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How to Determine Electric Vehicle Battery Decay

(Summary description)Problem of Electric Vehicle Battery Decay

How to Determine Electric Vehicle Battery Decay

(Summary description)Problem of Electric Vehicle Battery Decay


As is known to all, electric vehicles have been implemented in China for several years. In addition to the problem of safe endurance, the problem of battery decay is not so obvious, because under normal circumstances, the problem of battery decay will not be suddenly exposed, it will only be slowly exposed with the increase of vehicles using time. Today we're going to look at what's going on with battery decay.



At present, the battery market of electric vehicles is basically only two, the first is lithium iron phosphate battery, the second is NCM lithium battery. Of course, because the energy density of NCM lithium battery is higher than that of lithium iron phosphate battery, it is smaller under the same conditions, and it performs better at low temperature, so the utilization rate of NCN lithium battery is higher than that of lithium iron phosphate battery.


But no matter which type of lithium battery is used, they all work in the same way, based on the movement of lithium atoms in the positive and negative pole to discharge electricity. For the battery, safety is one of the problems, but this problem is a certain degree of uncertainty, then another point is the battery decay, this problem can be used to say with certainty. Because as long as you're a lithium battery, then decay is inevitable.


It's not just the lithium batteries in cars, but also in our mobile phones, computers and other devices. Take cell phones for example. When you first buy a phone, it may only take a charge a day, but after a period of time, you will find that the battery life is not as good as before. This phenomenon can be very intuitive to see the problem of lithium battery decay.


After a long period of use, it is normal for the performance of an electric vehicle battery to decline to a certain extent. At present, country stipulates that the performance of the battery appears attenuate must not exceed 20% inside shelf life, otherwise, they will be replaced free by manufacturer. However, the definition of this 20% is relatively vague, because everything should be based on the manufacturer's standards.


Attenuation of battery is mainly under the condition of the same charge, before the table show the range and there is a big gap, the range of 100% before such as power range of 350 km, and the extra charge to 100% when electricity is only 250 km, or will charge into the 20 KWH of electricity once upon a time, now only 10kwh of electricity charge, which means that the vehicle's battery attenuation has some abnormal.


In fact, this phenomenon can also be interpreted as the imbalance of cells inside the battery pack. The battery pack is composed of cells, and problems in a single cell will affect the whole battery pack. In order to protect the battery, the car will take the worst battery standard as the standard of the whole battery pack when charging, so there will be power failure, or not to 100% power directly jump to 100% phenomenon.



As for why battery decay, in short, in a lithium battery, there is a layer of exchange film through which lithium ions pass to and fro to charge and discharge. After multiple charging, a small fraction of the lithium ions become inactive and deposited, forming an electrically insulated shell inside the battery. The thicker the shell, the worse the battery's performance.

In addition, during discharge, some lithium ions will be consumed to make up for the damage of the exchange membrane. At this time, due to the decrease in the number of lithium ions, the range will be reduced. Although there is no direct solution to the attenuation of lithium battery, with the improvement of technology, there will surely be a perfect solution to the attenuation of lithium battery.



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