Q.1 Which of the following is the primary chemical reaction that occurs in a lead‑acid battery during discharge?
Pb + H₂SO₄ → PbSO₄ + H₂
PbO₂ + Pb + 2H₂SO₄ → 2PbSO₄ + 2H₂O
PbO + H₂SO₄ → PbSO₄ + H₂O
PbSO₄ + H₂O → PbO₂ + H₂
Explanation - During discharge, lead dioxide (PbO₂) at the positive plate and metallic lead (Pb) at the negative plate react with sulfuric acid to form lead sulfate (PbSO₄) and water.
Correct answer is: PbO₂ + Pb + 2H₂SO₄ → 2PbSO₄ + 2H₂O
Q.2 What is the nominal voltage of a single lithium‑ion (Li‑ion) cell?
1.2 V
1.5 V
3.6 V
4.2 V
Explanation - A typical Li‑ion cell has a nominal voltage of about 3.6–3.7 V, derived from the Li⁺/Li redox couple.
Correct answer is: 3.6 V
Q.3 Which material is most commonly used as the cathode active material in modern Li‑ion batteries?
Lithium cobalt oxide (LiCoO₂)
Lithium iron phosphate (LiFePO₄)
Lithium manganese oxide (LiMn₂O₄)
All of the above
Explanation - Depending on the application, LiCoO₂, LiFePO₄, and LiMn₂O₄ are all widely used cathode chemistries.
Correct answer is: All of the above
Q.4 In a supercapacitor, energy is stored primarily by:
Chemical reactions
Electrostatic double‑layer formation
Phase change of the electrolyte
Magnetic fields
Explanation - Supercapacitors store energy via the formation of an electric double layer at the electrode–electrolyte interface, not by faradaic reactions.
Correct answer is: Electrostatic double‑layer formation
Q.5 Which of the following is a key advantage of solid‑state batteries over conventional liquid‑electrolyte Li‑ion batteries?
Higher energy density
Lower cost of production
Unlimited cycle life
No need for a separator
Explanation - Solid‑state electrolytes can enable higher voltage cathodes and lithium metal anodes, increasing the energy density. Cost and cycle life are still under development.
Correct answer is: Higher energy density
Q.6 The term "C‑rate" in battery specifications refers to:
Capacity measured in coulombs
Charging/discharging current relative to the battery's rated capacity
Temperature coefficient of the cell
Cut‑off voltage of the battery
Explanation - A 1C rate means the battery is charged or discharged in one hour; 2C would be in half an hour, etc.
Correct answer is: Charging/discharging current relative to the battery's rated capacity
Q.7 Which electrolyte is most commonly used in nickel‑metal hydride (Ni‑MH) batteries?
Sulfuric acid
Potassium hydroxide (KOH)
Lithium hexafluorophosphate (LiPF₆)
Sodium chloride solution
Explanation - Ni‑MH batteries use an alkaline KOH electrolyte, similar to nickel‑cadmium cells.
Correct answer is: Potassium hydroxide (KOH)
Q.8 What is the main cause of capacity fade in lithium‑ion batteries over many charge‑discharge cycles?
Loss of electrolyte due to evaporation
Growth of the solid electrolyte interphase (SEI) layer on the anode
Corrosion of the metal casing
Decrease in separator thickness
Explanation - Repeated cycling thickens the SEI, consuming active lithium and increasing internal resistance, leading to capacity loss.
Correct answer is: Growth of the solid electrolyte interphase (SEI) layer on the anode
Q.9 Which of the following is NOT a typical characteristic of a flow battery?
Energy storage in liquid electrolytes
Separate tanks for active materials
High power density comparable to Li‑ion cells
Scalable energy capacity by increasing tank size
Explanation - Flow batteries usually have lower power density; they excel in scalability and long cycle life.
Correct answer is: High power density comparable to Li‑ion cells
Q.10 The theoretical specific energy of a lithium‑sulfur (Li‑S) battery is about:
100 Wh/kg
250 Wh/kg
500 Wh/kg
800 Wh/kg
Explanation - Li‑S chemistry offers a theoretical specific energy of around 500 Wh kg⁻¹, far higher than conventional Li‑ion batteries.
Correct answer is: 500 Wh/kg
Q.11 In the context of battery safety, "thermal runaway" is primarily triggered by:
Excessive mechanical vibration
Over‑charging leading to internal heat generation
Low ambient temperature
High internal resistance due to aging
Explanation - Over‑charging can cause exothermic side reactions, generating heat that may accelerate further reactions, leading to thermal runaway.
Correct answer is: Over‑charging leading to internal heat generation
Q.12 Which of the following is a common method to improve the cycle life of a Li‑ion battery?
Using a thicker separator
Adding lithium‑metal anode
Incorporating electrolyte additives that stabilize the SEI
Operating at higher temperatures
Explanation - Additives such as vinylene carbonate help form a more stable SEI, reducing degradation and extending cycle life.
Correct answer is: Incorporating electrolyte additives that stabilize the SEI
Q.13 Which of the following battery chemistries is considered the most environmentally friendly due to its lack of toxic heavy metals?
Lead‑acid
Nickel‑cadmium (Ni‑Cd)
Lithium‑ion (Li‑ion)
Sodium‑ion (Na‑ion)
Explanation - Na‑ion batteries avoid heavy metals like cobalt and lead, using abundant sodium and relatively benign electrode materials.
Correct answer is: Sodium‑ion (Na‑ion)
Q.14 A battery's "state of charge" (SOC) can be estimated by measuring:
Open‑circuit voltage (OCV)
Internal resistance only
Temperature rise during discharge
Physical size of the battery
Explanation - The OCV of many chemistries correlates with SOC; other methods (Coulomb counting) are also used, but OCV is a direct indicator.
