Application of battery management system

In today's society, energy shortages and environmental pollution have raised important issues for mankind. Battery manufacturers have actively developed various types of batteries, especially lithium-ion power batteries as advanced representatives to solve this problem. The bottleneck of the application and promotion of lithium-ion power batteries is mainly the failure of a single battery in the battery pack when used in combination, resulting in a decrease in the overall performance of the battery pack and over-limit use of the battery pack. The "Battery Pack Management System" produced by Harbin Guantuo Power Supply Co., Ltd. collects, analyzes, and makes decisions on the voltage, current, environment, and operating temperature of the series-connected single cells in the battery pack, and through the interface and charger, load controller, indicating instrument and other external equipment functions, it detects the working status of the battery pack in real time, extends the service life of the battery pack, and thus opens this bottleneck.

The battery management system has a CAN bus interface, through which the battery management system communicates with the electric vehicle main controller, and can transmit all monitoring data of the battery management system, including total current, single cell maximum voltage, single cell minimum voltage, maximum temperature, minimum temperature, SOC, total voltage, etc. The electric vehicle main controller adjusts the control of the whole vehicle in real time based on the data transmitted by the battery management system, so as to achieve a more reasonable use of the lithium power battery and extend the service life of the lithium power battery.

Main technical indicators of management system

1 The management system adopts modular design, with a total of 10 voltage acquisition modules, each of which has a temperature measurement sensor, with a total of 10 temperature measurement points. Current measurement uses independent modules, and voltage and current acquisition are managed and controlled by the host computer. Voltage and current modules use standard modules.

2 Single cell voltage sampling range 0~5V, sampling accuracy ±15mV,

Current sampling range 0~300A, sampling accuracy 1A

Temperature sampling range: -20℃ ~ 80℃, sampling accuracy: ±1℃

3 Control method

Voltage Management:

When the battery pack is working (discharging), the output is limited: when the voltage of any battery drops to 3.65V (can be set), a flashing LED alarm light will be lit, and the motor controller will be given a signal to limit the output. Stop output: when the voltage of any battery drops to 3.3V (can be set), a relay closure signal will be sent to the motor controller to control the motor to stop output. Forced disconnection: when the voltage of any battery drops to 3.0V, a red flashing LED alarm light will be lit, and a relay closure signal will be sent after a delay of 20S to control the disconnection contactor to cut off the battery discharge circuit, and the relay contact is normally open.

When the battery pack is charging, if the voltage of any battery exceeds 4.3V, a red flashing LED alarm light will light up, and the signal will be sent to the charger, which will stop charging immediately, or to the motor controller to stop energy recovery.

Temperature Management:

When the battery pack is discharged, when any temperature is detected to be greater than 40℃, a relay closure signal is issued to start the fan. When the temperature is greater than 52℃, a red flashing LED alarm light is turned on to limit the motor controller output. After the fan is started, when the temperature drops to 36℃, the fan stops.

When the battery pack is charging, if any temperature is detected to be greater than 40℃, a relay closure signal (the same relay as above) is sent to start the fan. When the temperature is greater than 52℃, a red flashing LED alarm light is lit to signal the charger to stop the charger output. After the fan is started, when the temperature drops to 36℃, the fan stops.

The LED that lights up when the temperature is greater than 52°C and the LED that lights up when the voltage exceeds 4.3V are the same.

Current Control:

When the battery pack is discharging, the discharge current is limited to 90A, and a red flashing LED warning light is lit. When it exceeds the limit, a signal is sent to the motor controller, and the motor controller limits the output. When the battery pack receives energy feedback current exceeding 30A, a red flashing LED warning light is lit, sending a signal to stop the energy feedback of the motor controller.

4. Battery management system data upload computer communication

The main control module of the management system has a USB output interface, which can realize communication with the computer. The main control module has a CAN2.0B interface, which can communicate with other devices through the CAN protocol.

Parameter adjustment of the management system can be completed by touching the buttons on the color screen.

The computer software can receive the working information of the battery pack at any time, and display and record the content including the single battery voltage, temperature, current, SOC and total voltage, and the recording format is notepad or Excel. According to the recorded data, the time/voltage (current) and voltage (time)/capacity curves can be drawn and printed.

The management module has a data storage function, which can save the last three days of data uploaded to the host computer by the battery pack at any time. The data content is the single battery voltage, charge and discharge current, temperature, and SOC value. The data on the memory can be read by the computer. The memory can be in the form of a flash memory or a memory card, and the data can be stored in the memory for a long time.

5 The main control module uses a color 5.6-inch or 4.3-inch touch LCD screen, and the data sampling time is 500ms.

The accuracy requirement of SOC is ±8%.

The management system operating voltage is DC12V, which is provided externally.

The management system consumes less than 5W of power when working and less than 25mW when not working.

Wherever lithium batteries are used, there are battery management systems. Together with green energy, battery management systems will bring new hope to our society.