Lead-acid batteries are the oldest rechargeable battery technology, still widely used today. They come in two main types: flooded cell and valve-regulated lead-acid (VRLA). Each has unique characteristics, making them suitable for different applications.
Lead-acid batteries have low energy density but are reliable and cost-effective. They're commonly used in automotive, UPS systems, and deep cycle applications. Understanding their chemistry, design, and performance is crucial for optimizing their use in various energy storage scenarios.
Lead-Acid Battery Types and Design
Flooded Cell and VRLA Batteries
Top images from around the web for Flooded Cell and VRLA Batteries Batteries and Fuel Cells | Chemistry: Atoms First View original
Is this image relevant?
Lead Storage Battery | Introduction to Chemistry View original
Is this image relevant?
Batteries and Fuel Cells | Chemistry: Atoms First View original
Is this image relevant?
Lead Storage Battery | Introduction to Chemistry View original
Is this image relevant?
1 of 3
Top images from around the web for Flooded Cell and VRLA Batteries Batteries and Fuel Cells | Chemistry: Atoms First View original
Is this image relevant?
Lead Storage Battery | Introduction to Chemistry View original
Is this image relevant?
Batteries and Fuel Cells | Chemistry: Atoms First View original
Is this image relevant?
Lead Storage Battery | Introduction to Chemistry View original
Is this image relevant?
1 of 3
Flooded cell lead-acid batteries contain liquid electrolyte that can move freely within the battery case
Require regular maintenance, including topping up the electrolyte level with distilled water
Prone to spillage if not handled properly (stationary applications)
Valve-regulated lead-acid (VRLA) batteries have a sealed design with a pressure relief valve
Electrolyte is immobilized in a gel or absorbed in a glass mat (AGM)
Maintenance-free and spill-proof, making them suitable for portable applications (UPS systems, wheelchairs)
Higher cost compared to flooded cell batteries
Deep Cycle and Plate Design
Deep cycle lead-acid batteries are designed for repeated deep discharges (up to 80% depth of discharge)
Thicker plates and higher active material density compared to starter batteries
Used in applications requiring long-term energy storage (solar power systems, golf carts)
Plate design affects battery performance and longevity
Flat plates are simple and cost-effective but have limited surface area
Tubular plates have higher surface area and improved cycle life but are more expensive to manufacture
Grid alloys, such as lead-calcium and lead-antimony, influence battery characteristics
Lead-calcium alloys reduce water loss and self-discharge but have lower cycle life
Lead-antimony alloys improve deep cycling performance but increase water loss and maintenance requirements
Energy Density and Self-Discharge
Specific energy of lead-acid batteries ranges from 30-50 Wh/kg
Lower than other rechargeable battery technologies (Li-ion, NiMH)
Limits their use in weight-sensitive applications (portable devices)
Energy density of lead-acid batteries is approximately 60-110 Wh/L
Requires larger battery sizes for high-energy applications (electric vehicles)
Self-discharge rate of lead-acid batteries is relatively low, typically 3-5% per month at room temperature
Increases with rising temperature and battery age
Regular charging is necessary to maintain full capacity
Charge-Discharge Cycle and Sulfation
Charge-discharge cycle efficiency of lead-acid batteries is around 70-80%
Energy losses occur due to internal resistance and heat generation
Proper charging algorithms (constant current-constant voltage) can optimize efficiency
Sulfation is a common failure mode in lead-acid batteries
Occurs when lead sulfate crystals grow and accumulate on the plates during prolonged periods of low charge
Reduces battery capacity and increases internal resistance
Regular charging and occasional equalization charges can help prevent sulfation
Lead-Acid Battery Applications
Automotive and UPS Systems
Automotive applications are the most common use for lead-acid batteries
Starting, lighting, and ignition (SLI) batteries provide high current for engine starting
Deep cycle batteries power electric vehicles (forklifts, golf carts)
Low cost and reliable performance make them the preferred choice for vehicles
Uninterruptible power supply (UPS) systems rely on lead-acid batteries for backup power
Provide continuous power during utility outages to critical loads (data centers, hospitals)
VRLA batteries are commonly used due to their maintenance-free and spill-proof design
Long service life and high reliability are essential for UPS applications
Lead-Acid Battery Electrolyte
Electrolyte Composition and Concentration
The electrolyte in lead-acid batteries is a mixture of sulfuric acid (H2SO4) and water
Sulfuric acid is the active component that participates in the electrochemical reactions
Water acts as a solvent and helps in ionic conductivity
Electrolyte concentration, measured in terms of specific gravity, varies during charge and discharge
Fully charged battery has a specific gravity of around 1.28
Specific gravity decreases during discharge as sulfuric acid is consumed
Electrolyte concentration affects battery performance and freezing point
Higher concentration improves capacity but increases the risk of sulfation and decreases the freezing point
Lower concentration reduces capacity but improves low-temperature performance
Proper electrolyte maintenance, including regular specific gravity checks and adjustments, is crucial for optimal battery performance and longevity