Correct answer is: Open‑circuit voltage (OCV)
Q.15 Which material is commonly used as the anode in a lithium‑ion battery?
Graphite
Lithium cobalt oxide
Nickel hydroxide
Lead dioxide
Explanation - Graphite provides a stable host for lithium intercalation/de‑intercalation, making it the standard anode material.
Correct answer is: Graphite
Q.16 The energy density of a battery is expressed in:
W (watts)
Wh (watt‑hours)
Wh/kg (watt‑hours per kilogram)
V (volts)
Explanation - Energy density is the amount of energy stored per unit mass, measured in Wh/kg.
Correct answer is: Wh/kg (watt‑hours per kilogram)
Q.17 Which of the following factors has the greatest impact on the internal resistance of a battery?
Electrode surface area
Separator thickness
Electrolyte conductivity
Cell voltage
Explanation - Higher electrolyte conductivity lowers the ionic resistance, which is a major component of the total internal resistance.
Correct answer is: Electrolyte conductivity
Q.18 What does the term "depth of discharge" (DoD) refer to in battery usage?
Maximum voltage the battery can reach
Percentage of the battery capacity that has been used
Temperature drop during discharge
Number of cycles the battery has completed
Explanation - DoD = (capacity used / total capacity) × 100%; a lower DoD generally leads to longer cycle life.
Correct answer is: Percentage of the battery capacity that has been used
Q.19 Which of the following statements about a battery management system (BMS) is FALSE?
It balances cell voltages during charging.
It monitors temperature and prevents overheating.
It directly increases the cell's nominal voltage.
It provides over‑current protection.
Explanation - A BMS manages and protects cells but cannot change their inherent voltage; it only ensures safe operation.
Correct answer is: It directly increases the cell's nominal voltage.
Q.20 In a Nickel‑Metal Hydride (Ni‑MH) cell, the overall discharge reaction can be written as:
NiOOH + MH → Ni(OH)₂ + M + H₂O
Ni(OH)₂ + MH + H₂O → NiOOH + M + 2H₂O
2NiOOH + H₂ → 2Ni(OH)₂ + H₂
NiOOH + H₂ → Ni + H₂O
Explanation - During discharge, nickel oxyhydroxide (NiOOH) is reduced to nickel hydroxide (Ni(OH)₂) while the metal hydride (MH) is oxidized to metal (M) and releases water.
Correct answer is: NiOOH + MH → Ni(OH)₂ + M + H₂O
Q.21 Which of these is a common cause of self‑discharge in batteries?
Leakage of electrolyte
Diffusion of active species across the separator
External short‑circuit
All of the above
Explanation - Self‑discharge can be due to internal leakage, diffusion of species, or inadvertent short circuits within the cell.
Correct answer is: All of the above
Q.22 A battery rated at 2000 mAh and 3.7 V stores how much energy?
7.4 Wh
3.7 Wh
2.0 Wh
5.6 Wh
Explanation - Energy (Wh) = Capacity (Ah) × Voltage (V) = 2 Ah × 3.7 V = 7.4 Wh.
Correct answer is: 7.4 Wh
Q.23 Which of the following is the main reason why lithium‑metal anodes are challenging to use in commercial batteries?
Low theoretical capacity
Formation of dendrites leading to short circuits
High cost of lithium metal
Incompatibility with organic electrolytes
Explanation - Lithium dendrite growth can pierce the separator and cause internal shorts, posing safety risks.
Correct answer is: Formation of dendrites leading to short circuits
Q.24 In a rechargeable battery, what does the term "coulombic efficiency" describe?
Ratio of energy out to energy in during a cycle
Ratio of charge extracted to charge put in during a cycle
Amount of heat generated per cycle
Voltage drop across the internal resistance
Explanation - Coulombic efficiency = (discharge capacity ÷ charge capacity) × 100%; high values (>99 %) indicate low loss of charge carriers.
Correct answer is: Ratio of charge extracted to charge put in during a cycle
Q.25 Which of the following battery technologies typically offers the highest power density?
Lead‑acid
Lithium‑ion
Supercapacitor
Sodium‑sulfur (Na‑S)
Explanation - Supercapacitors can deliver very high power quickly due to their electrostatic charge storage mechanism.
Correct answer is: Supercapacitor
Q.26 What is the primary function of a separator in a battery cell?
Conduct electrons between electrodes
Prevent physical contact between anode and cathode while allowing ion flow
Store electrolyte
Act as a mechanical support for the case
Explanation - The separator is a porous, electrically insulating membrane that permits ion migration but blocks electron flow.
Correct answer is: Prevent physical contact between anode and cathode while allowing ion flow
Q.27 Which electrolyte type is used in most commercial lithium‑ion batteries?
Aqueous KOH solution
Organic carbonate solvents with LiPF₆ salt
Molten salt
Solid polymer electrolyte
Explanation - A mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) with LiPF₆ is the standard electrolyte for Li‑ion cells.
Correct answer is: Organic carbonate solvents with LiPF₆ salt
Q.28 The term "energy storage material" in the context of batteries most often refers to:
The metal casing
Electrode active material
The separator
The external wiring
Explanation - Energy is stored in the reversible chemical reactions occurring in the electrode active materials.
Correct answer is: Electrode active material
Q.29 Which of the following statements about the Peukert effect is correct?
Battery capacity increases with higher discharge rates.
Battery capacity decreases with higher discharge rates.
