MBEYA UNIVERSITY OF SCIENCE AND TECHNOLOGY(MUST) fundamental Of Auto Electric

1. Lead Acid Battery

2. Describe the Construction of a Lead Acid Battery
• Identify various types of batteries
• Identify the components of lead acid battery
• Illustrate the construction of lead acid battery
• Identify common problems and remedies of lead acid battery

3. Introduction
Battery is an electrochemical device for producing and storing
electricity.
There are two types of battery which are:-
 Primary battery
 Secondary battery

4. 1. Primary Batteries
Primary batteries are batteries that cannot be recharged once
depleted. Primary batteries are made of electrochemical cells whose
electrochemical reaction cannot be reversed.
When the battery has delivered all of its voltage to an outside circuit, it
is useless and must be replaced
Example:- Battery used in torch, radio

5. 2. Secondary Batteries
Secondary batteries are batteries with electrochemical cells whose
chemical reactions can be reversed by applying a certain voltage to the
battery in the reversed direction. Also referred to as rechargeable
batteries, secondary cells unlike primary cells can be recharged after
the energy on the battery has been used up

6. Secondary batteries can be further classified into several other types
based on their chemistry.
There are basically four major chemistries for rechargeable batteries;
• Lithium-ion(Li-ion)
• Nickel Cadmium(Ni-Cd)
• Nickel-Metal Hydride(Ni-MH)
• Lead-Acid

7. Lead Acid Battery
Lead acid batteries are usually very large and because of their weight,
they’re always used in non-portable applications such as solar-panel
energy storage, vehicle ignition and lights, backup power and load
levelling in power generation/distribution. The lead-acid is the oldest
type of rechargeable battery and still very relevant and important into
today’s world.

8. Lead Acid battery produces direct current (DC) electricity that flows in
only one direction. When the battery is discharging, it changes
chemical energy into electrical energy, thereby, releasing stored energy.
During charging (current flowing into the battery from the charging
system), electrical energy is converted into chemical energy.
The battery can then store energy until the vehicle requires it.

9. There are four types of automotive batteries currently in use, as
follows:
• Vent-cap (requires maintenance)
• Low-maintenance (requires limited maintenance)
• Maintenance-free (requires no maintenance)
• Recombinant (requires no maintenance)

10. Functions of Automotive Battery
• To operate the starter motor, ignition system, electronic fuel injection
system, and other electrical devices for the engine during engine
starting.
• To supply all of the electrical power for the vehicle when the engine is
not running
• To help the charging system provide electricity when current
demands are above the output limit of the charging system
• Act as a capacitor (voltage stabilizer) that smoothens current flow
through the electrical system.

11. Basic Components of Lead Acid Battery
a. Case/Container
b. Plates
c. Separators
d. Electrolyte
e. Connector
f. Terminals

13. a. Case/Container
The battery case is made of hard rubber or a high- quality plastic. The
case must withstand extreme vibration, temperature change, and the
corrosive action of the electrolyte. The dividers in the case form
individual containers for each element. A container with its element is
one cell.
The battery cover is made of the same material as the container and is
bonded to and seals the container. The cover provides openings for the
two battery posts and a cap for each cell.

14. Battery caps either screw or snap into the openings in the battery
cover. The battery caps (vent plugs) allow gas to escape and prevent
the electrolyte from splashing outside the battery. They also serve as
spark arresters (keep sparks or flames from igniting the gases inside the
battery). The battery is filled through the vent plug openings.
Maintenance-free batteries have a large cover that is not removed
during normal service.

15. b. Plates
There are two types of plates in the battery
• Positive Plates
The positive plates have lead dioxide (peroxides), in paste form placed
onto the grid framework. This process is called pasting. This active
material can react with the sulfuric acid of the battery and is dark
brown in color.
• Negative Plates
The negative plates are pasted to the grid with a pure porous lead,
called sponge lead, and are gray in color.

16. c. Separator
The positive and the negative plates must be installed
alternately next to each other without touching. Non-
conducting separators are used, which allow room for the
reaction of the acid with both plate materials, yet insulate the
plates to prevent shorts. These separators are porous (with
many small holes) and have ribs facing the positive plate.

18. d. Electrolyte
Electrolyte is the term used to describe the acid solution in a battery.
The electrolyte solution in a fully charged battery is a solution of
concentrated sulfuric acid in water. This solution is about 61 percent
water and about 35-39 percent sulfuric acid. The chemical symbol for
this sulfuric acid solution is H 2 SO 4
The electrolyte in the lead-acid storage battery has a specific gravity of
1.265, which means that it is 1.265 times as heavy as water.

