Electric vehicles will use lithium batteries as the main power source in the future, mainly because lithium batteries have the advantage of high energy density, so their performance is relatively stable. However, the quality of lithium batteries is not easy to grasp when mass-produced, and there is a slight difference in the power of the battery cells when they leave the factory, and with the operating environment, aging and other factors, the inconsistency between batteries will become more and more obvious, and the battery efficiency and life will also deteriorate. In addition, overcharging or overdischarging may lead to safety problems such as fire and combustion in severe cases.

The importance of battery management system BMS is self-evident. BMS is the core technology of power battery packs, and it is also the most concerned part of vehicle enterprises. The following Shenzhen Haoqixin analysis: TI and ST‘s electric vehicle BMS solution.

1. ADI fully isolated lithium-ion battery monitoring and protection system

Solution Features: Lithium-ion battery packs contain a large number of battery cells, which must be properly monitored to improve battery efficiency and prolong battery life to ensure safety. The 6-channel AD7280A device in the scheme acts as the primary monitor, providing accurate voltage measurements to the system demonstration platform evaluation board, while the 6-channel AD8280 device acts as the secondary monitor and protection system.

The AD8280 is a pure hardwired safety monitor for Li-Ion battery packs that, when used with the AD7280A, provides a low-cost, redundant, backup battery monitor with adjustable threshold detection and shared or separate alarm outputs. It has a self-test function, making it suitable for high-reliability applications such as hybrid electric vehicles or high-voltage industrial applications such as uninterruptible power supplies. Both the AD7280A and AD8280 derive their power from the monitored battery cells.

The ADuM5404 integrates a DC-DC converter to power the high voltage side of the ADuM1201 and ADuM1401 isolators, and to provide VDRIVE power to the AD7280 ASPI interface. These 4-channel, magnetically isolated circuits are a safe, reliable, and easy-to-use optocoupler replacement solution.

2. TI launched battery active load balancing technology

Scheme features: Active balancing method recommended for electric vehicles: Each battery cell controls the combination of the transformer and the charging circuit through the matrix switch to form a function of a voltage/current reservoir with adjustment function. The inconsistency after charging and discharging leads to the decrease of the charging and discharging capacity of the whole group of batteries. It can be adjusted by the circuit connecting the back end to the storage battery. During charging, it will not stop charging and discharge because the internal pressure of a certain battery cell is too high. It can also release 100% of the energy completely, thereby extending the driving distance of the electric vehicle.

The energy conversion efficiency of the isolated DC-DC active equalization technology is as high as 87%. For example, the EM1410 chipset consists of 5 core chips and 5 power supply chips. The most important EMB1432 is a fourteen-channel AFE chip, EMB1428 is a seven-channel gate controller chip, and EMB1499 is a seven-channel voltage control chip. To construct a 14-channel bidirectional active battery cell balancing function, 14 battery cells are connected in series with a maximum operating voltage of 60V, providing 5V bidirectional balancing voltage and a maximum stack output voltage capability of 750V, and meeting the AECQ-100 automotive electronics verification standard.

The above is the analysis of the electric vehicle BMS solutions of TI and ST. With the high-end development of new energy vehicle products, the requirements for BMS are getting higher and higher, and the active balance technology will succeed in the future development trend.