Battery voltage remains constant regardless of discharge current.
Peukert effect only applies to rechargeable batteries.
Explanation - Peukert's law quantifies how the usable capacity of a lead‑acid battery drops as the discharge current increases.
Correct answer is: Battery capacity decreases with higher discharge rates.
Q.30 Which battery technology is currently being explored for grid‑scale storage due to its long cycle life and low cost?
Lithium‑ion
Lead‑acid
Flow batteries (e.g., vanadium redox)
Alkaline primary cells
Explanation - Vanadium redox flow batteries can be scaled easily, have long lifetimes, and are suitable for large stationary storage.
Correct answer is: Flow batteries (e.g., vanadium redox)
Q.31 In a lithium‑ion cell, what role does the "solid electrolyte interphase" (SEI) play?
It conducts electrons between electrodes.
It acts as a protective layer that allows Li⁺ transport while preventing electrolyte decomposition.
It stores the majority of the cell's energy.
It provides mechanical strength to the electrode.
Explanation - The SEI forms on the anode during initial cycles, stabilizing the interface and allowing only Li⁺ to pass.
Correct answer is: It acts as a protective layer that allows Li⁺ transport while preventing electrolyte decomposition.
Q.32 Which of these is a disadvantage of lead‑acid batteries compared to Li‑ion batteries?
High energy density
Low self‑discharge rate
Heavy weight and low specific energy
No need for a BMS
Explanation - Lead‑acid batteries have relatively low specific energy (~30‑40 Wh/kg) and are heavy, making them less suitable for portable applications.
Correct answer is: Heavy weight and low specific energy
Q.33 The open‑circuit voltage (OCV) of a fully charged Li‑ion cell is typically around:
2.0 V
3.0 V
3.7 V
4.2 V
Explanation - A fully charged Li‑ion cell reaches about 4.2 V (nominal 3.7 V). The 3.7 V figure is the average voltage during discharge.
Correct answer is: 4.2 V
Q.34 Which material is commonly used as a cathode current collector in Li‑ion batteries?
Copper foil
Aluminium foil
Stainless steel
Nickel mesh
Explanation - Aluminium is chemically stable at the high potentials of Li‑ion cathodes, whereas copper would oxidize.
Correct answer is: Aluminium foil
Q.35 What does the term "specific power" of a battery denote?
Energy per unit mass
Power per unit mass
Voltage per unit volume
Charge per unit time
Explanation - Specific power (W/kg) indicates how quickly a battery can deliver its stored energy relative to its weight.
Correct answer is: Power per unit mass
Q.36 Which of the following is a major safety concern for lithium‑ion batteries when they are physically damaged?
Electrolyte leakage leading to corrosion
Internal short circuit causing thermal runaway
Rapid self‑discharge without heat
Loss of magnetic properties
Explanation - Mechanical damage can breach the separator, allowing the anode and cathode to touch and generate heat quickly.
Correct answer is: Internal short circuit causing thermal runaway
Q.37 Which of the following battery chemistries uses a molten salt electrolyte that operates at temperatures above 300 °C?
Lead‑acid
Sodium‑sulfur (Na‑S)
Lithium‑ion
Nickel‑metal hydride
Explanation - Na‑S batteries employ molten sodium and sulfur as electrodes with a molten salt electrolyte, requiring high operating temperatures.
Correct answer is: Sodium‑sulfur (Na‑S)
Q.38 What is the main advantage of using a lithium‑ion polymer (Li‑poly) battery over a conventional Li‑ion cylindrical cell?
Higher voltage per cell
Flexible form factor and thinner packaging
Cheaper raw materials
Longer cycle life
Explanation - Li‑poly cells use a solid or gel polymer electrolyte, allowing them to be shaped to fit space‑constrained designs.
Correct answer is: Flexible form factor and thinner packaging
Q.39 Which of the following degradation mechanisms is most prominent in nickel‑based batteries during high‑temperature operation?
Lithium plating
Positive electrode corrosion
SEI growth
Electrolyte evaporation
Explanation - High temperatures accelerate the corrosion of nickel‑based cathodes, leading to capacity loss.
Correct answer is: Positive electrode corrosion
Q.40 In a battery pack, why are cells often connected in series?
To increase the total voltage
To increase the total capacity
To reduce internal resistance
To balance temperature
Explanation - Series connection adds the voltages of individual cells while the capacity (Ah) remains the same.
Correct answer is: To increase the total voltage
Q.41 What is the typical nominal voltage of a nickel‑metal hydride (Ni‑MH) cell?
0.9 V
1.2 V
1.5 V
2.0 V
Explanation - Ni‑MH cells have a nominal voltage of about 1.2 V, similar to Ni‑Cd cells.
Correct answer is: 1.2 V
Q.42 Which of the following is a primary cause of voltage sag in a battery under high current demand?
Increase in electrolyte conductivity
Decrease in internal resistance
IR drop due to internal resistance
Growth of the SEI layer
Explanation - When high current flows, the product of current (I) and internal resistance (R) causes a voltage drop (IR), reducing the terminal voltage.
Correct answer is: IR drop due to internal resistance
Q.43 Which of the following is NOT a typical component of a battery management system (BMS)?
Voltage sensors
Temperature sensors
Fuel gauge
Current shunt
Explanation - Fuel gauge terminology is used in automotive fuel systems, not in BMS hardware.
Correct answer is: Fuel gauge
Q.44 What is the main difference between a primary (non‑rechargeable) battery and a secondary (rechargeable) battery?
Primary batteries have higher voltage.
Secondary batteries can undergo reversible electrochemical reactions.
