BMS failures are relatively high and difficult to handle among all failures compared to other systems.

The battery management system BMS (Battery Management System) is responsible for controlling the charging and discharging of the battery and implementing functions such as battery state estimation and is closely related to the battery and the vehicle system.

However, many domestic auto manufacturers and battery pack companies have insufficient understanding of the importance of BMS. Some car companies even believe that by linking each single battery cell, the vehicle's operation can be guaranteed, and their safety is a fluke.

It is reported that some car companies (take low-speed cars as an example) blindly pursue low prices in BMS procurement to seize market share. Some bad BMS suppliers reduce BMS functional indicators or "castrate" some functions to achieve low-cost results to obtain contracts.

But, among all the failures, the failure of BMS is relatively high and difficult to handle compared with other systems. Such irresponsibility has caused damage to the healthy development of the industry while laying down security risks.

Therefore, the starting point lithium battery big data reporter has sorted out the types of common faults of BMS for reference in the industry.

1. The main relay does not pull in after power-on

possible reason:

The load detection line is not connected, the precharge relay is open, and the precharge resistor is open.

troubleshooting:

Use the BDU display module to check the bus voltage data, check the battery bus voltage and whether the load bus voltage is standard; check whether the load bus voltage rises during the precharge process.

2. The BMS cannot communicate with the ECU

possible reason:

BMU (central control module) does not work, CAN signal line is disconnected

troubleshooting:

Check whether the 12V/24V power supply of the BMU is standard; check whether the CAN signal transmission line is out of pin or the plug is not inserted; monitor the CAN port data, whether it can receive BMS or ECU data packets.

3. The communication between BMS and ECU is unstable

possible reason:

Poor matching of external CAN bus, too long bus branch

troubleshooting

Check whether the bus matching resistance is correct, whether the matching position is correct and whether the branch is too long.

4. Internal communication of BMS is unstable

possible reason:

The plug of the communication cable is loose, the CAN wiring is not standardized, and the BSU address is repeated.

troubleshooting:

Check whether the wiring is loose; check whether the bus matching resistance is correct, whether the matching position is correct, and whether the branch is too long; check whether the BSU address is repeated.

5. After the system is powered on, the whole system does not work

possible reason:

Abnormal power supply, wiring harness short circuit or open circuit, DCDC no voltage output.

troubleshooting:

Check whether the external power supply supplies power to the management system usually and whether it can reach the minimum operating voltage required by the management system, and see if the external power supply is limited in the current setting, resulting in insufficient power supply to the management system; you can adjust the external power supply to meet the needs of the management system. Electrical requirements; check whether the wiring harness of the management system is short-circuited or open-circuited, and modify the wiring harness to make it work usually; if the external power supply and wiring harness are standard, check whether the DCDC in the management system that supplies power to the entire system has voltage output; if so Abnormal can replace the bad DCDC module.

6. The battery current data is wrong

possible reason:

The plug of the Hall signal line is loose, the Hall sensor is damaged or reversed, and the acquisition module is damaged.

troubleshooting:

Re-plug the current Hall sensor signal line; check whether the Hall sensor power supply is standard and whether the signal output is average; replace the acquisition module.

7. The battery temperature difference is too large

possible reason:

The cooling fan plug is loose, the cooling fan is faulty, the coolant fails, and the cold zone system does not start.

troubleshooting:

Re-plug the fan plug cable; supply power to the fan alone, check whether the fan is standard, replace the coolant, and check the cooling system.

8. The system reports an error after the relay operates

possible reason:

The auxiliary relay contact is disconnected, and the relay contact is stuck.

troubleshooting:

Re-plug the wiring harness; use a multimeter to measure whether the on-off state of the auxiliary contact is correct. Check the cause of the fusing error and replace the relay after eliminating the cause.

9, can not use the charger to charge

possible reason:

The communication between the charger and the BMS is abnormal.

troubleshooting:

Replace a charger or BMS to confirm whether it is the BMS fault or the charger fault; check whether the matching resistance of the BMS charging port is normal.

10. The vehicle instrument has no BMS data display

possible reason:

Abnormal connection of the main control module wiring harness

troubleshooting:

Check whether the wiring harness of the main control module is fully connected, whether there is an average low-voltage working voltage of the car, and whether the module is usually working.

11. The detection data of some battery boxes are lost

possible reason:

Some connectors of the whole vehicle may be in poor contact, or the BMS slave control module may not work correctly.

troubleshooting:

Check the contact of the connector, or replace the BMS module.

12. Abnormal SOC

Phenomenon: SOC varies greatly during system operation or repeatedly jumps between several values; during system charging and discharging, SOC has a significant deviation; SOC has always displayed a fixed value.

possible reason:

The current is not calibrated; the current sensor model does not match the host program; the battery has not been intensely charged and discharged for a long time; the data acquisition module jumps in the acquisition, causing the SOC to perform automatic calibration; the Hall sensor is faulty;

Two conditions for SOC calibration: 1) Overcharge protection is achieved; 2) The average voltage is above xxV. The customer's battery has poor consistency, and the second condition cannot be reached when it is overcharged. Check the remaining capacity and total capacity of the battery through the display; if the current sensor is not connected correctly;

troubleshooting:

Calibrate the current in the touch screen configuration page; change the host program or replace the current sensor;

Perform a battery's deep charge and discharge, replace the data acquisition module, and manually calibrate the system SOC. It is recommended that the customer do a deep charge and discharge once a week; modify the host program, and adjust the "average voltage above xxV" according to the customer's current situation. xxV. Set the correct total battery capacity and remaining capacity; connect the current sensor correctly to make it work properly.

Summarize:

It is reported that BMS is an indispensable and vital component in power and energy storage battery packs. With the development of the new energy industry chain, the technology and market scale of BMS are proliferating.

In terms of technology, starting point research (SPIR) statistics show that in 2017, the cost of BMS accounted for an average of 20% of the total cost of the battery pack.

Relevant personnel of a management system manufacturer said that there used to be insulation detection alarms, and the data of the acquisition module was 0, but now it rarely occurs.

With the rapid development of BMS technology, there are no alarms related to insulation detection. At the same time, it is rarely seen that the data of the acquisition module is 0.

Starting Point Research (SPIR) predicts that the compound annual growth rate of the BMS market brought by global new energy vehicles will reach about 30% from 2018 to 2025.

It can be seen that the market development is uneven, except for some excellent and unhealthy phenomena, the technology development of BMS has made a qualitative leap compared with the market size before, and it has continued to improve.