What does a fast charger do to your phone's battery over time? How can you help extend your battery's life? We spoke to experts. Here's what we learned.
Does your phone last all day on a single charge? How about a year from now? Battery anxiety is real, and if you're contemplating a new phone like the iPhone SE, Samsung Galaxy A51 or OnePlus 8, its battery life is an increasingly important factor in deciding if that device is worth the money. As we expect more from our phones -- and want them to last longer -- the importance of an all-day charge has become a critical feature, alongside screen size and camera quality.
The enduring emphasis on battery life is one reason why fast chargers are now so ubiquitous, at least for high-end devices. The fastest, most power-delivering of all belong to premium phones like the Galaxy S20 and iPhone 11. If the battery threatens to drain before the end of the day, quickly recharging it with your lightning-fast quick charger is the next best thing. With fast-charging especially, a 10-minute charge can make the difference between going into an austere power-saving mode and losing power completely before you get home.
But now that fast charging is so readily available for phones, we have questions: Can a high-capacity charger damage your phone's battery in the short term? Can it degrade your phone's power-storing capability over time? And what causes unnecessary wear and tear on your phone's battery anyway?
To get the answers, we spoke with several battery researchers and engineers about the effects of quick charging on your phone's battery life. Here's what we learned.
Your phone battery isn't changing anytime soon
All mobile phones -- and most personal electronics and electric vehicles -- use lithium-ion (li-ion) rechargeable batteries. It's a tough slog to create batteries that last longer, because battery technology hasn't changed in decades. Instead, much of the recent progress in battery life has come from power-saving features built into devices and from making the software that manages charging and discharging more efficiently, so you sip power rather than guzzle it.
Unfortunately for mobile phones, the focus on extending battery life is generally on cars, satellites and your home's power system, areas where industrial batteries need to function far beyond the two or three years we expect from our mobile devices.
Another force working against our phones is their battery size. Compared to an electric car battery, a phone's power source is minute. For example, the Tesla 3's rechargeable battery has a battery capacity over 4,000 times greater than the iPhone 11 Pro Max.
The math gets a little complex because phone batteries are measured in milliampere-hours, while electric vehicle batteries are measured in watt-hours. But it's possible to draw equivalents. For instance, the Pixel 4 has a 2,800-mAh battery (or 10.6 Wh), and the iPhone 11 Pro Max reportedly comes with a 3,969-mAh battery (15.04 Wh). Meanwhile, the Chevy Volt uses an 18,400-Wh battery and a midrange Tesla Model 3 flaunts a 62,000-Wh battery.
That matters because the larger a battery is, the more battery-saving tricks there are to extend its life. For example, as you charge a battery, the voltage rises, putting it under stress, especially during the last 20% of the charge. To avoid this stress, electric car makers may charge new batteries just to 80%. Because of that larger battery capacity, the electric car still can still go an acceptable distance, while avoiding the stress of higher voltages. This can double the total lifetime of the car's battery.
Larger phone batteries can give you an all-day run time from a charge, but typically only at the full 100%. And while that lets the battery last for an acceptable time between charges, it also puts the battery under more stress from the higher voltage required to top it off.
You can't overcharge your phone battery
Overcharging used to cause anxiety among phone owners. The fear was that keeping a phone constantly plugged in could charge a battery beyond its capacity, making the battery unstable, which could degrade overall battery life or build up too much internal heat and cause the battery to burst or catch fire.
According to the experts we spoke with, however, a battery's management system is designed to shut off the electrical charge once a battery reaches 100%, before it can overcharge. You shouldn't let your battery drain to zero
At one time, you may have wanted to let your phone discharge all the way down once in a while to help the battery recalibrate its state of charge. But that's not so much of a problem with modern phone batteries.
In fact, discharging a battery all the way down can cause chemical reactions that over time can shorten a battery's life. To avoid a complete discharge, a battery's management system includes safety features that power down a phone when it reaches an energy level safely above empty. You only think you've hit zero when you see that last low-battery warning.High temperatures can damage your battery
Heat is a true enemy to your battery. High temperatures are known to reduce a battery's lifespan over time.
You'll want to keep your phone out of strong sun, away from window sills and off the dashboard of your car to prevent overheating, which can make the battery less efficient over time. In extreme cases, an overheated battery could explode. Mismatched chargers and cables won't harm your battery
Unless you're using counterfeit or damaged chargers and cables, mixing and matching cables and chargers is not going to harm your battery. However, you may not be charging up quickly as possible as when you use the ones that came with your device.