Primary batteries are always larger in size.
Secondary batteries use liquid electrolytes only.
Explanation - Rechargeable batteries allow the electrochemical reactions to be reversed during charging, unlike primary cells.
Correct answer is: Secondary batteries can undergo reversible electrochemical reactions.
Q.45 A battery pack rated at 48 V and 10 Ah stores how many watt‑hours of energy?
480 Wh
240 Wh
96 Wh
120 Wh
Explanation - Energy = Voltage × Capacity = 48 V × 10 Ah = 480 Wh.
Correct answer is: 480 Wh
Q.46 Which of the following is a typical characteristic of a lithium‑iron phosphate (LiFePO₄) cathode?
High voltage (~4.2 V) and high energy density
Excellent thermal stability and long cycle life
Low conductivity requiring carbon coating
Both B and C
Explanation - LiFePO₄ offers great thermal stability and long cycle life, but its electronic conductivity is low, so carbon coating is often added.
Correct answer is: Both B and C
Q.47 What does the term "energy density" specifically refer to in the context of batteries?
Energy per unit volume (Wh/L)
Power per unit mass (W/kg)
Voltage per unit area (V/cm²)
Current per unit temperature (A/°C)
Explanation - Energy density can be expressed as Wh/L (volumetric) or Wh/kg (gravimetric). It indicates how much energy a battery holds relative to its size or weight.
Correct answer is: Energy per unit volume (Wh/L)
Q.48 Which battery technology is most suitable for high‑temperature environments such as oil‑field applications?
Lithium‑ion
Lead‑acid
Sodium‑sulfur
Nickel‑cadmium
Explanation - Na‑S batteries operate at temperatures around 300 °C, making them ideal for high‑temperature settings.
Correct answer is: Sodium‑sulfur
Q.49 In the context of battery materials, what does the term "intercalation" mean?
Chemical reaction that permanently changes the electrode structure
Insertion of ions into the host material’s lattice without major structural changes
Formation of a solid electrolyte interphase
Evaporation of the electrolyte
Explanation - Intercalation involves reversible insertion/removal of ions (e.g., Li⁺) into layered structures like graphite.
Correct answer is: Insertion of ions into the host material’s lattice without major structural changes
Q.50 Which of the following phenomena can cause a sudden voltage drop at the end of a battery's discharge curve?
Electrolyte boiling
Polarization of the electrodes
SEI layer formation
Self‑discharge
Explanation - As the battery depletes, increased polarization leads to higher overpotentials and a rapid voltage decline.
Correct answer is: Polarization of the electrodes
Q.51 A battery pack uses 8 cells in series, each with a nominal voltage of 3.7 V. What is the pack's nominal voltage?
29.6 V
14.8 V
7.4 V
3.7 V
Explanation - Nominal pack voltage = number of cells × nominal cell voltage = 8 × 3.7 V = 29.6 V.
Correct answer is: 29.6 V
Q.52 Which of the following is a common method for measuring the state of health (SOH) of a battery?
Measuring the battery's weight
Monitoring the open‑circuit voltage over time
Performing impedance spectroscopy
Counting the number of times the battery is moved
Explanation - Impedance spectroscopy reveals changes in internal resistance and other parameters related to aging, helping estimate SOH.
Correct answer is: Performing impedance spectroscopy
Q.53 Which of the following is a key limitation of sodium‑ion batteries compared with lithium‑ion batteries?
Lower abundance of sodium
Higher operating voltage
Larger ionic radius leading to slower diffusion
Requirement of a solid‑state electrolyte
Explanation - Sodium ions (Na⁺) are larger than Li⁺, which can result in slower diffusion kinetics and lower power performance.
Correct answer is: Larger ionic radius leading to slower diffusion
Q.54 Which of the following statements about the 'cut‑off voltage' of a battery is true?
It is the voltage at which the battery must be disconnected to prevent over‑charging.
It is the voltage at which the battery must be disconnected to prevent deep discharge.
It is the voltage at which the battery reaches maximum power output.
Both A and B.
Explanation - Cut‑off voltages define safe limits for both over‑charging (upper limit) and deep discharge (lower limit).
Correct answer is: Both A and B.
Q.55 In a zinc‑air battery, the primary electrochemical reaction involves:
Zinc oxidation and oxygen reduction
Zinc reduction and oxygen oxidation
Zinc and hydrogen gas reaction
Zinc and chlorine reaction
Explanation - Zinc is oxidized at the anode while oxygen from the air is reduced at the cathode, delivering high energy density.
Correct answer is: Zinc oxidation and oxygen reduction
Q.56 Which battery technology is known for having a very low self‑discharge rate (less than 2 % per month)?
Lithium‑ion
Nickel‑cadmium
Lead‑acid
Alkaline primary
Explanation - Alkaline primary cells exhibit extremely low self‑discharge, making them suitable for long‑term storage.
Correct answer is: Alkaline primary
Q.57 The term "grid‑scale energy storage" most commonly refers to:
Small batteries used in smartphones
Large battery or storage systems that provide power to the electric grid
Portable power banks for laptops
Vehicle‑to‑grid (V2G) systems only
Explanation - Grid‑scale storage includes large installations (e.g., flow batteries, Li‑ion farms) that help balance supply and demand.
Correct answer is: Large battery or storage systems that provide power to the electric grid
Q.58 Which of the following is an example of a non‑electrochemical energy storage device?
Supercapacitor
Lithium‑ion battery
Lead‑acid battery
Ni‑MH battery
Explanation - Supercapacitors store energy electrostatically rather than through chemical reactions.
