Battery Management System Quiz Based on Chapter 1 • Point value: +1 for correct, -0.5 for incorrect. 1. What is the first and foremost purpose of a battery-management system (BMS)? To prolong the life of the battery To protect the safety of the operator To estimate state of charge To balance the cells 2. What is the rule of thumb regarding the cost of advanced BMS methods? A BMS should not exceed 10% of the pack cost. Your battery is ‘cheap enough’ if you can’t remember the last time you replaced it. Complex algorithms always justify their cost. BMS cost should be proportional to vehicle weight. 3. Which type of vehicle has essentially zero all-electric vehicle range and is never plugged in? PHEV E-REV EV HEV 4. What characterizes a Plug-in Hybrid-Electric Vehicle (PHEV)? No gasoline engine Zero all-electric range Can operate in electric-only mode for 10-20 miles and can be plugged in Never uses the gasoline engine 5. In battery pack topology, wiring cells in series increases: Pack current Pack voltage Cell resistance Cell capacity 6. Wiring cells in parallel increases: Pack current Pack voltage Pack temperature Individual cell voltage 7. What is the typical safety voltage limit for battery modules? Less than 12V Less than 50V Less than 100V Less than 600V 8. What is the Parallel-Cell-Module (PCM) approach? Wiring cells in series to make modules, then parallel Wiring cells in parallel to make modules, then modules in series Wiring all cells in parallel Alternating parallel and series at the cell level 9. What is the Series-Cell-Module (SCM) approach? Wiring cells in parallel, then series Wiring cells in series to make modules, then modules in parallel Wiring all cells in series only Using a single large cell 10. Why must all individual cell voltages be measured in a lithium-ion battery pack? Because cells automatically balance themselves To calculate the total energy used by the load Out-of-bounds cell voltage indicates serious lifetime and safety issues It is required for cooling system operation 11. How does a Negative-Temperature-Coefficient (NTC) thermistor behave? Resistance varies directly with temperature Resistance varies inversely with temperature Voltage is directly proportional to temperature Resistance remains constant 12. How is a thermistor typically measured in a BMS? Using a thermocouple Using a Hall-effect sensor Using a voltage-divider circuit Using a current shunt 13. What is a primary advantage of current shunts over Hall-effect sensors? They are automatically electrically isolated They introduce no energy losses They have no offset at zero current Their resistance does not change with temperature 14. What is a major disadvantage of Hall-effect current sensors? They introduce significant heat losses They lack electrical isolation They suffer from measurement offset at zero current that drifts They are too large for battery packs 15. Why is a precharge contactor used during the battery pack startup sequence? To test the electrical isolation of the pack To bypass a blown fuse To limit the huge spike of current into a discharged capacitive load To quickly charge the 12V auxiliary battery 16. What is the correct sequence for closing contactors during startup? Positive, Negative, Precharge Precharge, Negative, Positive Negative, Precharge, Positive All simultaneously 17. According to the safety metric, isolation is sufficient if the isolation resistance (Ri) is greater than: 100 * vb 200 * vb 500 * vb 1000 * vb 18. Which communication protocol is used almost exclusively for on-board vehicle messaging? I2C SPI CAN (Control-area network) UART 19. What is the purpose of the BMS log book function? To track vehicle speed To store a log of atypical and abuse events, and persistent diagnostics To record the driver’s routes To play media files 20. Why is the term ‘battery-pack SOC’ considered ill-defined? Because SOC cannot be measured Because defining it as 0% or 100% fails to accurately reflect if the pack can actually be safely charged or discharged due to imbalance Because it relies on current sensors Because it is not used in EVs 21. How is individual cell total energy calculated? By multiplying nominal voltage and present current By taking the integral of the cell’s OCV curve between the min SOC and present SOC, scaled by total capacity By integrating the current over time By measuring the temperature change 22. What does the Hybrid Pulse Power Characterization (HPPC) method compute? Estimates of available power by enforcing design limits on cell terminal voltage using a simplified equivalent-circuit model The internal electrochemical states of the cell The exact state of health Isolation resistance 23. Which two quantities are most commonly estimated to summarize battery pack State of Health (SOH)? SOC and temperature Total capacity and equivalent series resistance Voltage and current Isolation resistance and leakage current 24. What happens if a poor battery-controls algorithm incorrectly indicates ample power is available? The vehicle drives perfectly It will automatically balance the cells The battery pack may abruptly decrease allowed power, leading to poor drivability or hazards The battery pack cools down 25. Which estimate is most important for a pure Electric Vehicle (EV) to calculate remaining driving range? Instantaneous power Energy SOH Isolation resistance 26. How is battery-pack charge power computed in the