical reactions slow down.

  • But how much depends on what's reacting.

  • Which helps explain why you might notice some batteries suffering more than others in winter.

  • Not all batteries are made from the same stuff.

  • Traditional alkaline batteries, for instance, like many non-rechargeable AAs, AAAs, and the like, contain a solution of water and potassium hydroxide.

  • That watery solution can freeze at really low temperatures,

  • but it starts losing its chemical punch well before it actually turns to ice.

  • So don't try to use your TV remote outdoors in a blizzard.

  • That's our advice for you.

  • Then there are lithium-ion batteries like the one in your phone.

  • They tend to beat alkalines in cold weather, but even they have their limits,

  • something that's been holding back electric cars in areas that get really cold.

  • A phone battery's cold-weather performance actually tricks the phone into thinking it's dead.

  • The difference between a charged, cold battery and a dead battery is that the charged battery

  • still has the capacity to produce enough electrons to theoretically power your phone.

  • But because the temperature slows down those reactions, the electrons are released too gradually to do any good.

  • Your phone doesn't have a thermometer, meaning it doesn't know how cold it is.

  • So it just assumes there's nothing left in the battery to react -- which is what happens when the battery's dead.

  • So the phone tells you the battery is low, when really it's just cold.

  • Warm the battery up, so that more reactions can happen again, and the phone will realize it still has more juice.

  • One other very common battery is the lead-acid battery, widely used in cars.

  • Cold slows that reaction, too -- but it also makes oil and other components of the engine harder to move.

  • Sp that's double trouble for you, making some cars particularly hard to start on cold mornings.

  • So be nice to your batteries this winter.

  • If your phone dies on you, just hold it against your body like a little baby duck.

  • Thanks for watching this episode of SciShow, and thanks to our patrons for making it and everything we do possible.

  • You guys are awesome, and you're helping make free stuff for the whole world to enjoy.

  • If you're interested in joining this community of awesome humans, check out patreon.com/scishow.

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