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Questions and Answers
Which of the following is NOT a requirement of a secondary battery?
Which of the following is NOT a requirement of a secondary battery?
- Short time for a recharge
- Long shelf-life in both charged & discharged conditions
- High power to weight ratio
- Compact and lightweight (correct)
What differentiates battery reactions from other oxidation/reduction processes?
What differentiates battery reactions from other oxidation/reduction processes?
- The physical separation of the oxidation and reduction reactions (correct)
- The interaction of gas rather than liquid components
- The presence of the same chemical reactions occurring in parallel
- The use of a single electrode for both reactions
Which component of a battery is primarily responsible for transferring electrons during the redox reaction?
Which component of a battery is primarily responsible for transferring electrons during the redox reaction?
- Electrode (correct)
- Separator
- Insulator
- Electrolyte
What type of reactions do lead-acid and alkaline batteries utilize in their operation?
What type of reactions do lead-acid and alkaline batteries utilize in their operation?
What characteristic of a primary battery is emphasized in its requirements?
What characteristic of a primary battery is emphasized in its requirements?
Which of the following correctly states a requirement for secondary batteries?
Which of the following correctly states a requirement for secondary batteries?
In battery operation, the exchange of electrons corresponds to which of the following?
In battery operation, the exchange of electrons corresponds to which of the following?
What is the primary function of the electrolyte in a battery?
What is the primary function of the electrolyte in a battery?
What must be minimized to derive maximum voltage from a battery?
What must be minimized to derive maximum voltage from a battery?
Which factor does not contribute to the capacity of a battery?
Which factor does not contribute to the capacity of a battery?
What is current a measure of in a battery system?
What is current a measure of in a battery system?
In the expression for battery capacity, what does 'C' represent?
In the expression for battery capacity, what does 'C' represent?
To achieve efficient discharge, which property of the electrolyte is preferred?
To achieve efficient discharge, which property of the electrolyte is preferred?
What happens when a battery reaches its minimum voltage during discharge?
What happens when a battery reaches its minimum voltage during discharge?
Which design consideration helps minimize internal resistance in a battery?
Which design consideration helps minimize internal resistance in a battery?
What occurs to the viscosity of the electrolyte when the temperature decreases?
What occurs to the viscosity of the electrolyte when the temperature decreases?
What is the effect of overpotentials on battery performance?
What is the effect of overpotentials on battery performance?
What may occur if a battery is overcharged?
What may occur if a battery is overcharged?
What is a primary cause of lead acid battery failure?
What is a primary cause of lead acid battery failure?
Why should safety goggles be worn when working with batteries?
Why should safety goggles be worn when working with batteries?
Which material is used for the positive electrode in nickel-metal hydride (NiMH) batteries?
Which material is used for the positive electrode in nickel-metal hydride (NiMH) batteries?
What distinguishes NiMH batteries in terms of energy density compared to Ni-Cd batteries?
What distinguishes NiMH batteries in terms of energy density compared to Ni-Cd batteries?
What is the main material used in the negative electrode of NiMH batteries?
What is the main material used in the negative electrode of NiMH batteries?
How are the positive and negative plates arranged in cylindrical NiMH batteries?
How are the positive and negative plates arranged in cylindrical NiMH batteries?
What happens to hydrogen in hydrogen-absorbing alloys during charge?
What happens to hydrogen in hydrogen-absorbing alloys during charge?
Which type of alloy is particularly noted for its discharge efficiency and durability in battery applications?
Which type of alloy is particularly noted for its discharge efficiency and durability in battery applications?
What is a key characteristic of nickel-metal hydride batteries during reactions?
What is a key characteristic of nickel-metal hydride batteries during reactions?
What happens to the cobalt ions during the charging process of the battery?
What happens to the cobalt ions during the charging process of the battery?
What is the primary function of the hydrogen-absorbing alloy negative electrode?
What is the primary function of the hydrogen-absorbing alloy negative electrode?
Which of the following is a major advantage of lithium-ion batteries compared to other types?
