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OBJECTIVES

OBJECTIVES. After studying Chapter 16, the reader should be able to: Prepare for ASE Electrical/Electronic Systems (A6) certification test content area (Battery Diagnosis and Service). Describe how a battery works. List battery ratings. Describe deep cycling.

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OBJECTIVES

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  1. OBJECTIVES After studying Chapter 16, the reader should be able to: • Prepare for ASE Electrical/Electronic Systems (A6) certification test content area (Battery Diagnosis and Service). • Describe how a battery works. • List battery ratings. • Describe deep cycling. • Discuss how charge indicators work.

  2. PURPOSE OF A BATTERY • Everything electrical in a vehicle is supplied current from the battery. • The battery is one of the most important parts of a vehicle because it is the heart or foundation of the electrical system.

  3. BATTERY CONSTRUCTION • Most automotive battery cases (container or covers) are constructed of polypropylene, a thin (approximately 0.08 in. [0.02 mm]thick), strong, and lightweight plastic. • Built into the bottom of many batteries are ribs that support the lead-alloy plates and provide a space for sediment to settle, called the Sediment Chamber.

  4. BATTERY CONSTRUCTION FIGURE 16-1 A typical polypropylene plastic battery case.

  5. GRIDS • Each positive and negative plate in a battery is constructed on a framework, or grid, made primarily of lead. FIGURE 16-2 The grid provides support for the plate active material.

  6. GRIDSMaintenance-Free versus Standard Battery Grids • Maintenance-free batteries use calcium instead of antimony, because 0.2% calcium has the same strength as 6% antimony. • Low-maintenance batteries use a low percentage of antimony(about 2% to 3%), or use antimony only in the positive plates and calcium for the negative plates.

  7. GRIDSRadial-Grid Design • Some batteries use a grid design with only vertical and horizontal strips. • The current must move over and up along the grid strips to reach point A. FIGURE 16-3 Current created at point B must travel to point A to be able to reach the battery terminals.

  8. GRIDSRadial-Grid Design • With a radial grid design (radial means branching out from a common center), the current generated near point B can travel directly to point A. FIGURE 16-4 Radial design battery grids permit lower resistance for current flow by joining the branches of the grids.

  9. GRIDSPositive Plates • The positive plates have lead dioxide (peroxide) placed onto the grid framework. • This active material can react with the sulfuric acid of the battery and is dark brown in color.

  10. GRIDSNegative Plates • The negative plates are pasted with a pure porous lead,called sponge lead, and are gray in color.

  11. GRIDS Separators • The positive and the negative plates must be installed alternately next to each other without touching. • Many batteries use envelope-type separators that encase the entire plate and help prevent any material that may shed from the plates from causing a short circuit between plates at the bottom of the battery.

  12. GRIDSCells • Cells are constructed of positive and negative plates with insulating separators between each plate. • Most batteries use one more negative plate than positive plate in each cell. FIGURE 16-5 Two groups are interlaced to form a battery element.

  13. GRIDSPartitions • Each cell is separated from the other cells by partitions,which are made of the same material as that used for the outside case of the battery. FIGURE 16-6 A cutaway battery showing the connection of the cells to each other through the partition.

  14. GRIDSElectrolyte • The electrolyte used in automotive batteries is a solution (liquid combination) of 36% sulfuric acid and 64% water. • This electrolyte is used for both lead-antimony and lead-calcium(maintenance-free) batteries.

  15. HOW A BATTERY WORKS • A fully charged lead-acid battery has a positive plate of lead dioxide (peroxide) and a negative plate of lead surrounded by a sulfuric acid solution (electrolyte).

  16. HOW A BATTERY WORKSDuring Discharging • The positive plate lead dioxide (PbO2) combines with the SO4, forming PbSO4 from the electrolyte and releases its O2 into the electrolyte, forming H2O. FIGURE 16-7 Chemical reaction for a lead-acid battery that is fully charged being discharged by the attached electrical load.

  17. HOW A BATTERY WORKSThe Fully Discharged State • When the battery is fully discharged, both the positive and the negative plates are PbSO4 (lead sulfate) and the electrolyte has become water (H2O).

  18. HOW A BATTERY WORKSDuring Charging • During charging, the sulfate (acid) leaves both the positive and the negative plates and returns to the electrolyte, where it becomes normal-strength sulfuric acid solution. FIGURE 16-8 Chemical reaction for a lead-acid battery that is fully discharged being charged by the attached generator.

  19. SPECIFIC GRAVITY • The amount of sulfate in the electrolyte is determined by the electrolyte’s specific gravity, which is the ratio of the weight of a given volume of a liquid to the weight of an equal volume of water. FIGURE 16-9 As the battery becomes discharged, the specific gravity of the battery acid decreases.

  20. SPECIFIC GRAVITYCharge Indicators • Some batteries are equipped with a built-in state-of-charge indicator. • When the ball floats, it appears in the hydrometer’s sight glass, changing its color. FIGURE 16-10 Typical battery charge indicator. If the specific gravity is low (battery discharged), the ball drops away from the reflective prism. When the battery is charged enough, the ball floats and reflects the color of the ball (usually green) back up through the sight glass, and the sight glass is dark.

  21. SPECIFIC GRAVITY VERSUS STATE OF CHARGE AND BATTERY VOLTAGE • Values of specific gravity, state of charge, and battery voltage at 80°F (27°C) are given in the following list.

  22. VALVE REGULATED LEAD-ACID BATTERIES • There are two basic types of valve regulated lead-acid (VRLA), also called sealed valve-regulated (SVR) or sealed lead-acid (SLA), batteries.

