1. Classification of electric vehicle batteries
Energy crisis and environmental pollution are the two major problems facing countries in the world today. Electric vehicles have become the inevitable trend of future automobile development due to their advantages of energy saving and environmental protection. Electric vehicle batteries are the main power source of electric vehicles, accounting for 30% to 50% of the cost of electric vehicles. Electric vehicle batteries can be divided into two categories, namely storage batteries and fuel cells. Batteries are suitable for pure electric vehicles and can be classified as lead-acid batteries, nickel-based batteries (nickel-hydrogen batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-zinc batteries), sodium-sulfur batteries, sodium-chlorine batteries Nickel batteries, secondary lithium batteries, air batteries and other types. Fuel cells are dedicated to fuel cell electric vehicles and can be divided into alkaline fuel cells (AFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), and proton exchange membranes. Fuel cell (PEMFC), direct methanol fuel cell (DMFC) and other types.
2. The role of electric vehicle batteries
In pure electric vehicles, the electric vehicle battery is the only power source for the vehicle drive system. In a hybrid vehicle, the battery is the main power source of the vehicle drive system at low speed and when it is started; when accelerating at full load, the battery is the auxiliary power source of the vehicle drive system; during normal driving, deceleration, and braking, the battery acts as an auxiliary power source. The role of energy storage. 3. Electric vehicle battery management system Electric vehicle batteries are a technical bottleneck restricting the scale development of electric vehicles and a key factor in the high price of electric vehicles. The performance of the electric vehicle battery management system (BMS) largely determines the cost, energy saving and safety of electric vehicles. BMS monitors the battery voltage, charge and discharge current and battery pack temperature, can estimate the remaining battery percentage (SOC) of the battery, control battery charge and discharge balance, conduct thermal management of the battery pack, and carry out CAN communication with the on-board monitoring system and charger. Realize coordinated control and optimized charging, keep the battery in the best working condition, give full play to the function of the battery, and prolong the service life of the battery. The main functions of BMS include: voltage, current, and temperature detection; SOC estimation; charge and discharge control; balance control; thermal management; safety management and CAN communication, etc. Accurate measurement of voltage and current of battery packs and single cells is the prerequisite for battery SOC estimation, charge and discharge control, balance control and safety management. Different battery packs have different charging voltages and currents. The charging currents of the same electromagnetic group or single battery at different stages are very different. The voltage and current test sensors and meters are required to maintain the necessary accuracy within a wide dynamic range, which is the BMS power. One of the technical difficulties of testing. SP series variable frequency power sensors have high-precision testing capabilities within a wide dynamic range, and are particularly suitable for voltage and current testing of electric vehicle battery management systems and charging test systems.
