High-voltage power-off management: During the normal power-off process, when the driver's normal power-off instruction is detected, VCU sends the power-off instruction, and BMS successively disconnects the positive and negative relays of the high-voltage circuit after receiving the instruction. It is necessary to consider the size of the working current, speed and other vehicle status information. Emergency down high pressure, when the vehicle has a serious fault, such as collision failure, BMS should immediately down high pressure, cut off the power output.

Charge management

According to the battery temperature and SOC, the BMS looks up the charging power MAP of the battery system to determine the current maximum allowable charging current of the system. During charging, BMS interacts with charging devices (charging piles or on-board chargers) with information such as maximum voltage, maximum total voltage, maximum temperature, maximum allowable charging current, nominal energy, SOC and current battery voltage of the battery system, so that the battery system can be charged according to the appropriate charging voltage, charging current and charging method. The charging information is displayed on the meter. At the same time, the remaining charging time is estimated according to the charging current and battery SOC.

Charging technology is divided into: slow charge, fast charge, wireless charging, appointment charging, power replacement and other ways of replenishment.

Slow charge: It mainly involves BMS, VCU, OBC, PDU, instrument and other controllers.OBC detects CC and CP, interacts with the slow charging pile, and converts AC into DC, BMS controls the charging process, VCU decides whether to enable or disable the charging, PDU performs the control of the slow charging relay, and the meter displays the charging SOC, charging current, charging time, charging prompt information, etc.

Fast charge: Mainly by BMS, VCU, PDU, instrument and other controllers participate.The BMS interacts with the fast charging pile, the VCU decides whether to enable or disable charging, the PDU performs the control of the slow charging relay, and the meter displays the charging SOC, charging current, charging time, charging prompt information, etc.

Wireless charging: Mainly by BMS, VCU, wireless charging controller, PDU, meter and other controllers participate. Similar to the way of slow charging.

Reservation charging: Mainly by APP, large screen, BMS, VCU, OBC, PDU, Tbox, GW, instrument and other controllers participate, to achieve two ways of reservation charging remote reservation and local reservation, general car companies will only achieve one. Remote reservation: You can make an appointment for charging time and charging capacity. The implementation method is as follows: when the user makes an appointment for the charging function at the APP side, the request information is sent to the TSP platform, which sends the request information to the Tbox at the car side, and the Tbox at the car side stores the request information, and when the time reaches, the Tbox sends the request information to the corresponding network segment through GW to wake up the vehicle network segment. Local reservation: The user sets the charging information through the large screen, forwards the request information to the Tbox at the end of the vehicle through the instrument, and sends the request information to the corresponding network segment through GW after the time is up, and wakes up the vehicle network segment.

Battery state estimation

SOC: Mainly through ampere-hour integration method and Kalman filter algorithm, combined with correction strategies (open circuit voltage static correction (long standing), full charge correction, full discharge correction (5%-95%SOC corresponding to 0-100% display SOC), dynamic correction (look up soc and actual soc correction in the table), capacity correction under different temperatures and SOH, etc.), Estimate the remaining capacity of the battery.

SOH: The BMS can look up the table to obtain the attenuation coefficient according to the mileage and vehicle running time, and the ratio of the theoretical and actual charged capacity when the SOC can be charged by small current;

SOE: The BMS obtains the available charge and discharge power SOE of the battery by looking up the table of temperature and SOC, and considers the transfer of peak charge and discharge power to continuous charge and discharge power;

High voltage interlock monitoring

BMS monitors the high-voltage interlock failure of the battery connector. When the high-voltage interlock failure occurs, it considers the running state of the vehicle (fast running/stationary/charging state), and carries out alarm, power limiting and low-voltage treatment. Or report the fault to the VCU for decision making.

Insulation monitoring

BMS monitors the insulation failure of the battery system. When the insulation failure occurs, it considers the running state of the vehicle (normal running state/stationary state/charging state), and carries out alarm, power limit and low voltage treatment. Or report the fault to the VCU for decision making.

Collision monitoring

BMS monitors the vehicle collision failure, and carries out emergency down pressure treatment when the collision failure occurs.

Thermal management

Thermal management during fast and slow charging process: when the minimum battery temperature is too low, close the charging relay and heating relay, start the heating system, when the minimum battery temperature is greater than the normal threshold, disconnect the heating relay, resume normal charging, and stop heating when the temperature difference is too large during the heating process;

Thermal management before and during driving: control the battery temperature. When the battery temperature is too high, turn on the water pump and cooling fan to cool the battery. When the battery temperature is low, turn on the battery PTC for heating.

Battery balance management

When the threshold of the maximum and minimum SOC is greater than a certain value, determine whether to enable the balance based on conditions such as the working current, PCB temperature, SOC value, and vehicle status, and calculate the balance time based on the designed balance current.

Battery failure analysis and online alarm

Occurrence criteria: (1) The minimum cell voltage is lower than a certain threshold for a period of time.

(2) The maximum battery temperature is greater than a certain threshold.

(3) The monomer temperature rise rate is greater than a certain threshold.

(4) The temperature difference between the highest temperature and the lowest temperature is greater than a certain threshold.

If any two of the above conditions are established at the same time, the thermal runaway fault marker is immediately placed, and a signal is sent to the car end to remind the driver. Once the thermal runaway fault is triggered, the corresponding action of the fault is executed without delay, and the power output of the vehicle will be cut off immediately.

It will also send an alarm signal to the cloud, and the background will monitor the status of the vehicle and carry out subsequent rescue measures.