Should You Let Your Rechargeable Batteries Drain Completely Before Recharging Them?

February 17, 2016 | Elizabeth Knowles

Nokia phone with low battery
Photo credit: Martin Abegglen/Flickr (CC BY-SA 2.0)

Or is that an outdated practice?

It seems like there’s always contradictory tech advice going around: always let your batteries drain completely before recharging them so they’ll last longer, plug your batteries in when they’re between 25 and 75 percent full for maximum battery life, plug your batteries in whenever you feel like it.

How can you know which advice is best?

It turns out that the third suggestion is the most accurate; it really doesn’t make a difference when you decide to recharge your batteries. So how did the rumors start?

SEE ALSO: The Battery Bounce Test May Be Leading You Astray

It used to be that most rechargeable batteries were nicad (nickel cadmium) and nickel-metal hydride where a “build-up of crystals on the electrodes in the battery, leaving less room for the chemical reactions to take place there during charging” could cause your batteries to charge to a lesser and lesser extent, especially if you recharged them before they were fully drained, according to an ABC News article.

However, this isn’t a problem for the lithium ion batteries found in your computer and smartphone these days. In fact, letting your battery drain completely would destroy it. Don’t worry though; your devices have a safety mechanism that stops that from happening.

How does your rechargeable battery work? A chemical reaction happens inside it, which causes positively charged ions to travel through your battery and negatively charged electrons to travel through your device. When you plug it in to recharge it, the energy provided makes these chemical reactions happen in reverse so that your battery can start over again.

However, lithium batteries aren’t perfect. Some of the positive ions don’t get sent back to the negative electrode when the battery is recharged so it holds less and less of a charge over time. Furthermore, as the battery ages, the lithium particles clump together which means that there is less surface area for the chemical reaction to happen as the battery is being used.

Every once in awhile, it could be worth letting your battery go down to what it calls zero percent, simply to recalibrate the battery reading level — it has nothing to do with the battery’s actual life.

When your batteries do eventually die, make sure to dispose of them responsibly at a recycling facility.

Read more of our series on debunking science myths.

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