Battery Management System 

TEAM

Mae Tran, Uditi Gupta

MOTIVATION

Electrical vehicles need a huge number of battery cells to provide energy required for vehicles’ operations. However, it is necessary to control these batteries to keep them operate safely and efficiently.  BMS is crucial for monitoring and managing the battery cell’s voltage, temperature, and current.

DESCRIPTION

This BMS is designed to monitor a pack of 3 - 18650 lithium-ion batteries connected in series, using a microcontroller ESP32 and the Battery Monitor IC LTC6811.  As of now, the BMS has two main features: reading temperature and cell voltages for each battery cell connected. In the future, the PCB can be modified to include additional features like balancing cells and can even be expanded to monitor up to 12 cells connected in series. 

FEATURES 

Compute 

• Used ESP32 Micro-Controller to communicate with the LTC6811 IC through MISO, MOSI, CS and CLK pins. 

• Used USB connection to upload the firmware

Sensing 

Temperature Reading: 

• Used a thermistor, connected in series with a fixed resistor, to form a voltage divider. 

• Using MUX4638EUE, connected the three outputs of the voltage divider to the single GPIO pin on the LTC 6811 chip (used as an ADC). Through communication from the IC, the MUX can be signalled to switch between the three sensors to provide a reading of each cell. 

Voltage Reading: 

• Connected batteries directly to pins C0, C1, C2, C3 on the  LTC6811 IC.

Power

• 1st Converter: LTC 3970EMS, Converting 12V to 5V to power the LTC6811 IC and the MUX4638EUE

• 2nd Converter: LM3940IMP, Converting 5V to 3.3V to power the ESP32 Micro-Controller

SCHEMATIC

BILL OF MATERIALS (BOM)

FRONT LAYOUT

BACK LAYOUT

3D LAYOUT

NEXT STEPS

Next Steps

• Add functionality to balance the cells

• Expand circuit to monitor more than 3 cells

• Include more sensors to get more data on the batteries

• Create a user interface for all the incoming data