Correct answer is: Supercapacitor
Q.59 What is the typical voltage of a single alkaline primary cell (e.g., AA)?
1.2 V
1.5 V
3.0 V
3.7 V
Explanation - Alkaline cells have an open‑circuit voltage of about 1.5 V when new.
Correct answer is: 1.5 V
Q.60 Which of the following methods can be used to balance the state of charge among cells in a series‑connected battery pack?
Passive resistor shunting
Active DC‑DC converters
Both A and B
Neither A nor B
Explanation - Passive shunting dissipates excess energy as heat, while active converters move charge between cells more efficiently.
Correct answer is: Both A and B
Q.61 In a typical Li‑ion battery, which ion moves through the electrolyte during discharge?
Li⁺
Na⁺
K⁺
Mg²⁺
Explanation - Lithium ions migrate from the anode to the cathode through the electrolyte during discharge.
Correct answer is: Li⁺
Q.62 Which property of a battery electrolyte most directly affects the internal resistance of the cell?
Viscosity
Electrical conductivity
Color
Boiling point
Explanation - Higher ionic conductivity reduces the internal resistance, improving power performance.
Correct answer is: Electrical conductivity
Q.63 What is the primary advantage of a 'dual‑temperature' battery management system?
It can charge the battery faster.
It monitors both the cell temperature and ambient temperature for optimized safety.
It doubles the battery capacity.
It eliminates the need for voltage monitoring.
Explanation - Dual‑temperature BMS tracks internal and external temperatures to prevent overheating and improve longevity.
Correct answer is: It monitors both the cell temperature and ambient temperature for optimized safety.
Q.64 Which of the following is a characteristic advantage of using a gel‑polymer electrolyte in a Li‑ion battery?
Higher energy density than liquid electrolytes
Improved safety due to reduced leakage
Ability to operate at temperatures above 200 °C
Increased self‑discharge rate
Explanation - Gel‑polymer electrolytes are less likely to leak or ignite, enhancing safety, though they may have lower conductivity.
Correct answer is: Improved safety due to reduced leakage
Q.65 Which of the following statements about the 'Coulombic efficiency' of a battery is correct?
It is always exactly 100 % for rechargeable batteries.
It is typically slightly less than 100 % due to side reactions.
It is unrelated to the charge‑discharge cycles.
It measures the battery's voltage stability.
Explanation - Inefficiencies such as SEI growth and parasitic reactions cause coulombic efficiency to be <100 %.
Correct answer is: It is typically slightly less than 100 % due to side reactions.
Q.66 Which of the following is a typical voltage range for a fully discharged lead‑acid cell?
12.0 V
2.0 V
1.75 V
3.7 V
Explanation - A lead‑acid cell is considered fully discharged around 1.75 V per cell (12 V battery = 6 cells).
Correct answer is: 1.75 V
Q.67 Which battery technology is most often used in electric aircraft concepts due to its high specific energy?
Lead‑acid
Lithium‑sulfur
Nickel‑metal hydride
Zinc‑air
Explanation - Li‑S offers very high specific energy (~500 Wh/kg), making it attractive for weight‑critical applications like aircraft.
Correct answer is: Lithium‑sulfur
Q.68 What is the main purpose of adding a 'current interrupt device' (CID) in a battery pack?
To increase the charge capacity
To disconnect the pack in case of excessive current
To balance the cell voltages
To improve thermal conductivity
Explanation - A CID acts as a protective fuse, opening the circuit when current exceeds a safe threshold.
Correct answer is: To disconnect the pack in case of excessive current
Q.69 Which of the following is a typical failure mode of a lithium‑ion battery when stored at high state of charge for an extended period?
Lithium plating on the anode
Rapid self‑discharge
Increase in internal pressure due to gas generation
Both A and C
Explanation - High SOC storage can cause lithium plating and electrolyte decomposition, producing gas and increasing pressure.
Correct answer is: Both A and C
Q.70 The term "electrochemical window" of an electrolyte refers to:
The temperature range over which the electrolyte remains liquid
The voltage range within which the electrolyte is stable and does not decompose
The physical thickness of the electrolyte layer
The pH range of the electrolyte
Explanation - An electrolyte’s electrochemical window defines the safe operating voltage limits before oxidative or reductive breakdown.
Correct answer is: The voltage range within which the electrolyte is stable and does not decompose
Q.71 Which of the following battery chemistries is most commonly used in hybrid electric vehicles (HEVs) for its high power capability and durability?
Lithium‑ion
Nickel‑metal hydride
Lead‑acid
Zinc‑carbon
Explanation - Ni‑MH batteries have high power density and robust cycle life, making them suitable for HEVs like the Toyota Prius.
Correct answer is: Nickel‑metal hydride
Q.72 Which parameter is most directly related to the "fast‑charging" capability of a battery?
High internal resistance
Low diffusion coefficient of lithium ions in the electrode
High electronic conductivity of electrode materials
Low nominal voltage
Explanation - High electronic conductivity reduces voltage drop under high current, enabling faster charge acceptance.
Correct answer is: High electronic conductivity of electrode materials
Q.73 What is the primary advantage of using a 'prismatic' cell format over a cylindrical format?
Higher energy density per volume
Easier to cool
Lower manufacturing cost
Higher voltage
Explanation - Prismatic cells can be packed more efficiently, giving higher volumetric energy density in many applications.
Correct answer is: Higher energy density per volume
Q.74 In a battery pack, why is it important to monitor cell temperature individually rather than just pack temperature?
