The latest record reduced the charging of a mobile phone to an incredible five minutes. Chinese manufacturer Redmi showed the a new version of the phone Note 12 Discovery Edition with a battery with a capacity of 4100 mAh. The charger can fill this accumulator “from zero to one hundred” in less than five minutes.
Watch a demonstration of rapid charging (time-lapse):
Record-fast charging of the test version of the Redmi Note 12 Discovery Edition phoneVideo: Pavel Kasík, Seznam Zpravy
The charging dynamics can also be deduced from the published video. The manufacturer states a maximum charging power of 300 watts, in the charging demo it “only” reaches just over 290 W. The power is of course the highest at the beginning of charging. After three minutes, when the indicator is at 70 percent, the charging speed gradually decreases.
It also means that just three minutes of charging should last you about a day of normal phone use. Charging in this technical demo is apparently deliberately optimized so that the indicator reaches one hundred percent just before the five-minute mark.
This particular record holder is not yet on the market. And it’s not certain when or if this particular version will go on sale. However, it is a demonstration of what is technically possible.
Another Chinese manufacturer Realme this year demonstrated charging at a speed of 240 W, which corresponds to filling a 4600 mAh battery in less than 10 minutes.
Doesn’t it harm the batteries?
In recent years, phone charging has become significantly faster. While still in 2013 the highest charging power was around 10 watts, in 2018 it was already fifty watts and in 2021 even 120 watts. This corresponds to a charging performance comparable to a powerful laptop charger.
Fast charging offers manufacturers a way to differentiate themselves from the competition. It then makes life easier for users and has largely solved the “endurance fear” that most first-generation smartphone users had. However, the question arises as to whether it is harmful to the battery. The answer is not entirely straightforward.
The battery in a smartphone works on the principle of a chemical reaction. Specifically, Li-Ion batteries use the movement of lithium ions between the cathode and the anode.
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The faster it should be charged (or discharged), the faster the exchange of charged particles between the two electrodes should take place. The main limitation is the speed with which the corresponding chemical reaction can take place in the battery, explains Pavel Hrzina from the Department of Electrical Technology, FEL of the Czech Technical University. “To simplify, it is possible to imagine that in the case of a thick layer of active matter, it will take longer for the battery to charge, that is, for all the matter to be used for accumulation.”
Designers are understandably well aware of this limitation. Batteries intended for electronics therefore have layers of active matter that are very thin. “If the charging power is sufficient, the reaction can take place over a large area,” says Hrzina.
In other words, in a properly built battery, and most batteries for mobile phones, for example, are built today for fast charging, the chemical processes necessary for charging can take place quickly.
The worst is the heating
This does not mean that they cannot be damaged by such high power charging. For example, batteries can be built in such a way that they can charge unevenly and thus damage themselves. “Local inhomogeneities can appear, some parts of the battery can charge earlier than the rest, and then they are overloaded,” explains Hrzina.
Excessive heating of the battery by waste heat is also a danger for reducing the service life with fast charging. Charging is never completely efficient and some of the electricity is turned into heat. And higher temperatures are harmful to batteries, not to mention the risk of ignition.
Slow charging is more favorable in this regard, because there is significantly less waste heat. Charging power of 4.5 watts (USB 3.0) or 300 watts makes a huge difference. In the second case, approximately 70 times more heat is produced, which must be removed somewhere. And since phones don’t have any “cooling circuits” it has to be passively dissipated across the battery and phone.
“There is a direct connection between the reduction of the service life and the heating of the battery as a result of these so-called ohmic losses,” says Pavel Hrzina. However, rapid charging is not only worse for batteries, the Czech expert points out: “Lithiums are not very good if we keep them on the charger for a long time.”
Therefore, fast charging does not last all the time and the performance gradually decreases. “You can think of a battery as a sponge,” described Arthur Shi of iFixit. “When you first pour water on a dry sponge, it soaks in quickly. This corresponds to the fast charging phase of the battery. “But if you continue to pour water on an increasingly wet sponge at the same rate, the liquid will begin to pool on the surface because the partially soaked sponge cannot absorb as much water.
It depends on the tuning
Therefore, in the end, the lifetime of the battery is determined by how much attention the designers and manufacturers paid both to the design and production of the battery itself, as well as to its support system: “Currently, the life of the battery is primarily determined by the system that controls its operation,” points out Hrzina. That is, electronics and control software that monitor operating parameters and do not allow them to be exceeded.
The system takes care, for example, that the voltage on the cell does not exceed some given maximum values, that the battery does not charge too quickly if it has a low temperature, that it does not discharge too quickly, and other parameters. Even with batteries, it depends primarily on how it is handled.
So the life of the battery largely depends on what the manufacturer did for its longevity before you even got the phone in your hand. Paradoxically, races in charging speed can lead to deterioration of long-term endurance. While the charging speed can be demonstrated in one short video, the long-term battery life proves to be more difficult.