19. The amount of sulfuric acid in the electrolyte changes with the amount
of electrical charge also the specific gravity of the electrolyte changes
with the amount of electrical charge. A fully charged battery will have a
specific gravity of 1.265 at 80° F. The figure will go higher with a
temperature decrease and lower with a temperature increase

20. As a storage battery discharges, the sulfuric acid is depleted and the
electrolyte is gradually converted into water. This action provides a
guide in determining the state of discharge of the lead-acid cell. The
electrolyte that is placed in a lead-acid battery has a specific gravity of
1.265. The specific gravity of an electrolyte is actually the measure of
its density. The electrolyte becomes less dense as its temperature rises,
and a low temperature means a high specific gravity. The hydrometer
that used is marked to read specific gravity at 80° F only. Under normal
conditions, the temperature of electrolyte will not vary much from this
mark. However, large changes in temperature require a correction in
your reading.

21. For EVERY 10-degree change in temperature ABOVE 80° F, you must
ADD 0.004 to your specific gravity reading. For EVERY 10-degree
change in temperature BELOW 80° F, you must SUBTRACT 0.004 from
your specific gravity reading. Suppose you have just taken the gravity
reading of a cell. The hydrometer reads 1.280. A thermometer in the
cell indicates an electrolyte temperature of 60° F. That is a normal
difference of 20 degrees from the normal of 80° F. To get the true
gravity reading, you must subtract 0.008 from 1.280. Thus the specific
gravity of the cell is actually 1.272.

22. e. Connector
Electrical connections between cells are provided by lead connector
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 provide the shortest path for the current
and the lowest resistance

24. f. Terminals
Battery terminals are round metal posts extending through the top of
the battery cover. They serve as connections for battery cable ends.
Positive post will be larger than the negative post. It may be marked
with red paint and a positive (+) symbol. Negative post is smaller, may
be marked with black or green paint, and has a negative (-) symbol on
or near it.
Battery terminals provide a means of connecting the battery plates to
the electrical system of the vehicle, also to connect with battery
charger

25. Cells
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; however, many newer batteries
use the same number of positive and negative plates. Each cell is
actually a 2.1 volt battery, regardless of the 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.

26. Typical batteries contain four positive plates and five negative plates
per cell. A 12 volt battery contains six cells connected in series, which
produce 12.6 volts (6x2.1=12.6) and contain 54 plates (9 plates per cell
6 cells). If the same 12 volt battery had five positive plates and six
negative plates, for a total of 11 plates per cell (5 6), or 66 plates (11
plates 6 cells), then it would have the same voltage, but the amount of
current that the battery could produce would be increased.

27. The amperage capacity of a battery is determined by the amount of
active plate material in the battery and the area of the plate material
exposed to the electrolyte in the battery.

28. • Working Principle of Battery
The principle of how a battery works is based on a scientific principle
When two dissimilar metals are placed in an acid, electrons flow
between the metals if a circuit is connected between them.
This can be demonstrated by pushing a steel nail and a piece solid
copper wire into a lemon. Connect a voltmeter to the ends of the
copper wire and nail, and voltage will be displayed.

29. 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). The difference in potential (voltage) between
lead peroxide and lead in acid is approximately 2.1 volts.

30. • During 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. The negative plate also combines with the SO4 from the
electrolyte and becomes lead sulfate (PbSO4 ).
During discharge lead plates become more chemically alike and the
acid becomes weaker hence the voltage will drop

32. • 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
(H 2 O). As the battery is being discharged, the plates and electrolyte
approach the completely discharged state. There is also the danger of
freezing when a battery is discharged, because the electrolyte is mostly
water.

33. • During Charging
During charging, the sulfate from the acid leaves both the positive and
the negative plates and returns to the electrolyte, where it becomes
normal-strength sulfuric acid solution. The positive plate returns to
lead dioxide (PbO 2 ), the negative plate is again pure lead (Pb), and the
electrolyte becomes H 2 SO 4. This chemical differences between plates
leaves the battery ready to deliver power

36. It is normal for some water (H 2 O) in the form of hydrogen and oxygen
gases to escape during charging as a result of the chemical reactions.
The escape of gases from a battery during charging or discharging is
called gassing. Only pure distilled water should be added to a battery. If
distilled water is not available, clean drinking water can be used

37. Wet-charged and Dry-charged Batteries
A wet-charged battery is completely filled with an electrolyte when it is built.
A dry-charged battery is shipped from the factory without electrolyte.
During manufacture, the positive and negative plates are charged and then
completely washed and dried. The battery is then assembled and
sealed to keep out moisture. It will remain charged as long as it is sealed, and
it can be stored for a long time in any reasonable environment.
A dry-charged battery is put into service by adding electrolyte, checking the
battery state of charge, and charging if needed.

38. BATTERY RATINGS
Battery ratings were developed by the Society of Automotive Engineers
(SAE) and the Battery Council International (BCI).
They let the mechanic compare the cranking power of one battery to
another. The two methods of rating lead-acid storage batteries are the
a. Cold cranking amperes rating
b. Reserve capacity rating

39. a. Cold-cranking amperes Rating
The cold-cranking rating determines how much current in amperes the
battery can deliver for 30 seconds at 0° F while maintaining terminal
voltage of 7.2 volts or 1.2 volts per cell. This rating indicates the ability
of the battery to crank a specific engine (based on starter current draw)
at a specified temperature

40. For example, one manufacturer recommends a battery with 305 CCA
for a small four-cylinder engine but a 450 CCA battery for a larger V-8
engine. A more powerful battery is needed to handle the heavier
starter current draw of the larger engine.

