| Lei
For electric vehicle owners or potential customers who are excited about electric vehicles, the most feared thing may be the news that one day accidentally brushes a car that spontaneously combusts and explodes.
In real life, as long as it is negative news about new energy vehicles, 90% of it is also related to batteries.
Why does the battery explode? Collided? The temperature is too high? In fact, these are the reasons. However, many people attribute the battery explosion to "thermal management." It is believed that the thermal management technology is not good enough, and the battery temperature is too high to be handled in time or improperly handled, which leads to the explosion of the vehicle.
But in fact, it is the BMS (Battery Management System) that determines the effectiveness of thermal management. Simply put, you can think of BMS as the "boss" of thermal management. In addition to the battery quality itself, BMS is the key to determining whether the battery of an electric vehicle is safe or not.
Thermal runaway and electrical runaway
First of all, from the perspective of causes, the explosion of the battery can basically be attributed to the following two kinds of runaway: thermal runaway and electrical runaway.
Thermal runaway is mainly due to the generation of a large amount of heat after the internal short circuit of the battery, resulting in a continuous increase in the internal temperature of the battery, resulting in battery rupture, spontaneous combustion, and explosion. For example, the spontaneous combustion of Tesla Model S in the shanghai underground garage was due to thermal runaway. After all kinds of electric vehicles are hit, if the battery is punctured, it will also cause the battery to be short-circuited, causing the battery to short-circuit and ignite and explode.
The electrical runaway is mainly caused by human reasons. In the case where the battery has been fully charged, if the circuit control system does not end the charging process or slow down the charging speed, then the battery will be overcharged, resulting in a loss of power.
Whether thermal or electrically out of control, properly designing a battery management system (BMS) is critical to preventing battery explosions.
The "brain" of the battery
If the battery is bone and muscle, then the BMS is the brain and nerves, which manage every aspect of the battery. BMS mainly includes sensors, controllers, drive switches, information and communication storage modules, etc., its core function is that according to different situations, the battery charge and discharge process can be monitored, controlled and optimized, under the premise of ensuring safety, maximize the use of energy stored in the battery.
Usually, BMS includes five parts: condition monitoring and analysis, safety management, energy management, and information management. First, the BMS will monitor and analyze the battery status; second, after the analysis is completed, the BMS will carry out energy management on the basis of determining the safety of the battery state; and finally, the BMS will store the past information for troubleshooting after the failure, or optimize the user experience.
And these modules are layered and progressive relationships.
BMS and thermal management
The temperature of the battery is too high or too low, which will cause the attenuation of the battery performance. In order to keep the battery in the best condition at all times, thermal management requires temperature management of the battery system by cooling and heating.
The cooling scheme of the battery is actually the level of hardware design, but for example, water cooling, involving specific pumps, fan actions, BMS is required to initiate a request.
For example, Volkswagen's MEB pure electric platform, its BMS can be based on the current actual working conditions to put forward requirements, in the thermal balance performance of the single battery, Volkswagen MEB can do all the cell temperature to maintain within the difference of 2 ° C before and after.
In response to the problem of failure, MEB through the four-cell safety design, from the shell strength, surface insulation, timely power failure, explosion-proof pressure relief on the quadruple insurance, the possibility of leakage, fire, explosion to the minimum, the implementation strategy of these designs, are in the BMS.
Write at the end
To put it simply, a good BMS can alert you when the battery is about to fail and be dangerous, and make corresponding precautions, which is what we often call "prevention before it happens". Therefore, many spontaneous combustion explosion of electric vehicles, perhaps not its battery quality is not good, but its BMS technology is not in place.