1. What is a Battery Management System (BMS)?
It is the control system that monitors, protects, and manages rechargeable batteries, ensuring safe and efficient operation.
2. What are the main functions of a BMS?
- Measure voltage, current, and temperature
- Calculate SOC and SOH
- Control charging and discharging
- Balance cell voltages
- Protect against overcharge or over-discharge
3. What is SOC?
State of Charge, the remaining charge in the battery expressed as a percentage of total capacity.
4. What is SOH?
State of Health, the condition of a battery compared to its original performance.
5. What is cell balancing?
Equalizing the charge of all battery cells to maintain uniform performance and prevent damage.
6. What are the two types of cell balancing?
- Passive balancing
- Active balancing
7. What is passive balancing?
It dissipates excess energy from high cells as heat using resistors.
8. What is active balancing?
It transfers energy from higher cells to lower cells using converters, improving efficiency.
9. What sensors are used in a BMS?
Voltage sensors, current sensors, and temperature sensors (NTC/PTC).
10. What is a contactor?
An electrically controlled switch used to connect or disconnect high-voltage battery circuits.
11. What is precharge?
It limits inrush current when connecting the battery to the inverter using a resistor path before closing the main contactor.
12. What is isolation monitoring?
It checks that there is no leakage between high-voltage lines and vehicle chassis for safety.
13. What is thermal runaway?
A dangerous chain reaction where temperature increases rapidly, leading to battery fire or explosion.
14. What are the main protections in a BMS?
- Overvoltage
- Undervoltage
- Overcurrent
- Overtemperature
- Short circuit
15. What is a battery pack architecture?
It defines how cells, modules, and packs are arranged and connected electrically and mechanically.
16. What is a battery module?
A group of cells connected in series or parallel for higher voltage or capacity.
17. What is the main communication protocol used in BMS?
CAN is the most common protocol for communication between BMS and other ECUs.
18. What is a BMS master-slave architecture?
The Master BMS controls multiple Slave BMS boards that measure cell voltages and temperatures.
19. What is battery modeling?
Creating mathematical or Simulink models to predict battery behavior like voltage, SOC, and temperature.
20. What is an equivalent circuit model of a battery?
A simple electrical model using resistors and capacitors to simulate battery voltage and current response.
21. What is coulomb counting?
A method to calculate SOC by integrating current over time.
22. What is open-circuit voltage (OCV)?
The battery voltage measured when no load is connected.
23. What is SOC estimation error?
Difference between actual and estimated SOC caused by sensor noise, temperature, and modeling errors.
24. What is the Kalman Filter used for in BMS?
It estimates SOC more accurately using sensor data and model predictions.
25. What is BMS fault diagnosis?
Detection of faults like cell imbalance, open wire, or temperature sensor failure.
26. What is an EV control unit (VCU)?
It coordinates all powertrain systems like motor control, inverter, and BMS.
27. What is the role of a motor controller in EV?
It converts DC power from the battery into AC power for the electric motor and controls torque and speed.
28. What are the common types of motors used in EVs?
- Permanent Magnet Synchronous Motor (PMSM)
- Induction Motor (IM)
- Brushless DC Motor (BLDC)
29. What is regenerative braking?
It converts braking energy into electrical energy and stores it back in the battery.
30. What is torque control in EVs?
It regulates motor torque output based on accelerator pedal input and driving mode.
31. What is inverter efficiency?
The ratio of AC output power to DC input power of the inverter.
32. What is the DC-DC converter used for in EVs?
It converts high-voltage DC from the traction battery to low-voltage DC (12V) for auxiliary loads.
33. What is HVIL?
High Voltage Interlock Loop ensures the system shuts down safely if any high-voltage connector is opened.
34. What is the charging control unit?
It manages AC and DC charging, communicates with the charger, and ensures safe charging conditions.
35. What are charging standards used in EVs?
- CCS (Combined Charging System)
- CHAdeMO
- GB/T
- Type 2
36. What is V2G?
Vehicle-to-Grid allows energy flow from the vehicle battery back to the power grid.
37. What is Embedded C?
A version of the C language optimized for programming microcontrollers in embedded systems.
38. What are key features of Embedded C?
- Low-level hardware access
- Real-time performance
- Small memory use
- Portability
39. What is a microcontroller?
A small computer on a single chip with CPU, memory, and peripherals used in ECUs.
40. What is the difference between volatile and non-volatile memory?
Volatile memory loses data when power is off.
Non-volatile memory retains data, like Flash or EEPROM.
41. What is a pointer in C?
A variable that stores the address of another variable.
42. What is an interrupt service routine (ISR)?
A function that executes automatically when a specific interrupt occurs.
43. What is the use of the “volatile” keyword?
It tells the compiler not to optimize the variable because its value can change unexpectedly, such as by hardware.
44. What is a state machine in ECU software?
It defines different operating states (like idle, run, fault) and transitions between them.
45. What is PWM?
Pulse Width Modulation, a method to control power to actuators like motors or heaters.
46. What is ADC in microcontrollers?
Analog to Digital Converter converts analog signals (like temperature or voltage) into digital values for processing.
47. What is DAC?
Digital to Analog Converter converts digital signals back into analog form.
48. What is the purpose of a CAN driver in ECU software?
It sends and receives CAN messages through the microcontroller’s CAN controller.
49. What is debouncing in embedded systems?
It removes unwanted rapid signal changes from mechanical switches or buttons.
50. What are common debugging tools used in ECU software development?
- JTAG or Lauterbach debugger
- CANalyzer/CANoe
- Oscilloscope
- Serial monitor