Because each cell may have different resistance and generate different heat
Because temperature does not affect battery performance
Because the pack temperature is always constant
Because monitoring only pack temperature reduces cost
Explanation - Cell‑to‑cell variations can cause localized heating; individual monitoring helps prevent thermal runaway.
Correct answer is: Because each cell may have different resistance and generate different heat
Q.75 Which of the following is a typical characteristic of a solid‑state battery compared with a conventional Li‑ion battery?
Higher flammability
Use of liquid electrolyte
Potential for higher energy density and improved safety
Lower operating voltage
Explanation - Solid electrolytes are non‑flammable and enable lithium metal anodes, raising energy density while enhancing safety.
Correct answer is: Potential for higher energy density and improved safety
Q.76 Which of the following degradation mechanisms is most closely associated with high charge rates in lithium‑ion batteries?
Lithium plating on the anode surface
Growth of the SEI layer
Separator shrinkage
Cathode delithiation
Explanation - Fast charging can cause Li⁺ to deposit as metallic lithium on the anode, leading to dendrite formation.
Correct answer is: Lithium plating on the anode surface
Q.77 Which of the following is NOT a typical advantage of using a battery management system (BMS) in electric vehicle applications?
Balancing cell voltages
Extending battery life
Increasing the vehicle's top speed directly
Providing safety cut‑offs
Explanation - A BMS manages battery health and safety but does not directly affect the vehicle's mechanical performance.
Correct answer is: Increasing the vehicle's top speed directly
Q.78 The term "redox flow battery" refers to a system where:
Energy is stored in solid electrodes only
Electrolyte solutions containing redox couples are stored in external tanks and pumped through a reactor
The battery uses solid polymer electrolytes
The battery can only be discharged, not charged
Explanation - In redox flow batteries, the active materials are dissolved in liquids that are stored separately, allowing easy scaling.
Correct answer is: Electrolyte solutions containing redox couples are stored in external tanks and pumped through a reactor
Q.79 Which of the following is a primary environmental concern associated with the disposal of lead‑acid batteries?
Release of toxic lead into soil and water
Emission of greenhouse gases
Generation of radioactive waste
Production of ozone‑depleting substances
Explanation - Improper disposal can leach lead, posing serious health and environmental risks.
Correct answer is: Release of toxic lead into soil and water
Q.80 In a lithium‑ion cell, which of the following is the typical anode material for high‑energy applications?
Graphite
Silicon‑based composite
Lithium metal
Tin oxide
Explanation - Silicon offers ~10× higher capacity than graphite, though it requires engineering to handle volume changes.
Correct answer is: Silicon‑based composite
Q.81 Which of the following battery chemistries is most resistant to memory effect?
Nickel‑cadmium (Ni‑Cd)
Nickel‑metal hydride (Ni‑MH)
Lithium‑ion (Li‑ion)
Lead‑acid
Explanation - Li‑ion batteries do not exhibit the memory effect seen in Ni‑Cd cells.
Correct answer is: Lithium‑ion (Li‑ion)
Q.82 What does the term "over‑potential" refer to in battery operation?
The extra voltage required to drive a non‑spontaneous electrochemical reaction at a given current
The voltage drop caused by a short circuit
The voltage difference between two cells in series
The maximum voltage a battery can reach during charging
Explanation - Over‑potential is the additional voltage beyond the thermodynamic equilibrium needed to overcome kinetic barriers.
Correct answer is: The extra voltage required to drive a non‑spontaneous electrochemical reaction at a given current
Q.83 Which of the following battery types typically uses a 'gel' electrolyte to improve safety?
Lead‑acid (gel type)
Lithium‑ion (liquid electrolyte)
Nickel‑cadmium
Alkaline primary
Explanation - Gel‑lead‑acid batteries immobilize the electrolyte, reducing the risk of spillage and enhancing vibration resistance.
Correct answer is: Lead‑acid (gel type)
Q.84 The main advantage of using a 'bipolar' design in a battery stack is:
Simplified wiring and reduced weight
Higher voltage per cell
Improved thermal management
All of the above
Explanation - Bipolar stacks share current collectors between cells, reducing interconnects, weight, and often improving heat dissipation.
Correct answer is: All of the above
Q.85 Which of the following is the most common cause of rapid capacity loss in a battery that is repeatedly deep‑discharged?
Increase in electrolyte viscosity
Mechanical deformation of electrodes
Accelerated side reactions and active material loss
Reduction of separator thickness
Explanation - Deep discharge stresses the electrodes, leading to increased side reactions, loss of active material, and thus faster capacity fade.
Correct answer is: Accelerated side reactions and active material loss
Q.86 Which of the following is NOT a typical parameter monitored by a battery management system (BMS)?
Cell voltage
Cell temperature
Cell mass
State of charge (SOC)
Explanation - BMS monitors electrical and thermal parameters; mass is not measured in real‑time.
Correct answer is: Cell mass
Q.87 Which of the following battery chemistries is most widely used in smartphones due to its high energy density and relatively low self‑discharge?
Lead‑acid
Lithium‑ion
Nickel‑cadmium
Alkaline
Explanation - Li‑ion cells offer high energy density (~150‑250 Wh/kg) and low self‑discharge (~1‑2 %/month), ideal for portable devices.
Correct answer is: Lithium‑ion
Q.88 What is the primary purpose of a 'separator' in a lithium‑ion cell?
To conduct electrons between the electrodes
To prevent direct electrical contact between anode and cathode while allowing ion flow
To store lithium ions
To act as a structural support for the cell case
Explanation - The separator is an electrically insulating but ion‑permeable membrane that keeps the electrodes apart.
