Battery Types and Operations Introduction

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.

Explore the different types of batteries, including primary and secondary batteries, and understand their requirements. This quiz will also cover the basic operation of batteries, focusing on key components such as electrodes and electrolytes. Test your knowledge on how batteries work and their applications.