Credit: Daniel Korpai

What the Research Says

As you might know, heat is one of the worst things for your iPhone’s battery. If your lithium-ion battery is stored or operated at elevated temperatures for any length of time, it can reduce its overall lifespan — killing your day-to-day battery life in the process.

In a nutshell, Qi-based inductive wireless charging may be worse for your battery than standard wired charging due to heat.

When it comes to Qi-based wireless charging, heat is a problem because both the charger and the device radiate heat. The fact that a smartphone and a charging surface are often touching each other just makes the situation worse.

In other words, because there are “limited opportunities to dissipate heat or shield (an iPhone)”, charging inductively can heat up your battery more than traditional wired chargers.

Worse still, the researchers found that if the coils in your smartphone and the coils on the charging pad aren’t properly aligned, the whole setup can get even hotter. That’s because Qi charging systems typically bump up the power to adjust for the poor alignment — which isn’t always obvious to the consumer.

When it came to hard numbers, researchers compared smartphones charged by traditional means, properly aligned wireless charging, and purposely misaligned wireless charging.

1. A properly aligned charger actually reached temperatures about seven degrees hotter than traditional means (though the temperature gradually tapered off).
2. A misaligned charger reached around the same temperature, but much sooner. The heat also persisted for longer.
3. The researchers concluded that inductive charging is “likely” to lead to a reduction in overall battery lifespan.

How to Charge Safely

If you’d still like to use wireless chargers but want to extend the longevity of your battery, here are a few tips to keep in mind.

• Make sure the coils are aligned. While it may be hard to tell, you’ll want to ensure that the charging coils on your iPhone and the charging coils on the wireless charger are properly aligned. Refer to your chargers manual if you need help.
• Don’t charge in heat. Make sure that your iPhone isn’t in direct sunlight or a hot environment when you’re charging it.
• Avoid using it while it’s charging. Running CPU-intensive apps on a charging iPhone can cause it to heat up. If you have to use your iPhone while it’s charging wirelessly, at least try to avoid games or other resource-heavy apps.
• Take off the case. It isn’t strictly necessary to remove a case before charging, but Apple recommends it. Certain cases could prevent an iPhone from cooling off properly during charging.
• Use a charger with a fan. It might be worth investing in a Qi wireless charger that comes with its own cooling system, such as a fan. (You could also just point a fan at your iPhone and wireless charger while it’s charging.)

While not directly related to heat, iOS 13 also comes with a new Optimized Battery Charging feature that could also extend the longevity of your battery. We recommend flipping it on and keeping other battery best practices in mind.