I stopped this common charging habit that was silently draining my iPhone’s battery

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ZDNET Highlights

• Extreme temperatures are a major factor in premature battery failure.
• Car charging is a perfect storm when it comes to overheating.
• You can still charge in the car, but you have to take some precautions.

I’ve been tracking the battery health of my daily driver iPhones for so long that it’s practically second nature. It’s like a weird hobby/habit I’ve picked up. Ever since I got my iPhone 17 Pro Max, every few days I’ve been firing up the Settings app and taking a look at my battery stats. I’m particularly curious because, with this handset, I’ve decided to ignore caution (and Apple’s battery care tips).

Also: I spent 2 years charging my phone exactly as Apple suggests – where is it all this time

Why? Well, I followed all the rules with my previous iPhone. I turned on optimized battery charging, took care not to leave the phone on charge for hours, and also did my best to keep it cool. Despite all this, the battery barely lasted two years and deteriorated so much that it became frustrating to use, and the handset I had planned to keep for three years ended up being replaced after only two years.

So, this time I stopped caring. No fee limits, no fancy customization. I just threw it on any charger or used any power bank that was close at hand.

There was one thing I changed.

car charging dilemma

I spend a lot of time in cars. And putting my phone on charge is as much of a ritual as putting on a seat belt.

But here’s something that I’ve noticed has become an increasing problem, especially over the last few years. No matter how I charge my phone, whether it’s wired, wireless in the dock, or using the car’s built-in charging pad, my phone always overheats. And I don’t just mean a little hot, I mean HOT.

Also: After testing this Anker, I wish every wireless charger had a thermoelectric cooler

Cars are a strange thing. In the summer they’re like greenhouses on wheels, and in the winter we’re putting heat into them to keep them warm. And the purpose of that cooling and heating is to keep humans comfortable. The phone is usually on the dash, in the window, in front of a vent, or in a crack.

It’s a hard life for a phone.

Another thing I noticed is that I’ve only seen my iPhone enter “charging on hold” mode (a mode where it stops charging to cool down) when it’s on charge in the car. I haven’t noticed this happening when it’s connected to a power bank, or when it’s charging on my nightstand.

This happens only when he is in the car.

heat is the enemy of batteries

Heat is harmful to batteries, and Extreme heat is known to accelerate chemical corrosionWhich leads to premature failure.

Apple has a lot to say on the subject of summer.

Also: iPhone charging slowly? 6 Quick Solutions Worth Trying Before Blaming Your Battery

iPhone (and iPad, iPod, and Apple Watch) all work best at 32° to 95° F (0° to 35° C), and the company warns that “It is especially important to protect your device from exposing it to ambient temperatures above 95° F (35° C), which could permanently damage battery capacity.”

The interior of a car can very quickly reach the point where it is bad for the battery (and humans!). here is one calculator Based on a study from Stanford University School of Medicine. Even on a day with mild 70°F (21°C) temperatures, the car’s interior 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 reach 118°F (48°C) in one hour. And a Texas summer high of 98°F (37°C) will raise the internal temperature to 123°F (52°C) in half an hour.

Also: 12+ iPhone Settings You Can Change to Improve Its Battery Life (iOS 26 and Older)

Batteries are going to die – you can’t change the laws of physics – but you can give them a fighting chance. Apple itself warns that high temperatures can permanently reduce battery capacity (which is why iPhones go into “charging on hold” mode when things get too hot).

So, I decided to stop charging my phone in the car altogether. Well, almost. I’ll get to the exceptions in a moment.

results so far

This small change seems to bring appreciable change. My iPhone is currently at 196 recharge cycles, and the battery health is still at 100%. This is impressive, with Apple claiming that the new iPhone batteries are designed to retain up to 80% of their original capacity after 1,000 full charge cycles.

At about 200 cycles, I’m already 20% into it 1,000-cycle lifetime Apple estimatesAnd yet there is no change in the health of my battery.

In February, I wrote about how amazed I was that my phone had completed 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 defying the laws of battery physics – it’s not, it’s just proof that listening to science and avoiding heat really does help.

Exception

Now, I’d be lying if I said I never charge my phone in the car anymore. Sometimes, life happens, and I need a quick top-up when I’m on the move. But when I do this, I take some precautions. I ensure that the phone is kept away from direct sunlight and heaters. If it’s a very hot day, I’ll try my best to keep my phone near an AC air vent.

Plus: Why this MagSafe battery pack is our readers’ favorite model right now — especially at its price

Also, I have replaced all my in-car chargers with such chargers use thermoelectric cooling To actively cool the iPhone while charging (more info on thermoelectric coolers here).

None of these are perfect, but I’m not perfect either, so it’s a compromise I’m happy to live with.

What about those built-in charging pads?

Overall, they are terrible.

This is partly due to the fact that my iPhone 17 Pro Max is too big to fit into most charging pads, and because I have it in a big, thick case, but also because they’re so poorly designed that most phones — especially those with the “camera bump” — don’t interface adequately with chargers.

I rent a lot of vehicles for travel, and I always try to have a charging pad if one is available, and I can’t think of any that I have that, in the words of the late Apple CEO Steve Jobs, “just works.” They seem to work better with smaller handsets, but the experience still isn’t great.

Also: Setting up a MagSafe charger on my nightstand was the iPhone upgrade I didn’t need

Every handset I’ve tried on every charging pad I’ve used in the car has gotten unacceptably hot.

It’s shocking that companies that can make cars can’t create a good in-car charging experience.