What is a Battery Management System (BMS)?
A BMS is a group of electronic devices that monitor and manage all aspects of a battery's performance. Most importantly, it prevents the battery from operating outside its safe range. The BMS is critical to the safe operation, overall performance and life of the battery.
(1) A battery management system is used to monitor and protect lithium-ion battery packs.
(2) It monitors the voltage of each series-connected battery and protects the battery pack.
(3) Usually interfaces with other equipment.
Lithium battery pack management system (BMS) is mainly to improve the utilization of the battery, to prevent the battery from overcharging and over discharging. Among all the faults, compared to other systems, the failure of BMS is relatively high and difficult to deal with.
What are the common failures of BMS? What are the causes?
BMS is an important accessory of Li-ion battery pack, it has a lot of functions, Li-ion battery management system BMS as a strong guarantee of safe battery operation, so that the battery maintains a safe and controlled charging and discharging process, greatly improving the cycle life of the battery in actual use. But at the same time, it is also more prone to failure. The following are the cases summarised by BSLBATT lithium battery manufacturer.
1、The whole system does not work after the system is powered
Common reasons are abnormal power supply, short circuit or break in the wiring harness, and no voltage output from DCDC. The steps are.
(1) Check whether the external power supply to the management system is normal and whether it can reach the minimum working voltage required by the management system;
(2) See if the external power supply has a limited current setting, resulting in insufficient power supply to the management system;
(3) Check if there is a short circuit or a broken circuit in the wiring harness of the management system;
(4) If the external power supply and wiring harness are normal, check whether the DCDC of the system has voltage output, and replace the bad DCDC module if there is any abnormality.
2、BMS cannot communicate with ECU
Common reasons are that the BMU (master control module) is not working and the CAN signal line is disconnected. The steps are.
(1) Check whether the power supply 12V/24V of the BMU is normal;
(2) Check whether the CAN signal transmission line and connector are normal, and observe whether the data packet can be received.
3. Unstable communication between BMS and ECU
Common causes are poor external CAN bus matching and long bus branches. The steps are
(1) Check whether the bus matching resistance is correct;
(2) whether the matching position is correct and whether the branch is too long.
4、BMS internal communication is unstable
Common reasons are loose communication line plug, CAN alignment is not standardized, BSU address has repeated.
5、Collection module data is 0
Common reasons are disconnection of the collection line of the collection module and damage to the collection module.
6、 The battery temperature difference is too large
Common reasons are loose cooling fan plug, cooling fan failure, temperature probe damage.
7、 Can not use the charger charging
May be the charger and BMS communication is not normal, can use a replacement charger or BMS to confirm whether it is BMS fault or charger fault.
8、SOC abnormal phenomenon
SOC changes a lot during system operation, or jumps repeatedly between several values; during system charging and discharging, SOC has a large deviation; SOC keeps showing fixed values unchanged. Possible causes are incorrect calibration of current sampling, mismatch between current sensor type and host program, and battery not being charged and discharged deeply for a long time.
9、Battery current data error
Possible causes: loose Hall signal line plug, Hall sensor damage, acquisition module damage, troubleshooting steps.
(1) Unplug the current Hall sensor signal line again.
(2) Check whether the Hall sensor power supply is normal and the signal output is normal.
(3) Replace the acquisition module.
10、Battery temperature is too high or too low
Possible causes: loose cooling fan plug, cooling fan failure, temperature probe damage. Troubleshooting steps.
(1) unplug the fan plug wire again.
(2) energize the fan and check if the fan is normal.
(3) Check whether the actual temperature of the battery is too high or too low.
(4) Measure the internal resistance of the temperature probe.
11、Insulation monitoring failure
If the power cell system is deformed or leaking, an insulation failure will occur. If the BMS is not detected, this may lead to electric shock. Therefore, BMS systems have the highest requirements for monitoring sensors. Avoiding the failure of the monitoring system can greatly improve the safety of the power battery.
BMS failure five analysis methods
1、Observation method: when the system occurs communication interruption or control abnormalities, observe whether there are alarms in each module of the system, whether there are alarm icons on the display, and then for the resulting phenomenon one by one to investigate. In the case of conditions permitting, as far as possible under the same conditions to let the fault recurrence, the problem point to confirm.
2、Exclusion method: When a similar disturbance occurs in the system, each component in the system should be removed one by one to determine which part is affecting the system.
3、Replacement method: When a module has abnormal temperature, voltage, control, etc., swap the module position with the same number of strings to diagnose whether it is a module problem or a wiring harness problem.
4、Environmental inspection method: when the system fails, such as the system can not be displayed, often we will ignore some details of the problem. First we should look at the obvious things: such as whether the power is on? Has the switch been turned on? Are all the wires connected? Perhaps the root of the problem lies within.
5、Program upgrade method: when the new program burned after an unknown fault, resulting in abnormal system control, you can burn the previous version of the program for comparison, to analyze and deal with the fault.
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