Chapter in this post:
I admit that this claim sounds like clickbait, but I didn't mean to downplay the problem with a “maybe” or “maybe” in the headline because I think it's actually serious.
But let's start at the beginning ...
When I received my iPhone 12 Pro with MagSafe, I directly measured the performance (read here "MagSafe charging power measured“) That is used when loading.
The result: The high performance that MagSafe offers when charging, according to Apple, only flows for the first few minutes. Then the charging electronics throttle the power so that most of the time only about 5 watts flow into the iPhone 12 Pro. So most of the time you charge as slowly as with the old 5-watt plug-in power supply units that you used to get with your iPhone. Nevertheless, the iPhone heats up significantly more than is the case with wired charging.
In my opinion, the reason for the slow - apparently artificially slowed down charging via MagSafe - is that the heat generated by the wireless, lossy charging is very strong, but the battery must not exceed a certain temperature when charging.
The fact that I am not alone with the high levels of warming during wireless charging also shows this entry in the Apple support forum.
I once translated the thread in part (with DeepL):
When I charge my iPhone 12 Pro overnight using MagSafe, both the charger and the phone feel hot or warm in the morning, as if I've played a graphics-intensive game for a while. I am concerned that this means that my phone has been in a heated / warm state for the 8 hours that it was charged overnight. That doesn't seem to be good for battery life.
The forum thread is even longer, but in principle these lines are enough. With him, too, the iPhone gets quite warm thanks to MagSafe. For me it was about 37 ° C that I got with the app Coconut battery could measure.
Admittedly: 37 ° C doesn't sound like much, but if you hold your iPhone in your hand, it feels quite warm - sometimes even hot. But in order to contribute a bit of facts, I did some research to determine the “warmth” at which a smartphone battery can actually be damaged.
The website Wissenschaft-im-Dialog.de has this an interesting article, which draws a comfort limit for the battery at 35 ° C:
Over the years, the electrode materials begin to react with the electrolyte, but also with other materials, and they are increasingly unable to store the lithium ions. If we expose the smartphone to high temperatures of 35 degrees Celsius for too long, the electrodes react faster, which accelerates the aging process of the battery. The battery now has to work a lot harder to provide the same performance.
With the 37 ° C, which I measured with Coconut Battery, we are slightly above this limit.
Now we have actually already proven it: The iPhone heats up to more than 35 ° C when charging via MagSafe and this - scientifically proven - reduces the battery capacity over the long term. This may not take on tragic proportions if you only charge the iPhone here and there with MagSafe, but if you put your iPhone on the MagSafe charging puck overnight and thus "keep it warm" for hours, the battery is not doing the battery any good.
In the case of the iPhone, the battery health value is below Settings> Battery> Battery status> Maximum capacity displayed.
The following article is interesting (and the actual reason for my blog post) in this context Medium.com. An iPhone user describes how much the maximum capacity of his iPhone 12 Pro has decreased due to constant charging with MagSafe. Here are his two most important statements:
His iPhone 12 Pro has lost a lot more capacity than his iPhone 11 Pro - even though he has been using the iPhone 11 Pro for a significantly longer period of time. From his point of view, the reason for this is to be found in the nightly charging via MagSafe and the resulting warming of the iPhone.
And shows that the user is not an isolated case above this thread in the apple forum. A quote from there:
I bought my iPhone 12 Mini 4 months ago. Battery condition> maximum capacity is already at 90%. Normal use, battery lasts for one day, charge at night with MagSafe. Have others had similar experiences?
By the way: The “magic limit” above which the iPhone reports that the battery should be replaced is 80%. The user's iPhone 12 Pro is not far away from this and that after less than a year of use.
The two values and the statement in the article about the relationship between battery health and temperature only allow one conclusion for me: Charging with MagSafe is not "healthy" for the battery, or the battery ages faster than when you use the iPhone Charging the cable.
However, you also have to keep in mind that fast charging via USB-C cable also generates more heat than charging with an "old" USB-A-to-Lightning cable. In my tests with USB-C charging cables, I did not get over 37 °C but also 36,5 °C when charging. Accordingly, charging via USB-C is not the best alternative - but at least the best compromise between "fast" and "battery-friendly".
The first choice for "healthy" charging is a charging cable that has a USB-A connector on one side and a Lightning connector on the other. The iPhone needs almost twice as long with this cable as with the USB-C fast charging cable, but this makes no difference when charging overnight and it saves the battery.
Since I know that some readers cannot do anything with "USB-A-to-Lightning cable", I would like to give you a direct purchase recommendation here:
If you like to charge your iPhone quickly, but still want to go to work halfway battery-saving, you will find the right combination here:
I think Apple is well aware of the problem. Accordingly, they should continue to make efforts to make wireless charging even more efficient. Ultimately, it is the loss of energy that heats up the battery in the form of waste heat. If you can manage to reduce this loss, you should also reduce the negative impact on battery life.
At the moment, the few degrees Celsius that the iPhone heats up to over 35 degrees during MagSafe charging seem to be the problem. If Apple were to change the software of the charging electronics in such a way that, for example, it already reduces the charging current at 34 ° C, then the loss of maximum capacity would possibly be significantly lower.
Of course, this would also increase the loading time of the iPhone via MagSafe, but the bottom line is that this should be ok for most users. Nobody uses wireless charging (even with MagSafe) because it would be particularly fast. In fact, using MagSafe, the iPhone takes roughly twice as long to charge its battery than charging it with a USB-C fast-charging cable.
The good news: Apple could deliver the changes to the loading software without any problems with a firmware update and thus provide an improvement relatively easily.
The “optimized charging”, which Apple delivered a few months ago, should also be a step in the right direction. But despite everything, my iPhone 12 Pro Max still heats up to almost 37 ° C when the MagSafe is charging - I think there is still a need for improvement. Whether this happens naturally is another question. Let us surprise.
Jens has been running the blog since 2012. He appears as Sir Apfelot for his readers and helps them with problems of a technical nature. In his free time he drives electric unicycles, takes photos (preferably with his iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions for current bugs.