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What is the purpose of the battery in a car?

ELECTRICAL I LESSON 1 THE AUTOMOTIVE BATTERY. What is the purpose of the battery in a car?. Provide voltage and current for the starter motor

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What is the purpose of the battery in a car?

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  1. ELECTRICAL I LESSON 1 THE AUTOMOTIVE BATTERY

  2. What is the purpose of the battery in a car? • Provide voltage and current for the starter motor • Provide voltage and current for the ignition system during cranking • Supplies all electrical power when the charging system is not operating • Acts as a voltage stabilizer for the charging system • Provides extra current for short periods of time while the charging system is catching up to a new load

  3. BATTERY OPERATION • The automotive battery is an electrochemical device that provides a potential difference. • Automotive batteries are made up of a series of secondary cells that can be recharged. • The battery does not store electrical energy, it stores chemical energy that is converted to electrical energy as it discharges.

  4. What is needed for an electrochemical reaction to occur? • Two unlike metals in a conductive and reactive solution (electrolyte) • A battery cell is made up of spongy lead, lead peroxide and an electrolyte of sulfuric acid and water. • This kind of battery is called a lead-acid battery. • The spongy lead (Pb) is the negative material. • The lead peroxide (PbO2) is the positive material. • The electrolyte is 64% water (H2O) and 36% sulfuric acid (H2SO4) when the battery is fully charged.

  5. The Discharge – Charge Process • As the battery discharges, a chemical reaction occurs which releases electrons from the lead (Pb) and causes the lead peroxide (PbO2) to gain electrons. • During this process both of the materials are changing to lead sulfate (PbSO4) and the electrolyte’s acid is changing to water (H2O). • As the battery is recharged the reaction is reversed and the materials and electrolyte return to their original states.

  6. The process of discharging and recharging is calledcycling. • Discharging Reaction: • Pb + H2SO4Þ PbSO4 + H2 + 2 electrons • PbO2 + H2SO4 + 2 electrons Þ PbSO4 + H2O + O2 • Recharging Reaction: • PbSO4 + 2 electrons + H2ÞPb + H2SO4 • PbSO4 (-2 electrons) + H2O + O2Þ PbO2 + H2SO4

  7. Voltage • Each battery cell produces 2.1v during the discharge reaction. • Cells are connected in series to gain the desired battery voltage. • 3 cells yield 6.3v • 6 cells yield 12.6v • Charging voltage needs to be 1 volt or more above battery voltage to reverse the reaction.

  8. Battery Construction: • Cells are made of positive and negative plates which are kept from touching by a porous separator material, usually plastic or fiberglass. • The plates are made on a lead alloy grid which holds the spongy lead or lead peroxide material. • The positive grids are connected together with a post strap. The negative grids are also connected together. The grids carry the cell current to the battery posts. • The battery case is divided into cell cavities which hold the electrolyte and the plate groups. The plate group from one cell is connected to another cell’s plate group through a hole in the cell wall.

  9. Battery Varieties • Cycling Battery – • Designed to produce low current for long periods of time. • They are usually very discharged before recharging. • Plate material is thicker than an automotive battery. • Starting Battery – • Designed to produce high current for very short periods of time. • There is usually only a slight discharge before recharging. • Plate material is thinner to reduce heat generation.

  10. Battery Types: • 1. Non-maintenance Free - • Lead-antimony grid • Removable vent caps use to inspect electrolyte and add water. • 2. Low-maintenance - • Hidden vent caps • Lead - calcium or Lead - strontium grid which lowers electrical resistance and heat generation. This reduces gassing and electrolyte loss.

  11. Battery Types: • 3. Maintenance Free - • No vent caps. The case has small vents at both ends. • Grid similar to low-maintenance • Envelope type separators keep loose plate material near plates

  12. Battery Types: • 4. Hybrid – • Lead - antimony in positive grid, • Lead - calcium in negative grid reduces gassing and internal corrosion • Spun glass separators allow for a more efficient chemical reaction • These batteries are able to withstand more deep cycling

  13. Battery Types: • 5. Recombinant – • No caps or vents • Gel type electrolyte • Special envelope type separators allow hydrogen gas to be reabsorbed. No gassing • Generate 13.2 volts with six cells

  14. Grid Types • 1. Square Grid – • The grid frame is a pattern of squares or rectangles. • Longer current path, high resistance • 2. Diagonal Grid – • The vertical grid bars are set at diagonals to shorten • the current path and lower resistance

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