Charging lithium battery safety is not to say!

Charging lithium battery safety is not to say!

In recent years, there have been many electric vehicles’ exposure to fire, making people pay more and more attention to electric vehicles, especially lithium-ion batteries.. Of course, this is not that the safety of electric cars is very poor.

The ordinary gasoline cart is also prone to fire events, especially in summer, as long as you pay attention, you will find that the spontaneous combustion event of the gasoline car is not a small number, but we also hope to be able to be from lithium-ion batteries. Safety design prevents similar accidents, after all, people’s security is greater than everything, just as the “people are the scale of people”. At present, our judgment of lithium-ion battery safety has also stayed in a more primary stage, and the judgment standard is relatively blurred, and only several obvious points of the risk level of the battery, but in fact, the lithium-ion battery is transformed from full safety state to complete The dangerous state is a continuous change curve, that is, the current judgment system cannot judge the battery safety status between the two states, which forms a battery-safe state of the blind spot, so the security judges for lithium-ion batteries Chemical, digitization is particularly important, especially about the application of power lithium batteries in electric vehicles.

. Currently, standards for lithium-ion battery safety are classified for the hazard grade developed by the European Automobile Research and Development Council..

The hazard level classification table divides the battery risk level into 0-7 eight levels, the higher the level, the more dangerous. For example, the 6th level indicates that the battery has a fire but has not exploded, and the highest level 7 indicates that the battery not only happens, but also a dangerous explosion..

In order to ensure the safety of the operator, it is necessary to control the hazard level within 4, that is, the battery does not rupture, fire and explosion.. First we have to establish a concept, security and abuse are relatively, adding abuse strength, necessarily reducing the safety of battery systems.

. At present, most of the safety description of lithium-ion battery is based on the summary of relevant experience, lack of accurate description of digital properties..

In order to digitize battery risk, Ashtiani invented risk mode and risk analysis (HMRMA) model, the model is important to compose risk severity HS and risk probability HL. Among them, the HS value is 0-7 represents the severity of the risk, the HL value is 1-10 indicates the possibility of risk, representing the number of risks per 1 million samples. In order to reduce the value of the risk HR, you can choose to reduce HS or HL, or we can also introduce a new variable risk control HC, so the above formula can be transformed into, where the value of HC is 0-1, completely does not control HC 1, complete control, HC is 0.

The risk of the battery As the battery is constantly changing, in order to reflect this change, the LU or the like is based on battery voltage and use temperature, and the functional status function SOF is introduced, the function is important There is battery charge state SOC and battery safety status SOH, and the output power of the battery. Where P (t) is the instantaneous power of the battery output, the PD is the instantaneous demand power, and the PMax is the maximum output power when the battery is a new state..

Where P (t) = pMax ¡¤ SOC (T) ¡¤ SOH (T) where SOH (t) can be determined based on the value of the voltage, as shown in the following formula, where V (t) is an instantaneous output voltage, and VD is the minimum demand for load. Voltage, VLIM is equipped with load minimum output voltage when the battery is new..

The system can perform good linear relationship between lead-acid battery SOC and voltage on the lead-acid battery, but is not a complete linear relationship between the lithium ion battery SOC and the voltage, so appropriate corrections. The content of this article has introduced some current scholars’ research results for lithium-ion battery safety models. The following tablets will be combined with the safety experimental data of 18650 batteries, introduce and use battery safety model method.

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