Is silently killing your iPhone battery! The common charging habit quietly destroying the battery of my iPhone? – here’s the fix

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Key Points from ZDNET

• High temperatures significantly contribute to early battery deterioration.
• Charging your phone in a car creates ideal conditions for overheating.
• You can still charge your device in the vehicle, but certain precautions are necessary.

I’ve been monitoring the battery condition of my primary iPhones for so long that it’s become almost automatic. It’s like an unusual hobby or routine I’ve developed. Every few days since I received my iPhone 17 Pro Max, I’ve been opening the Settings app and checking my battery statistics. I’m especially interested because, with this device, I decided to disregard caution (and Apple’s battery maintenance advice).

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Why? Well, I adhered to all the guidelines with my previous iPhone. I enabled Optimized Battery Charging, was careful not to leave the phone charging for extended periods, and even tried my best to keep it cool. Despite all these efforts, the battery barely lasted two years before it became so poor it was annoying to use, and a device I’d intended to keep for three years was replaced after just two.

So, this time I stopped worrying. No charging restrictions, no special optimizations. I simply placed it on whatever charger or grabbed any power bank that was nearby.

There was one thing I altered.

The challenge of car charging

I spend a considerable amount of time in vehicles. And placing my phone on charge is just as much of a habit as fastening my seatbelt.

But here’s something I’ve noticed has become a growing issue, particularly in recent years. No matter how I charge my phone, whether it’s through a cable, wirelessly in a dock, or using the car’s integrated charging pad, my phone always becomes hot. And I don’t just mean slightly warm, I mean really hot.

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Vehicles are peculiar. In summer they’re like mobile greenhouses, and in winter we’re pumping heat into them to warm them up. And that cooling and heating is designed to keep the people comfortable. The phone is usually on the dashboard, by the window, in front of a vent, or in a tight space.

It’s a difficult existence for a phone.

Something else I observed was that the only time I have ever seen my iPhone activate “Charging on Hold” mode (a feature where it temporarily stops charging to cool down) is when it’s charging in the car. I haven’t witnessed this occur when it’s connected to a power bank, or when it’s charging on my bedside table.

It’s only when it’s in the vehicle.

Heat damages batteries

Heat is harmful to batteries, and extreme heat is known to speed up chemical breakdown, resulting in early failure.

Apple has plenty to say regarding heat.

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The iPhone (and iPad, iPod, and Apple Watch) all function best at 32° to 95° F (0° to 35° C), and the company cautions that it is “especially important to avoid exposing your device to ambient temperatures higher than 95° F (35° C), which can permanently damage battery capacity.”

The inside of a car can quickly reach levels that are harmful for batteries (and people!) very rapidly. Here’s a calculator based on a Stanford University School of Medicine study. Even on a moderate 70°F (21°C) day, the inside of a car can reach 104°F (40°C) in just 30 minutes and 113°F (45°C) after an hour. Increase the temperature to 75°F (24°C), and the internal temperature will exceed 118°F (48°C) in an hour. And a Texas summer peak of 98°F (37°C) will drive the interior temperature to a scorching 123°F (52°C) in half an hour.

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Batteries will eventually fail — you can’t alter the laws of physics — but you can give them a better chance. Apple itself warns that high temperatures can permanently decrease battery capacity (this is why iPhones enter a “Charging on Hold” mode when things get too hot).

So, I decided to completely stop charging my phone in the car. Well, almost. I’ll explain the exception shortly.

The outcomes so far

This single small adjustment appears to be making a noticeable difference. My iPhone is currently at 196 recharge cycles, and the battery health remains at 100%. That’s remarkable, considering Apple claims newer iPhone batteries are engineered to retain up to 80% of their original capacity after 1,000 full charge cycles.

At nearly 200 cycles, I’m already 20% into the 1,000-cycle lifespan Apple estimates, and yet my battery health hasn’t changed.

Back in February, I wrote about how astonished I was that my phone had reached 122 recharge cycles without dropping to 99% battery health. Now, at 216 days old and almost 200 cycles, I’m even more impressed. It’s almost as if my iPhone is challenging the laws of battery physics — it’s not, it’s just evidence that following the science and avoiding heat truly does help.

The exceptions

Now, I’d be dishonest if I said I never charge my phone in the car anymore. Sometimes, circumstances arise, and I need a quick boost while I’m traveling. But when I do, I take several precautions. I make certain to keep the phone out of direct sunlight and away from the heater. I’ll even try my best to position my phone near an air vent with the AC running if it’s an especially hot day.

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Additionally, I’ve swapped all my in-car chargers with ones that utilize thermoelectric cooling to actively cool the iPhone while it’s charging (more details on thermoelectric coolers here).