First, let’s introduce what the three electric systems on pure electric vehicles are. The three-power system is divided into three modules: battery, motor and PMS. PMS, the full name is PowerManagementSystem, literally translated as energy management system. In fact, the real purpose of the PMS system is to provide unified management of the entire three-power system. However, the two major modules that PMS has to manage are a motor and a battery. There is nothing to control about the motor. It is nothing more than energizing, controlling the frequency converter, and changing simple parameters such as current. A small microcontroller can handle this, and there is no need for PMS. Take action. What PMS really wants to take care of is the battery pack.

　　Low temperature lithium iron phosphate battery 3.2V 20A -20℃ charging, -40℃ 3C discharge capacity ≥70%

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　　Before talking about PMS, we must first understand some characteristics of the battery pack. Now, whether it is the cylindrical 18650 battery cells used by Tesla or the package batteries used by other manufacturers, they are essentially lithium-ion batteries, no different from the ones in your mobile phone. The lithium-ion battery itself is a very flammable and explosive dangerous item. It can easily burst into flames and explode. So why does this happen?

　　Let’s start with the most basic principles. The structure of the battery is actually very simple. The positive and negative electrodes contain some lithium ions with positive polarity. There is a film between the positive and negative electrodes. This film is called SEI film. , there is also a layer of electrolyte next to the SEI membrane (when a common battery hangs up, the water that flows out is the electrolyte).

　　The working principle is also very simple. Lithium ions, just like us, also have a home. Their home is the positive electrode, but staying at home cannot create value and build a new era of socialism, so it needs to be charged. Charging is to remove the lithium ions from the battery. Drive them out of their homes and force them to go to the company (negative electrode). When all the lithium ions are put to work, then the battery will be considered fully charged.

　　But just like everyone rushes home after work, lithium ions also rush back to their homes after work. This is discharge, because the ions are really homesick, and discharge is usually accompanied by a large energy release. , which is why batteries can supply energy.

　　But just like people, when the weather is too cold, a considerable part of the lithium ions will become lazy and unwilling to move when they stay at home or in the company. At the same time, the weather is cold, just like the current cold winter in the industry, the company has to reduce its scale. Originally A company that can seat 100 lithium ions can only seat 50 people now because it is too cold. What about the remaining 50 people? I can only go home. This is why lithium-ion batteries run out of power in winter. So what if the weather is too hot? Just as we humans get angry easily in summer, so do lithium ions. Therefore, if the temperature is too high, the battery will easily burn.

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