How should you charge your devices to maximize battery life?

The short answer

The three best ways to prolong the battery life of your devices are to avoid overheating, keep them charged between 20-80%, and use the official chargers your devices came with.

The long answer

As you might know from personal experience, battery capacity in phones, tablets, and laptops declines with age and use. First, let's dive into why these batteries can't last forever and then I'll cover the three most important guidelines to follow to maximize battery life.

Most modern devices use a lithium-ion battery for their rechargeable power sources. In a lithium-ion battery, lithium ions (represented as yellow Li circles in the diagram below) move from the positive (+) electrode to the negative (-) electrode while the battery is being charged. When the battery is being used to power a device, the lithium ions move back from the negative to the positive side, releasing the stored energy as electric current.

With each charge cycle, there is a tiny bit of damage caused to the battery. This damage makes it more difficult for the lithium ions to move between the electrodes. Plus, sometimes some lithium ions don't end up where they're supposed to be, reducing the number of ions available for storing and releasing energy. Over time, these issues add up, which means the battery can't hold as much charge as when it was new.

So you can't avoid your battery declining in performance over time, but there are three key strategies to maximizing its life (if you want to be a perfectionist about it):

Rule #1: Don't overheat your battery

In between the positive and negative electrodes, there is a layer of liquid electrolytes which allows the lithium ions to travel back and forth. When this liquid gets really hot, the electrolytes start to break down. You don't want that to happen because then the lithium ions will have a harder time moving back and forth between the electrodes in order to charge and power your device. So keep your devices away from direct sunlight, especially while they're charging.

Rule #2: Keep your devices charged between 20-80% as much as possible

Batteries are under the most strain when they are fully charged or nearly dead. This is because of an imbalance of ions between the positive and negative electrode layers.

When there are a ton of ions crammed on one side, the layer starts to physically expand which can cause degradation of the battery health. It's recommended you keep your device charged between 20-80% to help prevent these extremes. (Note: Read the section below to see if your phone does this for you as an automatic setting.)

Rule #3: Use your devices' official chargers

Chargers have a lot going on under the hood, and there are mechanisms and controls that have been designed to prolong your battery life. Your device's official chargers have likely been built to limit the amount of electrical current delivered and stop charging when it gets full. Off-brand chargers might not have such thorough safety settings, so it's always a good idea to stick with the one that your device came with.

🔋 Other interesting battery questions

I've heard it's a good idea to recalibrate your battery by letting it die and then fully charging it. Are you telling me that's bad advice?

If you find that your device suddenly shuts down despite having sufficient charge, has charge percentages stuck at a certain figure for a while, or is just really old, recalibration is likely a good idea.

Recalibrating helps keep charge estimates accurate by setting new anchors for a full charge and empty charge with your device's battery management system. Always follow your specific device's instructions on how to recalibrate effectively.

Don't Apple/Android phones have fancy technology to optimize battery health?

Yes, but it depends on how up-to-date your operating system and old your phone is. With iOS13, ​Apple released Optimized Battery Charging​ which delays charging past 80% in certain cases and uses machine learning to determine your charging habits. ​Android phones are more of a mixed bag​ in terms of this optimized charging setting.

Don't chargers automatically stop charging devices once they reach 100%?

Yes! Most modern chargers do have this "trickle charge" mechanism that cuts off charge once it's full and only tops off the charge when it's gone below a certain threshold. While this does reduce strain and overheating on the battery by cutting off charging, it does not solve for the problem of the battery simply being close to 100% full. Recall that balance of ions is best.

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Sources

Browne, G., & Reynolds, M. (2021, December 8). Here’s the truth behind the biggest (and dumbest) battery myths. WIRED UK. https://www.wired.co.uk/article/how-to-improve-battery-life-tips-myths-smartphones

Guy, N. (2020, September 4). Is Charging Your Phone All Day Really That Bad?. The New York Times. https://www.nytimes.com/2020/09/04/smarter-living/phone-charging-advice.html

Laudenio, L. (2022, December 12). Don’t Drain Your Phone’s Battery! The 20 to 80% Charge Rule Could Extend Its Life. LDL Travel Stories. https://ldltravelstories.com/tech/dont-drain-your-phones-battery-the-20-to-80-rule-could-extend-its-life/

Limer, E. (2022, May 4). How Best to Charge Your Phone, Explained by an Expert. Gear Patrol. https://www.gearpatrol.com/tech/a624169/smartphone-lithium-ion-charging-tips/

Triggs, R. (2023, March 25). How to maximize battery life: Charging habits and other tips. Android Authority. https://www.androidauthority.com/maximize-battery-life-882395/