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Michael: So many of the devices we use every day have batteries and it seems like everyone has their own rituals for making them last. Some people store them in the fridge, or unplug as soon as the battery is charged, or even insist on only charging when the battery is on the brink of dying. But when it comes to charging the batteries in things like your phone and laptop, it turns out that many of these strategies don't do very much. And some are actually counter productive.

Batteries work using electrons that try to flow between electrodes. But they're blocked by an electrolyte, which only lets charges flow when the two sides are directly connected by wires. Once all the electrons have reached the positive electrode, the battery is considered discharged, meaning it's out of power. Recharging the battery just involves pushing those electrons back onto the negative electrode to reset the whole process.

All rechargeable batteries lose the ability to hold charge over time as the electrolyte breaks down and the pieces wear out. But what those pieces are made of determines a lot about how to make a battery last as long as possible. A lot of those battery life myths you might hear apply to nickel-cadmium and nickel-metal hydride batteries, the kind you might have in your TV remote. With those, because of the chemical reaction that produces the electrons, it really is better to let them run all the way down before recharging them, and to stop charging pretty much as soon as they're fully charged. Otherwise, crystals can form on the electrolyte and the batteries can break or at least not hold as much charge as they should.

But most portable devices these days, like your phone and your laptop, use lithium-ion batteries which work differently. Lithium-ion batteries do get damaged if they're overcharged, but the batteries and chargers are usually designed to stop charging before that happens. So you don't have to worry about unplugging your phone or laptop as soon as it's charged.

And waiting until lithium-ion batteries are close to dead before charging them can actually make their lives up to 5 times shorter than always charging before they dip below 70%. The higher the charge before you plug in, the longer the battery will last. With that said, if you have something that tells you how much time you have left on your battery, not just the percentage, you should fully discharge it about once a month to help the computer recalibrate its estimate.

But the biggest thing that affects all batteries is temperature. Electrochemical reactions happen faster when it's hotter. So batteries do break down faster in prolonged heat. But that doesn't mean you should store your batteries in the freezer. The air in the freezer, or in the bag with batteries in it you put in the freezer has plenty of water vapor just waiting for a place to crystallize into ice. And you really, really don't want wet, icy batteries. So if you want your phone and laptop batteries to last, keep them plugged in as much as possible. And no matter what kinds of batteries you're storing, they'll be just fine if you stick them in a drawer.

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