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5.2.2, 5.3.1 Batteries, Construction, Function, Diagnosis, and Service
Transcript of 5.2.2, 5.3.1 Batteries, Construction, Function, Diagnosis, and Service
Construction, function, diagnosis, and service
Electrolyte The electrolyte used in automotive batteries is a solution (liquid combination) of 36% sulfuric acid and 64% water. This used for both lead-antimony and lead-calcium (maintenance-free) batteries.
The chemical symbol for this sulfuric acid solution is H2SO4.
H = Symbol for hydrogen
(subscript 2 means there are two atoms of hydrogen)
S = Symbol for sulfur
O = Symbol for oxygen
(subscript 4 indicates four atoms of oxygen)
Electrolyte is sold premixed in the proper proportion and is factory installed. Additional electrolyte must never be added to a battery after the original electrolyte fill.
12. Disconnect the positive jumper cable from the booster battery
13. Disconnect the positive jumper cable from the other battery
Jumping a Battery (cont’d)
1. Make sure the two vehicles are not touching
2. Engage the parking brake and put the transmission in park or neutral
3. Turn off the ignition switch on both vehicles
4. Attach one end of the positive jumper cable to the disabled battery’s positive terminal
Jumping a Battery
Dirt and grease can form a conductive path between the terminals drain the battery
Gassing will deposit sulfuric acid which will corrode the battery terminals, cable clamps, and holddown
Best to remove the battery from the vehicle to clean it
Battery Removal and Cleaning
1. Turn off all accessories
2. Remove the underhood lamp
3. Disconnect the negative battery cable
4. Attach the test light between the negative cable and the negative battery post
5. If the test light glows, there is a current drain
Note: This test only applies to non-computerized vehicles
Battery Drain Test
Using a Test Light
Conductance is a measurement of the battery’s plate surface that is available for chemical reaction
Low-frequency AC signal is sent through the battery
Conductance measurement is calculated with a portion of the returned AC current
A fully charged battery will have a reading between 110~140% of the CCA rating
Battery Conductance Testing
1. Remove the ground cable
2. Connect a battery charger to the battery
3. Connect a voltmeter to the battery
4. Turn the battery charger to 40 amperes
20 to 25 amps for maintenance-free batteries
5. Maintain this rate of charge for 3 minutes
1. Charge the battery
2. Determine the load test specification
50% of the cold cranking amps
Three times the amp-hour rating on the battery
Vehicle manufacturer’s specifications
3. Connect the load leads across the battery
Capacity Test Procedure
Overcharging is very harmful to gel cell batteries as it will dry out the electrolyte
If continually undercharged, a layer of sulfate will build up on the positive plate
Limit the voltage of a charger to 13.8-14.1 volts at 68°C
Gel Cell Batteries
State of charge
Charge Rate Factors
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
Battery Inspection Tips
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
Battery Safety (cont’d)
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
Cracks in the case
Usually indicated by low electrolyte level
Can cause plates to warp or disintegrate
Active material will shed from the plates, causing a shorted cell
Causes of Battery Failure
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 (-17.7°C) without the voltage dropping below 7.2 volts
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
Factors Related to
Battery Current Capacity
Chemical Action During Charge
Chemical Action During Discharge
Fully charged - 1.265 specific gravity
75% charged - 1.225 specific gravity
50% charged - 1.190 specific gravity
25% charged - 1.155 specific gravity
Discharged - 1.120 or lower specific gravity
Battery Specific Gravity Readings
Partitions Cells are separated from other cells by partitions, made of the same material as the outside case of the battery. Electrical connections between cells are provided by lead connectors that loop over the top of the partition and connect the plates of the cells together.
Many batteries connect the cells directly through the partition connectors, which provides the shortest path for the current and the lowest resistance.
Older-style truck and industrial batteries commonly used connectors that extended through the top of the case and over and then down through the case to connect the cells.
Positive versus Negative Plates The positive plates have lead dioxide (peroxide) placed on the grid frame, called pasting. This dark brown active material can react with sulfuric acid of the battery. The negative plates are pasted with pure porous lead, or sponge lead, and are gray in color.