Which of the following is a major advantage of lithium-ion batteries compared to other types?
What distinguishes NiMH batteries from traditional nickel-cadmium batteries?
What distinguishes NiMH batteries from traditional nickel-cadmium batteries?
What is typically used as the electrolyte in nickel-metal hydride batteries?
What is typically used as the electrolyte in nickel-metal hydride batteries?
During discharge, what state do the lithium ions migrate to?
During discharge, what state do the lithium ions migrate to?
Which of the following is NOT a type of hydrogen-absorbing alloy mentioned?
Which of the following is NOT a type of hydrogen-absorbing alloy mentioned?
What is the average voltage equivalent of a lithium-ion battery compared to nickel-cadmium cells?
What is the average voltage equivalent of a lithium-ion battery compared to nickel-cadmium cells?
What is one significant limitation of lithium-ion batteries?
What is one significant limitation of lithium-ion batteries?
During the process of sealing a battery, what is maintained constant within the battery?
During the process of sealing a battery, what is maintained constant within the battery?
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Study Notes
Battery Types
- Rechargeable batteries are also known as storage cells or accumulators, including lead-acid, nickel-cadmium, and lithium-ion batteries.
Requirements of Battery Types
- Primary Batteries: Should be compact, lightweight, economical, have benign environmental properties, high energy density, longer shelf life, provide constant voltage, and long discharge periods.
- Secondary Batteries: Need long shelf life in both charged and discharged conditions, longer cycle life, high power-to-weight ratio, quick recharge times, high voltage, and high energy density.
Basic Battery Operation
- Batteries operate through electron exchange between oxidation and reduction reactions, which are physically separated to allow for a load to be connected.
- The electrochemical potential difference corresponds to the battery voltage, while electron flow represents current.
Key Components
- Must include electrodes (site of electron transfer) and electrolytes (medium for ion exchange).
- Internal resistance, electrode materials, and electrolyte conductivity are critical for maximizing battery performance.
Cell Potential Equation
- The battery voltage (cell potential) is calculated with the formula:
- Cell potential = (EC - EA) - |ηA - ηC| - i Rcell
- Maximize voltage by ensuring high electrode potential difference, fast reaction rates, and low internal resistance.
Current and Capacity
- Current reflects the uniform flow of electrons and is measured in amperes per second.
- Battery capacity is measured in ampere-hours (Ah) and is influenced by the size, active material mass, and discharge conditions.
Safety Considerations
- Electrolyte conductivity is crucial; decreased temperature raises viscosity and lowers potential.
- Overcharging can damage electrodes and lead to explosions, necessitating safety precautions, especially when handling corrosive materials like sulfuric acid.
Nickel-Metal Hydride (NiMH) Batteries
- Developed to provide higher energy densities and support sophisticated electronic devices.
- Constructed with nickel hydroxide positive plates and hydrogen-absorbing alloys for the negative side.
Hydrogen-Absorbing Alloys
- Capable of absorbing hydrogen up to a thousand times their volume while facilitating efficient charge and discharge cycles.
- Classified into AB, AB2, AB5, and A2B types based on metal combinations.
NiMH Battery Characteristics
- NiMH batteries offer about twice the energy density of Ni-Cd batteries with similar operating voltages.
- Charging and discharging involve the movement of hydrogen ions without altering the electrolyte composition.
Advantages of NiMH Batteries
- Higher energy density and capacity (1000mAh to 3000mAh).
- Safer and environmentally friendly compared to older technologies.
Lithium-Ion Batteries
- Designed to address safety issues related to lithium metal.
- Long cycle life (400-1200 cycles) and greater energy density than nickel-based batteries.
- Can recharge before full discharge, optimized for internal device charging.
Limitations of Lithium-Ion Batteries
- Prone to poor charge retention with a self-discharge rate of approximately 10% per month.
- Higher manufacturing costs compared to some alternatives.
Performance Comparison
- A typical lithium-ion battery can store 150 watt-hours per kilogram, in contrast to lead-acid batteries' 25 watt-hours per kilogram.
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