Can use iPad 12W charger to charge iPhone 6s Plus without any risks?

See Charge your iPhone with an iPad or Mac notebook power adapter - Apple Support

The primary answer is "yes," you CAN use the 12W charger with no risk. The rating is the maximum capability of the charger. Actual power draw is controlled by the receiving device (the iPhone) and the 12W charger will cause no additional heat.

I don't have exact figures regarding current but my experiences regarding how long it takes to charge suggests that the 12W charger will put out a bit more current.

I have measured the charging current for iPhone 6 and 7 (I skipped the 6S). For an iPhone 6 the initial current (when the phone is below 70%) is 1.5 amps, so it will charge to the 80% level 50% faster. For an iPhone 7 Plus it is 2 amps, so it will charge to 80% twice as fast. Note that above 80% the charging rate slows to approach 100%, but not exceed it. So the total charging time will not be 50% faster or twice as fast, but it will still be a lot faster than the 1 amp (5 watt) cube.

That said, as I charge overnight, every night, I don't really care how long it takes to charge.

torakaru wrote:

Firstly thanks a lot by participating in this topic. Did you check (or notice) any difference in temperature (at back side of any of your both iPhone 6 or 7) when did you charge them with the 12W?

Any kind of overheating (even if small one compared with using the 5W adapter?)

If not done yet, may I ask you the next time that you charge your iPhones to try to charge the iPhone 6 with the 5W and the 7 with the 12W and take a look to their back respective temperatures, at least the first minutes when you begin to charge them, please?

(I don't know if you have any kind of temperature sensor to measure their backs during charging state to compare how affects to the iPhone 6 the charging difference from 0-80% between the 5W adapter (1A consumption) and the 12W adapter (1.5A), please.)

In any case, thanks by your contributions Lawrence! ;-)

Well, I don't have the 6 anymore. And all iPhones have an overheat sensor, and they will shut off if they overheat, so that's not something to be concerned about. Any device will get warmer at higher charging currents, but it has never gotten as hot as it does when I use the camera for more than a few minutes, or play an interactive game. If you think about it, when you charge any device heat will be generated, because no process can be 100% efficient (2nd law of thermodynamics). Some of that heat is from the battery itself, some from losses in the charging circuit. But the total heat load for any charge cycle will be the same, regardless of the charging current. At a higher charging current it will get warmer, but for a shorter period of time, than at a lower charging current that takes longer. Same BTUs, however.

I do have a precision laser temperature gauge; when I get a chance I will see what the differential heat load is for the cube vs the 12 W adapter for my 7+.

I have charged my iPhone several times from a 500W lab-grade power supply. Its the phone that decides how much current it takes - the charger only decides about voltage. In general one should use only original or certified chargers.

torakaru wrote:

Hi Lawrence,

Thanks a lot, it is a pity that you have not anymore the iPhone 6 to perform the temperature quick experiment with the 5W and 12W adapters; but if your iPhone 7 Plus is drawing 2A when the 12W adapter is used, it will be a very good candidate for this experiment.

The only charger I ever used with my iPhone 6 was the 12W. There was no way I was going to carry two chargers around. I had the phone for almost two years. The last I used it and checked the battery health, It was still very good.

You're way over thinking this. All cell phone batteries will lose capacity over time. What charger you have makes no difference in that.

The only power supply I carry with me in my briefcase is one of my iPad 12W ones. I‘ve used it numerous times to charge an iPhone 5, 6 and now 7. Never had an issue.

Don't take offense but you are over-analyzing the situation. You have been told by several experienced individuals that there is no problem. If you're still concerned, don't do it - the benefit isn't all that great.

torakaru wrote:

And to don't bother you more times, and in case you may be to be so kind to decide to make this last experiment with the 5W adapter: may you also at same time quick check the temperature change in the 5W adapter itself? I am hearing many people about the pretty bad building quality of it (Apple's 5W adapter), that it breaks easily after few months, and even it gets considerably hot; this last thing is also mentioned in its Apple's manual, although Apple officially states there that it is still in the safety surface temperature limits of IEC 60950-1).

I've monitored the input power to the cube with a Kill-a-Watt meter. When charging the cube consumes 6.4 watts, and outputs 5 watts, so the loss is 1.4 watts. It can't possibly generate measurable heat with a 1.4 watt loss. The temperature of the cube goes up by 1.5ºC. and the phone goes up by about 2ºC.

When I switched to the 12 W adapter it consumes 9 watts when charging at 8 watts (1.6 A), so it is slightly more efficient. Neither consumes any power with no load connected.

I have never had a 5W cube break down, and my oldest one goes back to my first iPhone in 2007. I still use it.

However, there are a number of counterfeit cubes on the market, that are cheaply designed and actively dangerous to use. Here are 2 videos about counterfeits:

Apple iPod chargers - fake versus genuine - YouTube

EEVblog #388 - Fake Apple USB Charger Teardown - YouTube

I’ve been doing it for years with no problems but, if you’re concerned, it’s not that big a deal to simply avoid using the 12W.

Just an anecdote:

I have a 12w iPad charger that I got with my iPad1 that sits next to my chair (you know, the one you sit in every night - your chair - ANYWAY).

Because it it convenient, I have always used it to charge all of my iPhones over the years: iPhone 4, iPhone 5s, and now iPhone 7s Plus.

I have never had any noticeable issues with battery life or otherwise by using this practice 🙂

Cheers,

GB

torakaru wrote:

It will be very helpful if next time that you fully discharge a couple of times both of your devices, you charge them one time with your original 5W adapter, and another with the 12W, and monitor the chraging time to see the differences between both in both iPhones.

Personally, I rarely fully discharge my phone. I charge it overnight so I would have no way of knowing how long it took to charge. And, I gave away my original iPhone chargers. I only keep the iPad chargers.

Once again, you are way, way overthinking this. Put your phone on to charge overnight.