lead acid battery

lead acid battery

1. TOPIC: Lead-acid battery

2. History: The  lead – acid battery  was invented in 1859 by French physicist Gaston Planté It is the oldest type of rechargeable  battery ( by passing a reverse current through it ). As they are inexpensive compared to newer technologies,  lead – acid batteries  are widely used even when surge current is not important and other designs could provide higher energy densities . This battery uses a gel electrolyte instead of a liquid allowing the battery to be used in different positions without leaking.

3. Lead-acid battery: construction Pb PbO 2 H 2 O H 2 SO 4 Positive electrode: Lead-dioxide Negative electrode: Porous lead Electrolyte: Sulfuric acid, 6 molar • How it works Characteristics and models Charge controllers

4. Electrical conduction mechanisms Lead and lead-dioxide are good electrical conductors . The conduction mechanism is via electrons jumping between atoms. The electrolyte contains aqueous ions (H + and SO 4 -2 ). The conduction mechanism within the electrolyte is via migration of ions via diffusion or drift. Pb PbO 2 H 2 O SO 4 -2 SO 4 -2 H + H + H + H +

5. Conduction mechanism at the surface of the electrode Oxidation-reduction (Redox) reaction transfers charge from ions in solution to conducting electrons in the electrode At the surface of the lead (negative) electrode: Pb Pb Pb Pb Pb Pb Pb SO 4 -2 SO 4 -2 H + H + H + H + H 2 O Lead electrode Sulfuric acid electrolyte Pb Pb Pb Pb +2 Pb Pb Pb SO 4 -2 SO 4 -2 H + H + H + H + H 2 O Lead electrode Sulfuric acid electrolyte – –

6. How the battery develops voltage Pb PbO 2 SO 4 -2 H 2 O Pb Pb Pb Pb +2 Pb Pb Pb SO 4 -2 SO 4 -2 H + H + H + H + H 2 O SO 4 -2 SO 4 -2 H + H + H + H + H 2 O Pb +4 O –2 O –2 Pb +4 O –2 O –2 Pb +4 O –2 O –2 – – – – Consider the following experiment: New electrodes are placed inside electrolyte, with no external electrical circuit connected The reactions start to occur They use up aqueous ions nearelectrodes Diffusion within electrolytereplenishes ions near electrodes Excess electrons are created inlead electrode, and electron deficit is created in lead-dioxide electrode Electric field is generated at electrode surfaces. This electric field opposes the flow of ions.

7. Types of lead-acid batteries Car battery “SLI” - starter lighting ignition Designed to provide short burst of high current Maybe 500 A to crank engine Cannot handle “deep discharge” applications Typical lifetime of 500 cycles at 20% depth of discharge Deep discharge battery We have these in power lab carts More rugged construction Bigger , thicker electrodes Calcium (and others) alloy: stronger plates while maintaining low leakage current More space below electrodes for accumulation of debris before plates are shorted Ours are Sealed, valve regulated, absorbent glass mat Rated 56 A-hr at 2.33A (24 hr) discharge rate

8. “Golf cart” or “forklift” batteries Similar to #2 Bigger, very rugged Low cost — established industry Antimony alloy Strong big electrodes But more leakage current than #2 Can last 10-20 years Manufacturer’s specifications for our power lab batteries: Nominal capacity: A-hrs @ 25 ˚ C to 1.75 V/cell A-hr 36 1 hr A-hr 56 49 A-hr 46 A-hr 45 A-hr hr 24 hr 8 hr 4 2 hr Types of lead-acid batteries

9. Applications Automotive and traction applications. Standby/Back-up/Emergency power for electrical installations. Submarines UPS (Uninterruptible Power Supplies) Lighting High current drain applications. Sealed battery types available for use in portable equipment.

10. Advantages Low cost. Reliable. Over 140 years of development. Robust. Tolerant to abuse. Tolerant to overcharging. Low internal impedance. Can deliver very high currents. Indefinite shelf life if stored without electrolyte. Can be left on trickle or float charge for prolonged periods. Wide range of sizes and capacities available. Many suppliers world wide. The world's most recycled product.

11.  Disadvantages Dangers from Chemical Burns Batteries Can Be Heavy Flammable Gases While Charging Electrolyte Can Evaporate

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