AEE_Unit_II

Unit II: STORAGE BATTERIESLead Acid BatteryClassification: Rechargeable and secondary batteries.Characteristics: Offers high surge currents despite low energy-to-volume and energy-to-weight ratios. Utilizes lead peroxide and sponge lead for energy conversion.Applications: Widely used in substations and power systems due to their higher cell voltage levels and low cost.

ConstructionKey Components:

• Container

• Plates

• Active Component

• Separators

• Battery Edges(Illustration of lead acid battery components)

1. Container

   • Made from materials like: Ebonite, Lead-coated wood, Glass, Hard rubber, Ceramic materials, Forged plastic.

   • Features: Rigid design with four ribs on the bottom to support plates and prevent short-circuiting. Components must be resistant to sulfuric acid and must be free from impurities.

2. Plates

   • Constructed from grids of active components and lead. Important for electrical conductivity.

   • Types of Plates:

     • Plante/formed plates: Used mainly in static batteries. Heavier and more expensive but durable. Minimal active component loss during use.

     • Faure/pasted plates: Predominantly used for negative plates. Complex structure when discharging and charging.

3. Active Component

   • Engaged in chemical reactions during charging and discharging.

   • Components:

     • Lead Peroxide: Positive active component

     • Sponge Lead: Negative active component

     • Diluted Sulfuric Acid: Serves as the electrolyte.

4. Separators

   • Thin, porous sheets made of rubber and glass fiber.

   • Function: Provide insulation between plates and shaped for efficiency (grooved on one side).

5. Battery Edges

   • Positive and negative terminals have diameters of 17.5 mm and 16 mm, respectively.

Working PrincipleElectrolyte Reaction: Sulfuric acid dissociates into negative (SO4-) and positive (2H+) ions. Movement of ions contributes to energy transfer: Positive ions move towards the negative edge. Negative ions move towards the positive edge.Reactions:

• Hydrogen and sulfate ions interact with water, forming hydrogen and sulfuric acid.

• Lead oxide reacts to form lead peroxide when charging.

Charging and Discharging

• Charging Process: Lead cathode remains lead; lead anode forms dark brown lead peroxide.

• Discharging Process: Current flows from negative to positive plate when connected, indicating energy provision.

Types of Lead Acid Batteries

• Flooded Type: Conventional battery; users can access cells to add water.

• Sealed Type: No access to cells; designed to contain enough acid for battery life.

• VRLA Type: Valve Regulated Lead Acid; safely manages gas evolution during charging.

• AGM Type: Absorbed Glass Matte; suitable for power sports and engine starting.

• Gel Type: Stiffened electrolyte; less voltage sensitivity.

Life and Longevity

• Optimal operating temperature is 25°C (77°F).

• Life expectancy decreases with higher temperatures: 10 years at 25°C, 5 years at 33°C.

Applications of Lead Acid BatteriesCommon uses include:

• Emergency lighting

• Electric motors

• Submarines and nuclear submarines.

Nickel-Cadmium (NiCd) BatteryProduces DC voltage from a chemical reaction between nickel and cadmium.

• Voltage output: Approximately 1.2 V.

• Cells typically wired in series to achieve higher voltages (3.6 to 4.8 V).

Construction of NiCd BatteryConsists of nickel and cadmium layers with a separator layer of KOH or NaOH. Inner layers facilitate the effective chemical reaction needed for current generation.

Battery Voltage and Performance Parameters

• Runtime temperature:

  • Charging: 0°C to 45°C

  • Discharging: -20°C to 65°C

• Toxicity risk from cadmium; impacts human health.

• Voltage: around 1.2 V with higher specific energy than nickel-iron batteries.

Working Principle of NiCd BatteryChemical reactions occur between cadmium, nickel, and separator ions. Electrodes interact with electrolytes to generate voltage.

Types of NiCd BatteriesClassified based on size (e.g., AAA, AA) and voltage output.

Advantages and Disadvantages of NiCd BatteriesAdvantages:

• High current output

• Overcharging tolerance

• Up to 500 charge cycles.

Disadvantages:

• Non-eco-friendly cadmium

• Lower temperature tolerance.

Battery Charging Regimens

• Constant Voltage Charging: Engine-driven generators supply voltage directly to batteries. Voltage control prevents overheating and battery failure.

• Constant Current Charging: Efficient for charging multiple batteries simultaneously. Specific charging practices to maximize battery life and electrolyte levels.

Capacity Check and Maintenance Practices

• Capacity measured in ampere-hours at specific voltages. Maintenance procedures must conform to manufacturer specifications for health checks.

Aircraft Battery MaintenanceConsists of thorough inspections for electrolyte levels, corrosion, and connection integrity.

Storing and Service FacilitiesStrict separation required when storing different battery types to prevent contamination.

Battery Freezing PreventionDischarged lead-acid batteries are susceptible to freezing damage. Maintain specific gravity above 1.275.

Troubleshooting GuidelinesIdentify common battery issues such as capacity loss and electrolyte leakage. Conduct corrective measures based on specific problems.

Ground Power UnitsBattery-powered generators that supply power to aircraft on the ground. Designed to be compatible with a variety of aircraft electrical systems.

Aircraft Electrical Systems and OperationsKey functions include starters, lights, and navigation systems. GPUs provide necessary electrical energy before flight.

Ground Support Equipment (GSE)Essential for aircraft operational readiness: Includes cleaning, maintenance, and passenger safety procedures. Equipment diversity for effective aircraft servicing.