Correct answer is: To prevent direct electrical contact between anode and cathode while allowing ion flow
Q.89 Which of the following factors most directly influences the 'cycle life' of a rechargeable battery?
Operating temperature
Physical size of the battery
Color of the battery case
Manufacturer's logo
Explanation - Higher temperatures accelerate degradation mechanisms, reducing the number of viable charge‑discharge cycles.
Correct answer is: Operating temperature
Q.90 In a battery, the term 'self‑discharge' refers to:
The loss of stored energy while the battery is not connected to a load
The intentional discharge of the battery for safety
The process of charging the battery
The increase of voltage when the battery is idle
Explanation - Self‑discharge occurs due to internal parasitic reactions, causing the battery voltage to drop over time even when unused.
Correct answer is: The loss of stored energy while the battery is not connected to a load
Q.91 Which of the following is a key characteristic of a 'high‑power' battery compared to a 'high‑energy' battery?
Higher specific energy (Wh/kg)
Lower internal resistance allowing rapid charge/discharge
Higher voltage per cell
Longer shelf life
Explanation - High‑power batteries prioritize low internal resistance for fast energy delivery, while high‑energy batteries focus on storing more energy per weight.
Correct answer is: Lower internal resistance allowing rapid charge/discharge
Q.92 Which battery type is commonly used in emergency lighting due to its long shelf life and reliability?
Lithium‑ion
Nickel‑cadmium
Lead‑acid (VRLA)
Alkaline primary
Explanation - Valve‑regulated lead‑acid (VRLA) batteries have low self‑discharge and can hold a charge for several years, suitable for standby power.
Correct answer is: Lead‑acid (VRLA)
Q.93 Which of the following is NOT a typical cause of thermal runaway in lithium‑ion batteries?
Over‑charging
Mechanical puncture
External cooling
High ambient temperature
Explanation - External cooling helps prevent thermal runaway; the other options can trigger it.
Correct answer is: External cooling
Q.94 What is the main role of the 'cathode' in a rechargeable battery?
To provide electrons to the external circuit during discharge
To store and release ions during charge and discharge
To act as a mechanical support
To regulate temperature
Explanation - During discharge, the cathode undergoes reduction, accepting electrons while releasing its stored ions into the electrolyte.
Correct answer is: To store and release ions during charge and discharge
Q.95 Which of the following battery chemistries typically exhibits the highest volumetric energy density?
Lithium‑ion
Nickel‑metal hydride
Lead‑acid
Alkaline primary
Explanation - Li‑ion cells have volumetric energy densities of 250‑700 Wh/L, surpassing most other chemistries.
Correct answer is: Lithium‑ion
Q.96 In a battery pack, what is the purpose of a 'balancing circuit'?
To equalize the state of charge among cells
To increase the total voltage of the pack
To reduce the overall weight of the pack
To change the chemistry of the cells
Explanation - Balancing circuits ensure that all cells reach similar SOC, preventing over‑charge or over‑discharge of individual cells.
Correct answer is: To equalize the state of charge among cells
Q.97 Which of the following is an advantage of using a 'gel' electrolyte in a lead‑acid battery?
Higher energy density than liquid electrolyte
Reduced risk of electrolyte spillage
Ability to operate at temperatures above 200 °C
Elimination of the need for a separator
Explanation - Gel electrolyte is immobilized, making the battery leak‑proof and better suited for mobile or vibration‑prone applications.
Correct answer is: Reduced risk of electrolyte spillage
Q.98 What does the term 'specific capacity' of a battery electrode refer to?
Charge stored per unit mass of the electrode (mAh/g)
Voltage per unit mass
Energy per unit volume
Current per unit temperature
Explanation - Specific capacity (mAh g⁻¹) measures how much charge can be stored per gram of active material.
Correct answer is: Charge stored per unit mass of the electrode (mAh/g)
Q.99 Which of the following is a key challenge for commercializing sodium‑ion batteries?
Scarcity of sodium resources
Low ionic conductivity of sodium ions in solid electrolytes
Excessive self‑discharge rates
Inability to operate at low temperatures
Explanation - Sodium's larger ionic radius makes fast transport in many solid electrolytes difficult, limiting rate performance.
Correct answer is: Low ionic conductivity of sodium ions in solid electrolytes
Q.100 Which of the following battery technologies is most suitable for high‑energy‑density applications such as drones?
Lead‑acid
Lithium‑polymer
Nickel‑cadmium
Zinc‑air
Explanation - Li‑poly cells offer high energy density and lightweight, flexible form factors ideal for UAVs.
Correct answer is: Lithium‑polymer
Q.101 What is the main reason that lithium‑sulfur batteries suffer from rapid capacity fade?
Lithium dendrite formation
Polysulfide shuttle effect causing active material loss
High self‑discharge
Low operating voltage
Explanation - Dissolved polysulfides migrate between electrodes, leading to loss of active sulfur and capacity decline.
Correct answer is: Polysulfide shuttle effect causing active material loss
Q.102 Which of the following statements about the 'energy‑power triangle' is correct?
A battery can simultaneously maximize energy density, power density, and cycle life without trade‑offs.
Improving energy density usually reduces power density or cycle life.
Power density is independent of energy density.
Cycle life does not affect either energy or power density.
Explanation - Design trade‑offs mean that increasing one metric often compromises another (e.g., high energy ↔ lower power or life).
Correct answer is: Improving energy density usually reduces power density or cycle life.
Q.103 Which of the following is a typical symptom of a failing battery cell in a series pack?
