iPhone X 29W fast-charging, is it hard on battery lifespan?

The answer is complicated. I know that every complex problem has a simple solution - but it's wrong.

My first choice would be to use the 5W USB power adapter that comes with the phone, and charge overnight, so you don't really care how long it takes. It's what I've done with every iPhone. It supplies 1 amp.

The 12W iPad adapter can supply 2.4 amps, but the most the X can use is 2 amps, and it only uses that for the first 70% of state of charge; it then tapers down to zero at 100%. So it doesn't use it for long enough to overheat the phone.

The 29W USB-C adapter can supply 5.8 amps, but again, the most the X can use is 2 amps, so it's the same as the 12 W. (The amount an adapter can supply is irrelevant; the device determines how much current goes into it. Thus, you could also use a 70W USB-C adapter and the answer would be the same.)

A Qi wireless charging pad can also be used; the phone will use 7.5 watts or 1.5 amps, so it is sort of in between.

So I guess the answer is use a 12 W or 29 W if you are in a hurry, or a 5 W if you are not. None of the choices will make much difference in the life of the battery, which is determined primarily by the number of full charge cycles rather than the charging time.

Doesn't matter what the charger can supply, the phone will only use (draw) the wattage it needs.

No different than plugging that 29 watt charger into a 20 amp wall socket, which is typical of most homes in the U.S. If it didn't work that way, you'd burn up most of your devices you plug into a 20 amp circuit. The device (light bulb, toaster, television) only draws what it needs and supplying more than it needs won't hurt it.

William Kucharski wrote:

No, it will not adversely affect battery life.

Lawrence is right that it might theoretically make a difference in battery longevity, but is it really worth worrying about it? If the convenience to the user is greater than the cost of replacing the battery sooner, then go for the convenience. I personally don't connect to anything that can't charge at the maximum charge rate.

Use either one. The ratings that you are quoting are CAPACITY. Actual charge current is controlled by the phone.

y_p_w wrote:

Lawrence Finch wrote:

Why buy a more expensive USB adapter if you don't need one?

Kind of an old thread, but Apple charges the same price for the 5W/10W/12W USB-A power adapters.

Yes, but the 5W is FREE, which is what I meant. You would have to pay for a 10W/12W (or 29W). So a 12W costs infinitely more than a 5W.

Also - Apple claims that the iPhone 8/8+/X charges even faster on a USB-C power supply with the Apple USB-C to Lightning cable. Probably more than the standard 2100 mA, but they don't specify the rate other than "50 percent in 30 minutes".

Fast charge your iPhone X, iPhone 8, or iPhone 8 Plus - Apple Support

The 29W says 5.2V at 2.4A.

5.2v x 2.4A = 12.48W, the same as the 12W iPad USB adapter. The battery in the 8 Plus is 2675 MaH and the 8 is 1821 MaH. As the claim is 50% in 30 minutes, that means it charges an 8+ to 1330 MaH in that time, or a rate of 2.675 AH discounting energy lost to heat (probably around 10%). However, the battery is not flat when you start charging thanks to the safety factor that 0% is not a fully discharged battery. So most likely the maximum charging rate is around 2.4A. If I had an 8+ I'd measure it. My 7 Plus charges at 2 A initially, and takes about 45 minutes to 50%, but it has a larger battery than the 8 Plus.

What that note doesn't bother to point out is that the rate of charge declines after 80% is reached, so that last 50% will probably take an additional hour.

It's not higher current. Actual charge current is controlled by the phone.

Everything I have read goes with #2

2) Modern day phones are engineered to charge faster, this therefore will not have any negative impact on the batteries overall lifespan.

No, it will not adversely affect battery life.

No, it will not damage the battery.

If the supplied voltage is correct at 5 volts DC, the current can be a million amps, and the iPhone charging circuit will still only use the current it requires to charge the battery.

jessemooney wrote:

So when the phone uses a higher charge current will that degrade the battery faster (this is in regards to fast charging)?

Obviously if it is too high it will instantly fry the battery (which the phone would not allow anyways).

oops, I didn't see this post before responding. No, you could use a power adapter that could supply, say, 1,000 amps, but it wouldn't do any harm because the phone would still use only 2 amps.

Think about your home power; does the fact that your incoming power can supply 200 amps instantly burn out all of your light bulbs and appliances?

Lawrence Finch wrote:

Why buy a more expensive USB adapter if you don't need one?

Kind of an old thread, but Apple charges the same price for the 5W/10W/12W USB-A power adapters. There are also good quality non-Apple power adapters (like from a Samsung phone).

I get what you're saying about perhaps slowing it down to minimize the heat and theoretically increase battery longevity. However, a lot of stuff with batteries is about balancing longevity with convenience.

Also - Apple claims that the iPhone 8/8+/X charges even faster on a USB-C power supply with the Apple USB-C to Lighning cable. Probably more than the standard 2100 mA, but they don't specify the rate other than "50 percent in 30 minutes".

Fast charge your iPhone X, iPhone 8, or iPhone 8 Plus - Apple Support

The 29W says 5.2V at 2.4A.

Less available current = lower temperatures as well as a longer time to charge.