Battery management systems (BMS) – MCQs – EE

1. The main function of a Battery Management System (BMS) is to:
(A) Control motor speed
(B) Monitor, protect, and optimize battery performance
(C) Charge the battery faster
(D) Reduce vehicle weight

2. The BMS ensures battery safety by:
(A) Increasing voltage continuously
(B) Preventing overcharge and over-discharge
(C) Disabling cooling systems
(D) Decreasing charging current always

3. The BMS measures the following battery parameters:
(A) Temperature, voltage, and current
(B) Air pressure and humidity
(C) Tire pressure and load
(D) Rotor speed and torque

4. SOC in BMS stands for:
(A) State of Cooling
(B) State of Current
(C) State of Charge
(D) System of Cells

5. SOH in BMS stands for:
(A) State of Heat
(B) State of Health
(C) System of Hardware
(D) Source of Hydrogen

6. The State of Charge (SOC) of a battery indicates:
(A) Remaining energy capacity
(B) Battery temperature
(C) Voltage drop per cell
(D) Lifetime of battery

7. Cell balancing in a BMS is done to:
(A) Equalize voltage across all cells
(B) Increase total voltage
(C) Decrease battery current
(D) Reduce SOC

8. Passive cell balancing dissipates extra energy as:
(A) Heat through resistors
(B) Light
(C) Magnetic field
(D) Sound

9. Active cell balancing redistributes energy by:
(A) Burning excess power
(B) Transferring charge between cells
(C) Reducing voltage reference
(D) Disconnecting high-voltage cells

10. The BMS communicates with other vehicle systems through:
(A) CAN bus
(B) USB port
(C) Fiber optics
(D) HDMI

11. The BMS protects the battery from:
(A) Mechanical shocks
(B) Overvoltage, undervoltage, and overcurrent conditions
(C) Dust and water
(D) Temperature-independent reactions

12. A thermal runaway in batteries occurs when:
(A) Cooling system stops
(B) Battery temperature increases uncontrollably due to internal reactions
(C) Motor overheats
(D) Charger is disconnected

13. The BMS can disconnect the battery pack using:
(A) Thermal fuses
(B) Contactor or relay switches
(C) Diodes
(D) Capacitors

14. The primary goal of a BMS in EVs is to:
(A) Improve engine torque
(B) Extend battery life and ensure safety
(C) Increase charging voltage only
(D) Reduce air resistance

15. Coulomb counting is a method used to estimate:
(A) Battery temperature
(B) Battery voltage
(C) Battery SOC
(D) Battery resistance

16. The typical voltage range of a lithium-ion cell is:
(A) 0.5–1.5V
(B) 1.2–2.5V
(C) 2.5–4.2V
(D) 5–10V

17. The balancing circuit in BMS helps prevent:
(A) Uneven aging and capacity loss
(B) Voltage increase
(C) Power factor issues
(D) Speed reduction

18. Temperature sensors in BMS are usually:
(A) Thermistors or RTDs
(B) Potentiometers
(C) Resistors
(D) Inductors

19. The main cause of cell imbalance is:
(A) Equal self-discharge rates
(B) Unequal internal resistance and self-discharge
(C) Equal charging conditions
(D) Balanced temperature distribution

20. The BMS monitors the battery pack through:
(A) Sensors and communication circuits
(B) Only voltage probes
(C) Optical devices
(D) GPS modules

21. The current sensor in BMS is used for:
(A) Measuring current flow in or out of the battery
(B) Measuring air pressure
(C) Balancing cells
(D) Estimating cell temperature

22. An essential protection feature of BMS is:
(A) Isolation detection
(B) Noise amplification
(C) Magnetic coupling
(D) Data compression

23. The BMS estimates battery SOH based on:
(A) Capacity fade and internal resistance
(B) Temperature variation only
(C) Voltage difference only
(D) Power output

24. The thermal management system in BMS maintains:
(A) Cell temperature within a safe operating range
(B) Maximum voltage
(C) Constant SOC
(D) Motor efficiency

25. The key challenge in designing BMS for EVs is:
(A) Managing large numbers of cells safely
(B) Increasing charging time
(C) Reducing communication signals
(D) Limiting power output

26. The high-voltage isolation feature of BMS ensures:
(A) Protection from electric shock
(B) Faster charging
(C) Reduced motor losses
(D) Increased voltage output

27. The balancing current in passive BMS systems is typically:
(A) Very high (>10A)
(B) Moderate (1–2A)
(C) Low (10–200mA)
(D) Zero

28. The open-circuit voltage (OCV) method for SOC estimation is based on:
(A) Relationship between cell voltage and SOC when no load is applied
(B) Current flow direction
(C) Thermal balance
(D) Voltage ripple

29. A modular BMS architecture means:
(A) The system is divided into independent monitoring units
(B) All cells are connected to one sensor
(C) The system operates without communication
(D) BMS and charger are combined into one

30. The data collected by BMS is used for:
(A) Diagnostics, performance optimization, and safety monitoring
(B) Controlling motor speed directly
(C) Powering headlights
(D) Improving brake efficiency