Why do power lithium batteries need a battery management system

Why do power lithium batteries need a battery management system? Currently, new energy cars are classified into three categories: hybrid electric vehicles (HEV), fuel cell electric vehicles (FCEV), and pure electric vehicles (EV). These three kinds of electric cars have distinct features and are in various phases of development owing to their diverse constructions and operating principles.

Pure electric cars rely only on on-board power battery packs (such as lithium-ion batteries, lead-acid batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, among others) and are powered by high-power motors. Thus, it differs from conventional internal combustion engine automobiles.

The most notable distinction is the electric propulsion and control system seen only in fully electric cars. Pure electric cars feature lower noise levels, no pollution, zero emissions, and a simpler chassis construction than hybrid electric vehicles; in comparison to fuel-powered cell vehicles, all areas of technology are more mature, with superior dependability and safety. As a result, governments and automakers all over the globe place a high importance on pure electric cars, and several businesses have completed batch production and begun demonstration operations in certain places.

In pure electric cars, the power lithium battery pack, as one of the essential components, accounts for a significant amount of the total manufacturing cost, and its performance has a direct impact on the overall driving performance and safety of the vehicle. The majority of the power lithium batteries used in early pure electric cars were lead-acid batteries.

Due to their poor energy density, limited cruising range, and short service life, these batteries were progressively replaced by technologies such as lithium-ion batteries, which provide significant improvements. Lithium-ion batteries have gained the interest and utilization of many electric car manufacturers both domestically and internationally owing to its advantages such as high charging and discharging efficiency, high energy density, and long durability.

Although lithium-ion batteries offer more benefits than previous kinds of batteries, they are nevertheless constrained by cell materials and current production procedures, resulting in variations in internal resistance, capacity, and voltage between single-cell lithium-ion batteries. As a result, in real operation, the individual cells inside the battery pack are prone to uneven heat dissipation or excessive charge and discharge. Over time, these batteries under poor operating conditions are likely to be destroyed, reducing the total life of the battery pack.

Not only that, but the battery is severely overcharged, and there is a risk of explosion, which would destroy the battery pack and endanger the user’s life. Therefore, it is necessary to equip the power lithium battery pack on the electric vehicle with a set of targeted battery management system (Battery Management System, BMS), in order to effectively monitor, protect, balance the energy, and alarm the failure of the battery pack, thereby improving the overall power lithium battery. The battery pack’s performance and service life.

As the monitoring and management center for pure electric vehicle power lithium battery packs, the battery management system must monitor the battery pack’s temperature, voltage, charge and discharge current, and other related parameters in real time and dynamically, as well as take the initiative to take emergency measures to protect each individual battery as needed. Be aware of the risks of overcharging, overdischarging, overheating, and short circuiting the battery pack.

Furthermore, the system must accurately estimate the SOC of the battery throughout the battery pack’s life cycle and timely feed back key information such as remaining power, driving range, and abnormal faults to the driver in a suitable and simultaneous manner. An acceptable method for completing the data exchange function between the system and the car ECU or host computer.

However, these are the functions and performances that BMS can only provide under optimum design and operating circumstances. Currently, all electric vehicle incidents involving power lithium batteries or the actual usage of BMS devices in autos are considered as a whole. The performance demonstrates that the functions of the widely used battery management system are not ideal, the technology is not mature enough, the scope of application is restricted, and the variety is insufficient. The details may be summarized into the following five aspects:

Long-term usage of the power lithium battery pack might lead to inaccurate data collection by the battery management system.
The battery management system cannot accurately estimate the SOC value of a power lithium battery pack during its entire life cycle.
The energy balance between individual cells in the battery pack requires further improvement.
The battery management system’s self-diagnosis and maintenance features for the battery pack are not ideal.
Current battery management system devices have a restricted scope of application and lack mobility and adaptability.