All cells show the same voltage
One cell voltage deviates significantly from the others
Battery temperature drops below ambient
Pack voltage increases while under load
Explanation - A weak cell will have a lower voltage, causing imbalance and potentially limiting pack performance.
Correct answer is: One cell voltage deviates significantly from the others
Q.104 What is the primary function of a 'fuse' in a battery system?
To increase the voltage of the pack
To protect against over‑current conditions by breaking the circuit
To balance the state of charge among cells
To store additional energy
Explanation - A fuse interrupts current flow when it exceeds a predefined limit, safeguarding the system.
Correct answer is: To protect against over‑current conditions by breaking the circuit
Q.105 Which of the following battery chemistries is most commonly used for grid‑scale energy storage due to its long cycle life and low cost?
Lithium‑ion
Vanadium redox flow battery
Lead‑acid
Nickel‑metal hydride
Explanation - Vanadium redox flow batteries allow independent scaling of power and energy, offering long life and relatively low cost for stationary storage.
Correct answer is: Vanadium redox flow battery
Q.106 Which of the following is a typical characteristic of a 'lithium‑ion polymer' (Li‑poly) cell compared to a cylindrical Li‑ion cell?
Higher internal pressure
Rigid metal case
Flexibility in shape and size
Lower nominal voltage
Explanation - Li‑poly cells use flexible pouches, allowing manufacturers to design thin, lightweight batteries for slim devices.
Correct answer is: Flexibility in shape and size
Q.107 What is the typical voltage range of a single cell in a nickel‑cadmium (Ni‑Cd) battery?
0.9‑1.0 V
1.2‑1.3 V
2.0‑2.2 V
3.6‑3.7 V
Explanation - Ni‑Cd cells have a nominal voltage of about 1.2 V per cell.
Correct answer is: 1.2‑1.3 V
Q.108 Which of the following is NOT a typical method to increase the energy density of a battery cell?
Increasing the thickness of electrodes
Using higher voltage cathode materials
Reducing the mass of inactive components
Adding more separator material
Explanation - More separator adds dead weight/volume without storing energy, reducing energy density.
Correct answer is: Adding more separator material
Q.109 In battery terminology, the term "C‑rate" of 0.5 C means:
The battery will be fully charged in 0.5 hours
The battery will be discharged at half its nominal capacity per hour
The battery voltage is half of its nominal value
The battery is operating at half its maximum temperature
Explanation - 0.5 C indicates a current that would fully discharge the battery in 2 hours (1 ÷ 0.5 = 2).
Correct answer is: The battery will be discharged at half its nominal capacity per hour
Q.110 Which of the following is a major advantage of using a 'bypass diode' across a solar‑panel‑connected battery charger?
It allows the battery to charge faster
It prevents reverse current flow from the battery to the panel at night
It increases the voltage of the solar panel
It balances the cells in the battery pack
Explanation - A bypass diode blocks the battery from discharging back into the solar panel when there is no sunlight.
Correct answer is: It prevents reverse current flow from the battery to the panel at night
Q.111 Which of the following battery chemistries suffers from the "memory effect" if not fully discharged periodically?
Lithium‑ion
Nickel‑cadmium
Lead‑acid
Sodium‑sulfur
Explanation - Ni‑Cd batteries lose capacity if they are repeatedly partially discharged without a full discharge cycle.
Correct answer is: Nickel‑cadmium
Q.112 Which of the following is a typical characteristic of a 'flow battery' compared to conventional solid‑state batteries?
Energy storage is limited by the size of the cell stack only
Energy capacity can be increased simply by enlarging the electrolyte tanks
They have higher energy density than Li‑ion batteries
They cannot be recharged
Explanation - In flow batteries, the electrolyte volume determines stored energy, allowing modular scaling.
Correct answer is: Energy capacity can be increased simply by enlarging the electrolyte tanks
Q.113 What is the typical self‑discharge rate of a high‑quality lithium‑ion cell per month?
Less than 1 %
5‑10 %
15‑20 %
Over 30 %
Explanation - Good Li‑ion cells self‑discharge at about 0.5‑1 % per month under normal conditions.
Correct answer is: Less than 1 %
Q.114 Which of the following is a primary reason for using a 'current collector' in a battery electrode?
To store additional charge
To provide a low‑resistance path for electrons
To act as a separator
To regulate temperature
Explanation - Current collectors (e.g., copper for anodes, aluminium for cathodes) ensure efficient electron transport to/from the external circuit.
Correct answer is: To provide a low‑resistance path for electrons
Q.115 Which of the following statements about 'over‑voltage protection' in a BMS is FALSE?
It disconnects the pack when cell voltage exceeds a safe limit.
It prevents lithium plating during charging.
It allows the battery to be charged beyond its rated voltage safely.
It protects against cell degradation.
Explanation - Over‑voltage protection is intended to **prevent** charging beyond safe limits, not permit it.
Correct answer is: It allows the battery to be charged beyond its rated voltage safely.
Q.116 The term 'specific power' (W/kg) of a battery is most critical for which application?
Electric vehicle range
Power tools requiring short bursts of high power
Stationary grid storage
Low‑drain remote sensors
Explanation - High specific power enables rapid energy delivery, essential for tools that need quick, intense power output.
Correct answer is: Power tools requiring short bursts of high power
Q.117 Which of the following best describes the function of a 'thermal management system' in a battery pack?
Regulates the state of charge
Maintains temperature within safe operating limits
Increases the nominal voltage
Provides mechanical support
Explanation - Thermal management (cooling/heating) ensures the battery operates within its optimal temperature range, preventing degradation and safety issues.
Correct answer is: Maintains temperature within safe operating limits