CHAPTER ELEVEN
Automotive Batteries, and Battery Testing
Functions of a Battery
•	Operates the electrical devices for the engine during cranking and starting
•	Supplies electrical power for the vehicle accessories when the engine is not running
•	Furnishes current for a limited time whenever electrical demands exceed charging system output
Functions of a Battery (continued)
•	Acts as a voltage stabilizer for the entire automotive electrical system
–	Absorbs voltage spikes
•	Stores energy for extended periods of time
–	Lets you start the car days later
Parts of a Battery
•	Case (2 mm thick)
•	Sediment Chamber
•	Grid / Designs
•	Maintenance Free
VS Standard Grid Desgn

Electrolyte
•	“Acid”
•	36% Sulfuric Acid
•	64% Pure Distilled Water
•	H2SO4
•	How it works..
•	Dead battery = pure water
•	Charge = H into the air
•	“Battery On Floors?”
“The eye”
•	Green = ok
•	Red = charge
•	USED ONLY BY THE PARTS PERSON!
•	Cannot be used by the tech for proper testing!

•	State of Charge	SG.		Voltage		
•	100%		1.265	12.6-8v
•	75%			1.225	12.4v
•	50%			1.19	12.2v
•	25%			1.155	12v
•	Discharged		1.120	11.9v

Causes of Battery Failure
•	Cracks in the case
•	Overcharging – 15.5 volts
–	Usually indicated by low electrolyte level
–	Can cause plates to warp or disintegrate
•	Vibration
–	Active material will shed from the plates, causing a shorted cell
Hold downs
•	Increase battery life
•	Prevent cell damage
•	Prevent fires and acid loss
•	Required by state inspection
•	No newspapers, bungee or blocks of wood – please… are you a professional?
Factors Related to Battery Current Capacity
•	The size of the cell plates
•	The weight of the positive and negative plate active material
•	The weight of the sulfuric acid in the electrolyte solution
•	More plates
•	Battery design and type
Battery Ratings
•	Cranking Amperes
–	CA – Number of Amps a battery can supply at 32 Deg F
•	Ampere-hour rating
–	The amount of steady current that a fully charged battery can supply for 20 hours at 80° F (26.7° C)
•	Cold cranking amps (CCA) rating
–	The load in amperes that a battery can deliver for 30 seconds at 0°F (-18° C) without the voltage dropping below 7.2 volts 
•	(most common and important in battery selection!)
Battery Ratings (continued)
•	Reserve capacity rating
–	The length of time in minutes that a fully charged battery can be discharged at 25 amperes before the battery voltage drops below 10.5 volts
Battery Types
•	Deep Cycle (Marine Battery)
–	Can withstand major charge and discharge cycles.
–	Uses thicker plate grids
–	Larger in size and weight

•	Hybrid Batteries
–	Uses two metals (calcium alloy)
–	Lower water usage

Maintenance -Free Batteries
•	Advantages
–	Larger reserve of electrolyte
–	Increased resistance to overcharging
–	Longer shelf life
–	Can be shipped with electrolyte installed
–	Higher cold cranking amps rating
Maintenance -Free Batteries
•	Disadvantages
–	Grid growth when exposed to high temperatures
–	Inability to withstand deep cycling
–	Low reserve capacity
–	Faster discharge by parasitic loads
–	Shorter life expectancy
AGM/Recombination Batteries
•	Uses gel instead of liquid electrolyte
•	Can be installed in any position
•	Is corrosion free and has very low maintenance
•	Can last up to four times longer than conventional batteries
•	Can withstand deep cycling without damage
•	Can be rated at over 800 cold cranking amperes
  AGM (Absorbent Gas Mat)

•	Costs up to three times as much as a conventional maintenance free unit
•	Also know as “Dry cell”
Selecting the Correct Battery
•	Factors that determine battery size
–	Engine size
–	Climactic conditions
–	Vehicle options
•	A general rule is 1 CCA per cubic inch of engine displacement
Selecting the Correct Battery (continued)
•	Use the BCI group numbers to verify that the battery is the correct physical size for the vehicle
•	Always follow the manufacturer’s recommendations
•	http://www.batterycouncil.org/
Battery Safety
•	Do not allow battery acid to come in contact with skin, eyes, or clothing
•	Observe polarity when making connections to the battery
•	Always disconnect the negative cable first
•	Always connect the negative cable last
Battery Safety (continued)
•	Avoid any arcing or open flames near a battery
•	Follow manufacturer’s recommendations when charging
•	Add only distilled water when low
•	Do not wear jewelry when servicing a battery
Battery Safety (continued)
•	Never lay tools on a battery
•	Always wear safety glasses when servicing a battery
•	If frozen, allow the electrolyte to defrost before doing any service
Types of Battery Terminals
•	Post or top terminals
–	Used on most automotive batteries
•	Side terminals
–	Are threaded and positioned on the side of the battery
•	L-terminals
–	Used by some imports

Battery Cables
•	They are normally 4 or 6 gauge wires
•	The positive cable is usually red and the negative cable is usually black
•	The negative cable is attached to the engine block
•	The negative cable may be made with no insulation

Battery Inspection Tips
•	Check the date code
•	Check the case for damage, dirt, and corrosion
•	Check the electrolyte level, color, and odor
•	Check the condition of the cables
•	Check for signs of obvious neglect
•	Check the battery hold-down fixture