Power lithium-ion battery management system Lithium - Ion Battery Equipment

Power lithium-ion battery management system (BMS) - Lithium - Ion Battery Equipment

The biggest difference between new energy vehicles and traditional vehicles is that they use batteries as power drives, so the technology of power lithium batteries is the core of new energy vehicles.

What is the core technology of BMS?

Recently, I saw a propaganda board of a domestic company, claiming to fully master BMS software and hardware technology, reaching the world's advanced level, and adopting multiple balanced control capabilities because of the use of the underlying software such as AUTOSAR's software architecture. Very eye-catching. Are these things the core technology of BMS?

Usually the BMS system usually includes a detection module and an operation control module.
Detection refers to measuring the voltage, current and temperature of the cell and the voltage of the battery pack, and then transmitting these signals to the operation module for processing and issuing instructions. So the operation control module is the brain of the BMS. The control module generally includes hardware, basic software, runtime environment (RTE) and application software. The core part of the application software. About the environment developed with Simulink is generally divided into two parts: battery state estimation algorithm and fault diagnosis and protection. State estimation includes SOC (StateOfCharge), SOP (StateOfPower), SOH (StateofHealth), as well as equalization and thermal management.(Lithium - Ion Battery Equipment)

, BMS original hotspot of electric vehicle power lithium battery management system

Battery state estimation usually estimates SOC, SOP and SOH. SOC (state of charge) is simply how much electricity is left in the battery; SOC is the most important parameter in BMS, because everything else is based on SOC, so its accuracy and robustness (also called error correction) ability) is extremely important. If there is no accurate SOC, no amount of protection functions can make the BMS work normally, because the battery will always be in a protected state, and it will not be able to prolong the life of the battery.

In addition, the estimation accuracy of SOC is also very important. The higher the accuracy, the higher the cruising range for the same capacity battery. Therefore, high-precision SOC estimation can effectively reduce the required battery cost. For example, Chrysler's Fiat 500eBEV can always discharge SOC=5%. It became the longest-range electric car at the time.

SOP is the maximum discharge and charged power that the battery can supply at the next moment, such as the next 2 seconds, 10 seconds, 30 seconds and continuous high current. Of course, the effect of continuous high current on the fuse should also be considered here.

Accurate estimation of SOP can maximize the utilization efficiency of the battery. For example, when braking, you can absorb as much feedback energy as possible without harming the battery. When accelerating, more power can be supplied for greater acceleration without harming the battery. At the same time, it can also ensure that the car will not lose power due to undervoltage or overcurrent protection during driving even when the SOC is very low. In this way, the so-called primary protection and secondary protection are fleeting in the face of precise SOP. That's not to say protection isn't important. Protection is always necessary. But it cannot be the core technology of BMS. Accurate SOP estimation is especially important for low temperature, old batteries, and very low SOC. For example, for a group of well-balanced battery packs, when the SOC is relatively high, the SOC may differ from each other by a small amount, such as 1-2%. However, when the SOC is very low, there will be a rapid drop in the voltage of a certain cell. The voltage of this cell is even more than 1V lower than other batteries. To ensure that the voltage of each cell is never lower than the minimum voltage given by the battery supplier, the SOP must accurately estimate the maximum output power of the cell whose voltage drops rapidly at the next moment to limit the use of the battery and protect the battery. The core of estimating SOP is to estimate each equivalent impedance of the battery online in real time.



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