Want to protect your iPhone's battery health? Stop doing this

I receive a lot of questions about the iPhone "battery health" figure. But If you're one of the few people who doesn't know what I'm talking about, let me introduce you to this: tap on Settings, then Battery, followed by Battery Health. You'll find Maximum Capacity, which Apple describes as "a measure of battery capacity relative to when it was new."

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I've been keeping track of this number on my iPhone, and on November 4, it finally ticked down one percentage point to 99% after 205 recharge cycles. Impressive, right? My iPhone's battery must be made of unobtanium or something and will last forever, right?

However, this morning, after only eight more recharge cycles, it ticked down another percentage point. So what gives? Surely something must be wrong with my battery. Is it time for a strongly worded tweet directed at Apple CEO Tim Cook?

No, I won't be doing that. In fact, I was expecting this to happen, and the battery is behaving as it should. 

The weather has shifted from warm to chilly here in the UK over the past week and I've been using and charging my iPhone in colder temperatures. Batteries are sensitive to temperature changes, and they prefer the sorts of temperatures that we humans like. Stray even a few degrees away from comfortable room temperature, and batteries won't be able to hold as much charge, can't put out the same power, and wear at a much faster rate than if kept at a stable room temperature.

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This is precisely why you should try to keep your iPhone and any other device containing a battery -- at around 18°C/64°F, give or take a couple of degrees. Stray beyond this, and your battery will feel additional strain and wear faster; go too far outside this range, and most devices will prevent you from recharging the battery until temperatures return closer to this ideal point.

Like I keep saying, the best way to take care of your iPhone's battery -- or any other rechargeable battery, (though iPhone owners are the ones most obsessed with this ) -- is to charge and discharge the battery as close to room temperature as possible. Don't bake your iPhone on a car dashboard during a hot day, and don't let it freeze in the depths of winter.

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But what if I return to charging my iPhone's battery at room temperature? Will the Maximum Capacity ratchet up a notch? 

Unfortunately, the answer is no.

Whenever this number ticks down, it's a one-way trip. Other than replacing the battery entirely which causes the maximum capacity number to go up, I have not found another way to increase the battery figure. But think of it as a worse-case measure of the battery's capacity rather than a dynamic figure. 

Or, just stop thinking about this number because it's fickle and get on with life.