Separators The positive and the negative plates must be installed alternately next to each other without touching. Nonconducting separators are used. These separators are porous and have ribs facing the positive plate.
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
Low-maintenance batteries use a low percentage of antimony (about 2% to 3%) or antimony only in positive plates and calcium for negative plates.
The percentages that make up the alloy of the plate grids constitute the major difference between standard and maintenance-free batteries. Chemical reactions inside each battery are identical regardless of type of grid material used.
Radial-Grid Design Some batteries use a grid design with only vertical and horizontal strips. The battery plate creates electricity from chemical energy, and this current must flow from where it is generated to where it connects to the outside battery post.
The current must move over and up along the grid strips.
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
Be sure to reset the clock and antitheft radio if equipped.
8. Start the jumper vehicle and run at fast idle
9. Attempt to start the disabled vehicle
10. Once the vehicle starts, remove the ground connected to its engine block
11. Disconnect the negative cable from the booster vehicle
Jumping a Battery (cont’d)
5. Connect the other end of the positive jumper cable to the booster battery’s positive terminal
6. Attach one end of the negative jumper cable to the booster battery’s negative terminal
7. Attach the other end of the cable to an engine ground on the disabled vehicle
Jumping a Battery (cont’d)
Make sure the battery is property seated in the tray when replacing it
Do not overtighten the holddown fixture
Install and secure the positive cable, then the negative cable
Be sure to observe polarity
Confirm good connection with a battery terminal test
Battery Removal and
1. Connect a multiplying coil between the negative cable and the negative post
2. Zero the ammeter
3. Connect the inductive pick-up probe around the coil and read the ammeter
4. A reading of less than 0.1 volts is acceptable
Battery Drain Test
Using an Ammeter
6. Check the voltage reading after 3 minutes
If less than 15.5 volts, the battery is not sulfated
If more than 15.5 volts, the battery is sulfated
7. If the battery passes this test, slowly recharge and perform the load test again
Test Procedure (cont’d)
8. Read the voltmeter while applying the load for 15 seconds
9. Check the voltage readings against a chart
10. If the voltage is below specifications, observe voltage level for 10 minutes. If voltage rises to 12.45 volts or higher, replace the battery
If voltage falls below 9.6 volts, battery is
either no good or low on charge.
Capacity Test Procedure (cont’d)
4. Zero the ammeter
5. Connect the inductive pickup around one of the leads
6. Set the tester to the starting position
7. Slowly turn the load control knob to apply the specified load
Capacity Test Procedure (cont’d)
1. Remove all battery vent caps
2. Ensure that electrolyte level is adequate
3. Squeeze the hydrometer bulb and place in a cell
4. Slowly release the bulb, allowing electrolyte to be drawn into the tube
5. The float rises and indicates the specific gravity
State of Charge Test Procedure
Place one lead on the terminal and the other on the clamp
Read the meter while cranking the engine
Should be less than 0.3 volts
Checks the voltage drop between the terminal and clamp
Battery Terminal Test
The only way to restore the battery to a full charge
Minimizes the chances for overcharging
Should only be used to bring the battery charge up enough to crank the engine
Charging the Battery
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 (cont’d)
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
Use the BCI group numbers to verify that the battery is the correct physical size for the vehicle
Always follow the manufacturer’s recommendations
Battery Size Selection (cont’d)
Factors that determine battery size
A general rule is 1 CCA per cubic inch of engine displacement
Battery Size Selection
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
Calculated by multiplying the amp-hour rating by the battery voltage
Battery Ratings (cont’d)
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
Grid growth when exposed to high temperatures
Inability to withstand deep cycling
Low reserve capacity
Faster discharge by parasitic loads
Shorter life expectancy
Maintenance-Free Batteries (cont’d)
Larger reserve of electrolyte
Increased resistance to overcharging
Longer shelf life
Can be shipped with electrolyte installed
Higher cold cranking amps rating
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).
Difference in potential (voltage) between lead peroxide and lead in acid is approximately 2.1 volts.
