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

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 Lead strap Separators
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. Most automotive batteries have six elements
Battery Element
Most automotive batteries have six elements

18. Case, Cover, and Caps Battery case Battery cover Battery caps
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 holds the elements and electrolyte
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 should just touch the split ring in the top of the case

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

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