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Polar Battery Vortex

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If you’ve noticed your device batteries taking a nosedive these past several weeks and you live in the Northeast or Midwest of the United States, you aren’t alone.

Modern mobile electronic gizmos are powered by lithium-based batteries that don’t like the cold any more than you do. Lithium-based batteries become far less efficient when it starts to get cold because the power they generate is based off of a a chemical reaction taking place inside the battery. When it gets cold, that reaction can’t happen as efficiently.

To compound the problem, your device probably has some software built in that tells it to shut down if the battery is under-volting, meaning if the phone it needs 3.7 volts to run and the battery only is capable of 2.9, the phone will shut off thinking the battery is near dead. There’s a good reason for this though. even when the phone is off, it needs a small amount of power to tell you it needs to be plugged in.

What can be done? Well, keep the phone warm. Put it in a pocket thats next to your body and don’t pull it out for extended periods. If your car looks like that Lake Michigan lighthouse, maybe even consider putting one of those chemical hand warmers in the pocket where your phone is. Or better yet, stop trying to take selfies on the frozen tundra.

*Nerd Note:

If you must know what’s really going on in your battery, here’s a semi-technical explanation that won’t give you high school physics nightmares:

Your phone likely operates at a near constant voltage. The size of the battery and what the phone is being asked to do determines how much power the phone will draw (Amps).

Lots of people find it useful to think of electricity like water to visualize whats going on. Think of the volts as the diameter of the hose, your demand on the phone (downloading a huge file versus standby) as how much you are opening up the spigot (Amps), and the size of the battery as how big the water tank is (Amp-hours — or for little batteries like in the iPhone, milliAmp-hours “mAh” ).

Imagine that when your battery starts to get too cold, some percentage of the water in your storage tank has frozen over and can’t be drawn through the hose and into your phone until it thaws out.

The chart is pulled from data released in a Sony internal training manual, meant to teach employees about the specific properties of their lithium batteries. I chose Sony because there’s a good chance your iPhone is using a Sony battery. The chart isn’t exact (if you must know, it’s based on a best-fit function built off of some discrete data points, not from a Sony-supplied function).

Here are some more quick charts clipped from the manual if you are interested:

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Expected operating life of a smaller Sony lithium battery with the same technology as iPhone batteries.

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Slightly more specific power discharge characteristics of a battery inside a GSM phone.

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Apple’s own recommendation for iPhone usage temps. They clearly understand the issue, and suggest that you just not try to use your phone at all if temps. drop below freezing.