Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

1. PublisherThe Goodheart-Willcox Co., Inc.Tinley Park, Illinois PowerPoint for Modern Automotive Technology by Russell Krick

2. Chapter 28 Automotive Batteries

3. Contents • Battery principles • Battery functions • Battery construction • Wet- and dry-charged batteries • Maintenance-free battery • Battery ratings • Battery temperature and efficiency

4. Battery Principles • An automotive battery is an electrochemical device • It produces and stores direct current electricity

5. Battery Parts

6. Discharging • Changes chemical energy into electrical energy • Stored energy is released

7. Charging • Electrical energy is converted to chemical energy • Energy is stored until needed

8. Battery Cycling • Repeated charging and discharging • Deep cycling • going from a very low charge to full charge • can shorten service life

9. Basic Battery Cell • Contents: • negative plate • positive plate • container • electrolyte (battery acid) • When a load is connected to the cell, current will flow through the load

10. Lead-Acid Battery Cell Electrolyte causes a chemical reaction between the plates, producing 2.1 volts

11. Cell Action(Charging) • Alternator causes free electrons to be deposited on the negative (–) plate • This causes the plates to have a difference in potential (electrical pressure or voltage)

12. Cell Action(Discharging) • Load is connected across the terminals • Current flows through the load to equalize the difference in charges on the plates • Excess electrons (current) move from the negative plate through the load to the positive plate

13. Battery Cycling

14. Battery Functions • Operate the starting motor, ignition system, fuel injection, and other electrical devices during cranking • Supply electrical power when the engine is not running • Supply electrical power when current demands exceed alternator output • Act as a capacitor (voltage stabilizer) • Store energy for extended periods

15. Battery Construction • Batteries must be built to withstand harsh conditions: • severe vibration • extreme temperatures • corrosive chemicals • high current discharge • prolonged periods without use

16. Battery Element • Battery plates • grid coated with porous lead • several in each cell • Lead strap • one connects several negative plates • another connects several positive plates • Separators • insulating material between plates that keep them from touching each other

17. Battery Element Most automotive batteries havesix elements

18. Case, Cover, and Caps • Battery case • high-quality plastic • holds the elements and electrolyte • Battery cover • bonded to the top of the case • seals the top • Battery caps • keep electrolyte from splashing out • serve as spark arrestors

19. Case, Cover, and Caps Case holds the elements and electrolyte

20. Electrolyte • Mixture of sulfuric acid and distilled water • Poured into each cell until plates are covered • Also known as battery acid • Warning: electrolyte causes serious burns or blindness if it comes in contact with your skin or eyes!

21. Electrolyte Electrolyte should just touch the split ring in the top of the case

22. Charge Indicator Changes color to show the general state of charge of the battery

23. Battery Terminals Means of connecting the battery to the vehicle’s electrical system

24. Battery Voltage • Open circuit cell voltage is 2.1 volts • Cells are connected in series • Battery voltage depends on the number of cells • A 12-volt battery has 6 cells and an open circuit voltage of 12.6 volts • A 6-volt battery has 3 cells and an open circuit voltage 6.3 volts

25. Battery Voltage

26. Two-Battery Systems • Parallel • connected negative to negative • connected positive to positive • two 12-volt batteries produce 12 volts, high current • Series • connected positive to negative • two 12-volt batteries produce 24 volts

27. Battery Cables A. Post-type B. Side terminal C. Braided ground D. 90º post-type E. Solenoid-to-starter

28. Cable Connections The negative cable grounds on the engine block and the positive cable connects to the starter solenoid

29. Battery Tray and Retainer Holds battery securely in place. May house a battery temperature sensor.

30. Battery Tray and Heat Shield Protects battery from excess engine heat by routing air between heat shield and battery case

31. Wet- and Dry-Charged Batteries • No difference in the materials used in each • Only difference is in how they are prepared for service

32. Wet- and Dry-Charged Batteries • Wet-Charged Battery • filled with electrolyte and charged at the factory • very common in many locations • Dry-Charged Battery • contains fully charged elements • does not contain electrolyte • leaves the factory in a dry state • has a long shelf life

33. Maintenance-Free Battery • Does not use removable filler caps • Calcium is used to make the plates, which reduces gassing • Reduced water loss decreases service requirements • Less gassing results in less chemical loss, which results in increased battery life

34. Gel Battery • Works like a lead-acid battery • Contains a pastelike electrolyte • The electrolyte will not leak out if the case is cracked or broken, and the battery will continue to function

35. Gel Battery • A complete seal eliminates gassing and reduces the risk of explosion • Improper charging can burn a void in the electrolyte gel • Burning can permanently lower power output • A specific charging rate is required, which is not required with a lead-acid battery

36. Absorbed Glass Mat Battery • Also known as an AGM battery • Contains a fiber matting that absorbs the liquid electrolyte • Battery has only enough electrolyte to wet the matting

37. Absorbed Glass Mat Battery • Vibration and impact resistant and will not leak, even if the case is damaged • Sealing does not allow gassing, reducing the risk of explosion • Not as sensitive to improper charging as gel batteries

38. Battery Ratings • Cold cranking rating • Reserve capacity rating • Amp-hour rating

39. Cold Cranking Rating • Determines the current a battery can deliver for 30 seconds at 0ºF (-18ºC) while maintaining terminal voltage of 7.2 volts (1.2 volts per cell) • Expressed as cold cranking amps (CCA) • Indicates ability to crank the engine at cold temperatures • Typical applications: • 305 CCA for small 4-cylinder engine • 450 CCA for 8-cylinder engine

40. Reserve Capacity Rating • Time needed to lower battery terminal voltage below 10.2 volts (1.7 volts per cell) at a discharge rate of 25 amperes at 80ºF (27ºC) • Expressed in minutes • example: If a battery is rated at 90 minutes and the charging system fails, the driver has approximately 90 minutes of driving time with a current use of 25 amperes before the battery goes completely dead

41. Amp-Hour Rating • Once used to indicate battery power • Measures the current that the battery could produce for 20 hours at 80ºF (27ºC) with the battery voltage above 10.5 volts

42. Battery Temperature and Efficiency • As battery temperature drops, output is reduced • chemical process is slowed • battery cannot produce as much current

43. Temperature versus Efficiency

44. Parasitic Loads • Current draw present when engine and ignition are shut off • Computers and clock require constant power • Over prolonged periods, these may discharge the battery enough to prevent starting