During Discharging The positive-plate lead dioxide (PbO2) combines with the SO4 from the electrolyte and releases its O2 into the electrolyte, forming H2O. The negative plate also combines with the SO4 from the electrolyte and becomes lead sulfate (PbSO4).
HOW A BATTERY WORKS
Cells Constructed of positive and negative plates, cells have insulating separators between each plate. A cell is also called an element, and is actually a 2-volt battery, regardless of number of positive or negative plates used.
The greater the number of plates used in each cell, the greater the amount of current that can be produced. Typical batteries contain four positive plates and five negative plates per cell.
A 12-volt battery contains six cells connected in series, producing 12 volts (6 2 = 12) and has 54 plates (9 plates per cell 6 cells).
If the same battery had five positive plates and six negative, 11 plates per cell (5 + 6), or 66 plates (11 plates 6 cells), it would have the same voltage, but the amount of current (amps) the
battery could produce would be increased.
Each positive and negative plate in a battery is constructed on a framework or grid of lead. Lead is soft and must be strengthened by adding antimony or calcium for battery use. Grids hold the active material and provide electrical pathways for the current created in the plate.
Maintenance-Free versus Standard Battery Grids A normal battery uses up to 5% antimony in the plate grids to add strength. The more amount of antimony, the more gassing (hydrogen and oxygen gases released), and the more water the battery will use.
Maintenance-free batteries use calcium instead of antimony, because 0.2% calcium has the same strength as 6% antimony.
Conventional Battery Components
Acts as a voltage stabilizer for the entire automotive electrical system
Stores energy for extended periods of time
Battery must be in good condition to test an electrical charging and starting systems
Functions of a Battery (cont’d)
1. Stabilize battery by performing a capacity test and waiting ten minutes
2. Connect a voltmeter across the battery
3. Measure the voltage to 1/10th of a volt
4. A reading of 12.4 volts or more indicates that the battery has over 75% charge
Open Circuit Voltage Test Procedure
1. Set the voltmeter on a low voltage scale
2. Connect the negative lead to the negative terminal
3. Run the positive lead across the top and sides of the battery
4. If voltage is present, the battery should be cleaned with baking soda and water
Leakage Test Procedure
Post or top terminals
Used on most automotive batteries
Are threaded and positioned on the side of the battery
Used by some imports
Types of Battery Terminals
Only pure distilled water should be added to a battery. If distilled water is not available, clean drinking water can be used.
Some water (H2O) escapes during charging as a result of the gassing produced by the chemical reactions.
Battery capacity is determined by the amount of active plate material in the battery and the area of the plate material exposed to the liquid, called electrolyte, in the battery.
A cutaway battery showing the connection of the cells to each other through the partition.
The radial spokes act as a superhighway system for the current to travel from all areas of the grid to the battery post.
A grid with a radial-grid design has lower resistance and can provide more current more rapidly than can the non-radial-grid design used in conventional batteries.
The tester determines the following:
Good battery—the battery can return to service
Charge and retest—fully recharge battery and return to service
Replace the battery—battery not serviceable; should replace
Bad cell—replace—battery not serviceable; should be replaced
GM, Chrysler and Ford specify an electronic conductance tester be used to test batteries in vehicles still under factory warranty. This sends a signal through the battery and the conductance of the cells are determined by the electronics and program in the unit. The unit can determine the CCA, state-of-charge, and voltage of the battery.
ELECTRONIC CONDUCTANCE TESTING
All batteries must be secured to prevent damage and possible shorting
Helps reduce vibration and increases life of battery
May have a heat shield
Important to prevent early battery failure
This sediment chamber, prevents spent material from causing a short circuit between the plates at the bottom of the battery.
Inside the case are six cells (for 12-volt), each with positive and negative plates. Built in the bottom are ribs to support the lead-alloy plates and provide space for sediment to settle.
Most automotive battery cases (container or covers) are constructed of polypropylene, a thin (approx. 0.08 inch [.0 millimeters] thick), strong, and lightweight plastic. Industrial and truck batteries are constructed of a hard, thick, rubber material.