  23. VALVE REGULATED LEAD-ACID BATTERIESAbsorbed glass mat (AGM). • The acid used in an absorbed glass mat (AGM) battery is totally absorbed into the separator, making the battery leak-proof and spill proof. FIGURE 16-11 An absorbed glass mat battery is totally sealed and is more vibration resistant than conventional lead-acid batteries.

  24. VALVE REGULATED LEAD-ACID BATTERIESGelled electrolyte batteries. • In a gelled electrolyte battery, silica is added to the electrolyte, which turns the electrolyte into a substance similar to gelatin. • This type of battery is also called a gel battery.

  25. CAUSES AND TYPES OF BATTERY FAILURE • Most batteries have a useful service life of three to seven years; however, proper care can help increase the life of a battery, but abuse can shorten it. FIGURE 16-12 Battery that was accidentally left over the weekend on a battery charger that was set for a high charge rate. Note how the plates warped and the top blew off.

  26. BATTERY HOLD-DOWNS • All batteries must be attached securely to the vehicle to prevent battery damage. • Battery hold-down clamps or brackets help reduce vibration, which can greatly reduce the capacity and life of any battery.

  27. BATTERY RATINGS • Batteries are rated according to the amount of current they can produce under specific conditions.

  28. BATTERY RATINGSCold-Cranking Amperes • Every automotive battery must be able to supply electrical power to crank the engine in cold weather and still provide battery voltage high enough to operate the ignition system for starting.

  29. BATTERY RATINGSCranking Amperes • The designation CA refers to the number of amperes that can be supplied by a battery at 32°F (0°C). • This rating results in a higher number than the more stringent CCA rating.

  30. BATTERY RATINGSMarine Cranking Amperes • Marine cranking amperes (MCA) is similar to cranking amperes and is tested at 32°F (0°C).

  31. BATTERY RATINGSReserve Capacity • The reserve capacity rating for batteries is the number of minutes for which the battery can produce 25 amperes and still have a battery voltage of 1.75 volts per cell (10.5 volts for a 12 volt battery).

  32. BATTERY RATINGSAmpere Hour • Ampere hour is an older battery rating system that measures how many amperes of current the battery can produce over a period of time.

  33. DEEP CYCLING • Deep cycling is almost fully discharging a battery and then completely recharging it. • Charging is hard on batteries because the internal heat generated can cause plate warpage, so these specially designed batteries use thicker plate grids that resist warpage.

  34. BATTERY COUNCIL INTERNATIONAL GROUP SIZES • The Battery Council International (BCI) organization has established battery group size designations.

  35. BATTERY COUNCIL INTERNATIONAL GROUP SIZES

  36. BATTERY COUNCIL INTERNATIONAL GROUP SIZES

  37. WHAT CAN CAUSE A BATTERY TO EXPLODE? • Batteries discharge hydrogen gas and oxygen when being charged. If there happens to be a flame or spark, the hydrogen will burn. FIGURE 16-13 (a) A small spark inside the battery was the most likely cause of this battery explosion. Parts of the battery were thrown 30 ft (10 m); luckily, no one was around the vehicle at the time. (b) Because battery acid was spilled and sprayed around the battery, the entire area was rinsed with water after unplugging the battery charger.

  38. SUMMARY • Maintenance-free batteries use lead-calcium grids instead of lead-antimony grids to reduce gassing. • When a battery is being discharged, the acid (SO4) is leaving the electrolyte and being deposited on the plates. When the battery is being charged, the acid (SO4) is forced off the plates and back into the electrolyte. • Batteries are rated according to CCA and reserve capacity.

  39. REVIEW QUESTIONS • Explain why discharged batteries can freeze. • Identify the three most commonly used battery-rating methods. • Explain why a battery can explode if exposed to an open flame or spark.

  40. CHAPTER QUIZ • When a battery becomes completely discharged, both positive and negative plates become _____ and the electrolyte becomes _____. • H2SO4 /Pb • PbSO4 /H2O • PbO2 /H2SO4 • PbSO4 /H2SO4

  41. CHAPTER QUIZ 2. A fully charged 12 volt battery should indicate _____. • 12.6 volts or higher • A specific gravity of 1.265 or higher • 12 volts • Both a and b

  42. CHAPTER QUIZ 3. Deep cycling means _____. • Overcharging the battery • Overfilling or underfilling the battery with water • The battery is fully discharged and then recharged • The battery is overfilled with acid (H2SO4)

  43. CHAPTER QUIZ 4. What makes a battery “low maintenance” or “maintenance free”? • Alloy is used to construct the grids. • The plates are constructed of different metals. • The electrolyte is hydrochloric acid solution. • The battery plates are smaller, making more room for additional electrolytes.

  44. CHAPTER QUIZ 5. The positive battery plate is _____. • Lead dioxide • Brown in color • Sometimes called lead peroxide • All of the above

  45. CHAPTER QUIZ 6. Which battery rating is tested at 0°F (–18°C)? • Cold-cranking amperes (CCA) • Cranking amperes (CA) • Reserve capacity • Battery voltage test

  46. CHAPTER QUIZ 7. Which battery rating is expressed in minutes? • Cold-cranking amperes (CCA) • Cranking amperes (CA) • Reserve capacity • Battery voltage test

  47. CHAPTER QUIZ 8. What battery rating is tested at 32°F (0°C)? • Cold-cranking amperes (CCA) • Cranking amperes (CA) • Reserve capacity • Battery voltage test

  48. CHAPTER QUIZ 9. What gases are released from a battery when it is being charged? • Oxygen • Hydrogen • Nitrogen and oxygen • Hydrogen and oxygen

  49. CHAPTER QUIZ 10. A charge indicator (eye) operates by showing green or red when the battery is charged and dark if the battery is discharged. This charge indicator detects _____. • Battery voltage • Specific gravity • Electrolyte water pH • Internal resistance of the cells

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