Wired
I want to ask you something: “Did your phone be inexplicably turned off in winter?”
In fact, if you look carefully, you can find that the parameter page of the mobile phone generally indicates that the operating temperature is between 0 and 35 degrees.
However, in real life, in many places, it is unavoidable that the mobile phone is working below zero as soon as you go out in winter. So today we will simply find 30 mainstream mobile phones, at our own expense, use a crane to build a cold storage downstairs in the company, to add something about which mobile phone is more cold-resistant.
Cold storage discharge test
We selected mainstream new models of common brands currently on the market, and based on e-commerce sales data, we respectively selected a flagship model, a mid-range model, and a low-end model with better sales under the brand for testing.
The internal temperature of the cold storage is a constant temperature of minus 15 degrees, which is not much different from the outdoor temperature in the northeast in winter. Let’s perform the first round of discharge test. All 30 mobile phones have been fully charged. At the same time, in order to use the scene as close to reality as possible, let them shoot time-lapse videos at the same interval at the same time. In this case, it is equivalent to taking pictures regularly.
At this point in the test, we think it is necessary to figure out why the phone is cold? The mobile phones we usually use are mainly powered by lithium batteries, which mainly rely on lithium ions to move between the positive and negative electrodes to work. When charging, lithium ions come out of the positive electrode lattice through the electrolyte diaphragm to the negative electrode, and are embedded in the graphite interlayer; during working discharge, lithium ions come out from the graphite negative electrode interlayer and return to the positive electrode lattice.
In cold conditions, the electrolyte resistance increases, the ion diffusion of the positive and negative electrodes of the battery deteriorates, the lithium ion activity gradually decreases, and the battery discharge capacity becomes weak. At this time, the mobile phone is easily recognized as dead, and then automatically shuts down.
Now we go directly to the cold storage, check each mobile phone in turn, and find that all 30 mobile phones can work normally.
what happened? This does not seem to match the working principle of the found lithium battery? In order to ensure that we won’t get slapped, we used the cold storage again. This time we made the test conditions more stringent. Let the phone stand by at minus 15 degrees for 180 minutes, and go in every 30 minutes to check the situation and record the power.
I feel that among the 30 mobile phones this time, at least one or two of them cannot be carried, right? However, after checking 1, 2, 3, 4, and 5 times, they were found to be really strong. Some models did not even lose power. In the infrared thermometer screen, the iPhone’s body temperature was already It reaches about minus 10 degrees, but it can still be used to light up the screen.
Say…what about automatic shutdown? Is the experimental method wrong? None of the preset experiment results appeared. We opened the search engine again and looked for information about the phone’s winter shutdown to see if there were any omissions in the test. As a result, we found that most of these news were concentrated before 2018.
Does that mean that the situation is much less now, that is… technological advancement?
Battery technology optimized?
For this reason, we contacted several engineers and friends who are engaged in mobile phone manufacturing and battery related, and verified this conjecture.
Due to the development of fast charging technology in the past two years, the electrolyte that hinders the activity of lithium ions at low temperatures has been replaced with a high-conductivity electrolyte. The anode and cathode materials in the battery have also been optimized to improve lithium ion Charge exchange rate and lithium ion insertion rate reduce impedance and enhance activity.
The main purpose of this is to make charging faster, and the corresponding benefit is to improve the low-temperature conductivity. So here you can clearly understand that the low temperature disadvantages of lithium battery electrolyte, positive and negative electrodes in principle have been optimized a lot by the iteration of fast charging technology. Anyway, in our experimental environment, for our machine Type, minus 15 degrees is no problem.
In addition to the battery itself, an engineer friend also said that in order to ensure normal use at low temperatures, some mobile phones will also use the strategy of letting the processor run empty to increase the internal temperature and ensure battery activity.
When monitoring the temperature in our actual test, we will indeed find that some models have mysterious heat, which brings the temperature of the body that has fallen below zero to zero.
This is undoubtedly a very unexpected but reasonable way to ensure the use of extreme environments. After all, after so many years, the Snapdragon has already become a fire dragon, and it is convenient to obtain local materials.
Is it okay to charge when it’s cold?
Can we charge it directly in such an extremely cold environment? Many materials tell us that we cannot. They say that if lithium ions cannot squeeze into the cold-shrinked graphite layer in a low temperature environment, they will deposit on the surface of the negative electrode to obtain electrons and precipitate metallic lithium, which will reduce the battery performance and capacity.
But after the previous experiment, we didn’t preset the result, and went directly to the cold storage to start charging. From the final test results, a total of 5 mobile phones cannot be charged, and the rest are normal.
However, we also asked friends in the professional field. They still suggest that unless you have to, please bring your phone to normal working temperature before charging it. Mobile phones that cannot be charged also directly protect the battery from the system level. There is no difference, but an extreme use scenario is missing for the user.
OK, the above is today’s supplementary point. We feel it is necessary to emphasize again that the test results are only responsible for our test environment and the mobile phone tested.
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