The lead acid battery was invented in 1859 by French physicist Gaston Planté and is considered as one of the oldest type of rechargeable battery. Planté invented it by depositing lead oxide on both sides of a lead sheet and using a diluted sulfuric acid as electrolyte in between the plates. This setup had lead plates acting as both positive and negative electrodes and thus formed the world's first practical secondary battery. Since its invention, the rechargeable battery has undergone multiple advancements and today it is one of the most widely used rechargeable batteries globally.
Design and Working Principle
A typical rechargeable battery consists of positive and negative plates suspended in a electrolyte solution of diluted sulfuric acid. The positive plates are made of lead dioxide (PbO2) while the negative plates are made of spongy lead (Pb). These plates are immersed in the electrolyte solution, usually a dilute sulfuric acid solution (H2SO4), and connected externally through terminals. During discharging, the lead plates chemically react with the sulfuric acid and undergo oxidation-reduction reactions to produce direct current. When charging, this process is reversed with current flowing in the opposite direction, restoring the materials to their original state.
When the Lead Acid Battery is being discharged, lead (Pb) of the negative plate reacts with sulfate ions (SO4--) from the electrolyte to form lead sulfate (PbSO4) and liberate electrons (e-). At the same time, lead dioxide (PbO2) of the positive plate reacts with hydrogen ions (H+) from the electrolyte to form lead sulfate (PbSO4) along with consuming electrons. This causes the lead sulfate to accumulate on both plates. During charging, these processes are reversed as the lead sulfate on the plates converts back to lead (Pb) and lead dioxide (PbO2) with the help of an external electrical source.
Applications
Due to its rugged design, affordability and ease of maintenance, rechargeable battery find applications in a variety of industries. Automotive is one of the major application areas where they are used as starter batteries in vehicles to provide instant power required for cranking the engine. Telecom industry also uses them extensively as backup power in case of grid failures or emergencies. Industrial UPS, controls systems and welding equipment also employ rechargeable battery as a reliable and cost-effective power source. Their suitability for deep discharge cycles makes them popular for motive power applications like electric forklifts, aerial lifts, mobile machinery etc. Microgrids and renewable energy systems also incorporate rechargeable battery for energy storage and management. Their availability in different form factors allows use in a variety of equipment ranging from household emergency lights, motorcycles, boats, tractors, portable electronics and more.
Types of Lead Acid Battery
Based on the construction and internal design, rechargeable battery are available in different types suitable for diverse applications:
- Flooded batteries: Traditionally used battery type where the lead plates are immersed directly in liquid electrolyte for maximum current delivery. Require periodic maintenance like topping up electrolyte levels.
- VRLA batteries: VRLA stands for valve regulated lead acid. These sealed batteries have immobilized electrolyte gel or AGM that eliminates electrolyte spillage issues. Used where maintenance-free operation is required.
- Stationary batteries: Large capacity batteries commonly used for UPS, telecom towers, renewable energy storage etc where high power and energy density is required.
- SLI batteries: SLI stands for starting, lighting and ignition. Commonly known as automotive or car batteries used to start the vehicle engine.
- MF/VRLA batteries: Modified Flooded or valve regulated rechargeable battery for stationary applications having thin plates for deep cycling.
- Synthetic gel batteries: Use an environment-friendly synthetic electrolyte gel instead of liquid electrolyte for higher performance.
Advantages
- High reliability: Lead acid battery are very durable and can complete hundreds of charge-discharge cycles over their lifetime of 3-5 years.
- Cost effectiveness: Compared to newer battery technologies, rechargeable battery have very low initial as well as overall operational cost.
- Easy maintenance: Flooded versions can be topped up easily with distilled water as required. VRLA batteries have almost no maintenance needs.
- Wide operating temperature: Can function between -50°C to 60°C, making them suitable for diverse climatic conditions.
- Recyclability: Over 99% of their materials can be recycled at the end of life, making them highly eco-friendly.
- Abundantly available: Lead and sulfuric acid used in them are abundantly available as raw materials globally.
- Simple design: Easy to manufacture due to simple chemical reactions and design that has remained unchanged for over 150 years.
While rechargeable battery may not match the high energy densities of newer battery chemistries, their reliability, robustness, maintenance-free operation and affordable cost has sustained their popularity, especially for stationary and automotive applications. Continuous improvements in electrode materials, electrolyte constitution and manufacturing have ensured that rechargeable battery will remain one of the major battery technologies for years to come.
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