simple HPPC method? By summing the minimum discharge powers of all cells By multiplying the minimum absolute cell power by the number of series-connected cells By multiplying the maximum absolute cell charge power by the number of series-connected cells By averaging the charge limits of all modules 27. What is the primary effect of overcharging a lithium-ion cell? It cleans the electrodes It initiates unwanted internal chemical side reactions that degrade the cell It decreases internal resistance It increases total capacity permanently 28. What is the primary effect of overdischarging a lithium-ion cell? It improves cell balancing It precipitates a sequence of events leading to a cell short-circuiting It increases the open-circuit voltage It decreases the leakage current 29. What happens during thermal runaway? The battery pack becomes extremely cold Heat generated by side reactions or short circuits accelerates failure mechanisms via positive feedback, resulting in fire or explosion The BMS shuts down the vehicle safely The cells balance themselves automatically 30. What is the purpose of the 16-bit CRC in a CAN message frame? To set the priority of the message For transmission error detection To address the recipient To indicate the end of the frame 31. What is the role of the BMS in thermal control? To heat the passenger cabin To control the thermal-management system to maintain battery-pack temperatures in a safe region To measure the outside air temperature To ignite the battery during an accident 32. What is the ideal temperature band for lithium-ion cells to last longest? -20°C to 0°C 0°C to 10°C 10°C to 40°C 40°C to 80°C 33. How is internal heat generation in a cell crudely approximated? Voltage divided by Resistance Current squared times Resistance (i^2R) Voltage squared times Current Capacity times Temperature 34. Which application typically requires liquid cooling due to high C-rates? EV HEV Consumer electronics Remote controls 35. What is the ‘safety margin’ in designing battery protection? The distance between the cells The buffer between the cell’s operating region and the manufacturer-specified failure zone The extra capacity added to the pack The physical casing of the battery 36. What is ‘random charging’ in the context of an xEV? Plugging the vehicle into any random wall outlet Charge delivered in unpredictable patterns, such as from regenerative braking Charging the 12V battery from the high-voltage pack Charging cells out of order 37. What limits the speed of plug-in charging for a modern EV? The size of the charging cable The vehicle’s weight The power available from the utility service feeding the charger The CAN bus speed 38. What is ‘coulomb counting’? Counting the number of cells in the pack Updating SOC by integrating measured current into and out of the battery pack Calculating the resistance of the cell Measuring the voltage of each cell 39. Why is the offset of a Hall-effect sensor at zero current problematic? It causes the battery to catch fire It plays havoc with coulomb counting SOC estimation over time It prevents voltage measurement It drains the battery completely 40. What happens if bus and battery-stack voltages don’t converge quickly during the precharge sequence? The BMS turns on the air conditioning The BMS assumes a short-circuit fault in the load and aborts startup The BMS closes the positive contactor anyway The BMS enters random charging mode 41. What is a thermal fuse? A device that measures temperature A device that opens the contactor when temperature is above some limiting temperature A device that heats the battery A cooling fan 42. Why are fallback protection paths implemented in BMS design? To increase the cost of the BMS To provide redundancy and ensure a robust protection scheme To improve the vehicle’s speed To make the software smaller 43. What is the unit of measure for Energy? Amperes (A) Volts (V) Watt-hours (Wh) or Kilowatt-hours (kWh) Watts (W) or Kilowatts (kW) 44. What is the unit of measure for Power? Amperes (A) Volts (V) Watt-hours (Wh) Watts (W) or Kilowatts (kW) 45. In the HPPC method, what values are used for discharge and charge resistance? The pure ohmic resistance R0 The effective resistance values calculated over a specific time horizon ΔT Zero The isolation resistance 46. What is power fade? The decrease of cell total capacity The increase of cell internal resistance over time The dimming of the dashboard lights The loss of CAN bus signal 47. What is capacity fade? The loss of cell internal resistance The decrease of cell total capacity over its service life The fading of the battery casing color The reduction of leakage current 48. What is the purpose of the 1-bit RTR flag in a CAN message? To detect transmission errors To indicate whether it is a data frame or a remote frame To signal the end of the frame To address the recipient 49. Why is a four-wire Kelvin connection used for current shunts? To provide backup power To measure temperature simultaneously To avoid voltage drop across the uncalibrated resistance of large screw terminals To double the current capacity 50. According to the book, what is the consequence of a ‘battery-pack SOC’ being ill-defined? We should rely on ‘battery-pack-average SOC’ instead, but truly need individual cell SOCs We must discard the BMS We only need to measure the total pack voltage We cannot use lithium-ion batteries Submit Quiz