41. b. Reserve Capacity Rating
Reserve capacity is the time required (in minutes) for a fully charged
battery at 80˚F under a constant 25-amp draw to reach a voltage of
10.5 volts(1.7 V per cell). This rating helps determine the battery’s
ability to sustain a minimum vehicle electrical load in the event of a
charging system failure. The minimum electrical load under the worst
possible conditions (winter driving at night) would likely require current
for the ignition, low beam headlights, windshield wipers, and the
defroster at low speed

42. Reserve capacity is useful for measuring the battery’s ability to power a vehicle
that has small, long term parasitic electrical loads but enough reserve to crank
the engine. Reserve capacity will appear on the battery as a time interval in
minutes.
For example, if a battery is rated at 90 minutes and the charging system fails,
the operator has approximately 90 minutes (1 1/ 2 hours) of driving time under
minimum electrical load before the battery goes completely dead.

43. COMMON PROBLEMS AND REMEDIES OF LEAD ACID BATTERY
Factors which lead battery Problems
1. Dirty and corroded battery terminals which lead to high resistance
in the electrical circuit.
2. Loose battery terminals cause the melting of the terminals and can
result in sparks, which will lead to an explosion in the battery (very
dangerous!).
3. Vibration. Holding clamps, which are not properly fixed, tightened
results in the active material parting from the grids and the capacity of
the battery get reduced.
4. Over-tightening of hold down clamps. The container will crack or
cause damage to other parts of the vehicle

44. 5. Hammering on battery posts will loosen the terminals or break the
internal components. Always use correct sizes of the spanners when
replacing/removing terminal clamps. Never loosen by force.
6. Dirt and damp on the battery will cause a gradual self discharge.
7. Overcharging causes an excessive loss of water and consequently
causes the plates to shake off their active material (reducing capacity
and service life).
8. Undercharging causes the plates to sulphate (reducing capacity and
service life).
9. Standing in a discharged state will, too, force in the battery plates
sulphation and irreversible damage

45. 10. A faulty regulator or alternator will lead to the contents of the
points 7. and 8
11. A loose fan belt leads to the discharge of the battery. Periodic
attention to the battery as well as to the remainder of the electrical
system, including the fan belt tension, is essential for trouble-free
service in any vehicle.
12. Incorrect electrolyte levels. If these are to low, plates dry out and
sulphate. If these are to high, electrolyte escapes through the air holes,
which can lead to acid damages.
13. Adding acid instead of water increases the density of electrolyte to
the point where it attacks the plates.

46. The following list will assist technicians in troubleshooting batteries.
1. Headlights are dimmer than normal
Discharged battery or poor connections on the battery, engine, or body
2. Solenoid clicks
Discharged battery or poor connections on the battery or an engine
fault, such as coolant on top of the pistons, causing a hydrostatic lock
3. Engine is slow in cranking
Discharged battery, high-resistance battery cables, or defective starter
or solenoid

47. 4. Battery will not accept a charge
Possible loose battery cable connections (If the battery is a maintenance-free
type, attempt to fast charge the battery for several hours. If the battery still will
not accept a charge, replace the battery.)
5. Battery is using water
Check charging system for too high a voltage (If the voltage is normal, the
battery is showing signs of gradual failure. Load test and replace the battery, if
necessary.)
6. Dead every morning
This can be caused by fault ignition switch or there is parasitic problem. Perform
drain test

48. BATTERY MAINTENANCE
If a battery is not properly maintained, its service life will be drastically
reduced. Battery maintenance should be done during every PM cycle.
Complete battery maintenance includes the following:
a. Visually checking the battery.
b. Checking the electrolyte level in cells on batteries with caps. Adding
water if the electrolyte level is low.
c. Cleaning off corrosion around the battery and battery terminals.
d. Checking the condition of the battery by testing the state of charge.

49. a. Visual Inspection Of The Battery
Battery maintenance should always begin with visual inspection. Look
for signs of corrosion on or around the battery, signs of leakage, a
cracked case or top, missing caps, and loose or missing hold-down
clamps.

50. b. Checking Electrolyte Level And Adding Water.-
On vent cap batteries, the electrolyte level can be checked by removing
the caps. Some batteries have a fill ring which indicates the electrolyte
level. The electrolyte should be even with the fill ring. If there is no fill
ring, the electrolyte should be high enough to cover the tops of the
plates. Some batteries have an electrolyte-level indicator (Delco Eye).
This gives a color code visual indication of the electrolyte level, with
black indicating that the level is okay and white meaning a low level.

51. If the electrolyte level in the battery is low, fill the cells to the correct
level with Distilled Water (purified water). Distilled water should be
used because it does not contain the impurities found in tap water. Tap
water contains many chemicals that reduce battery life. The chemicals
contaminate the electrolyte and collect in the bottom of the battery
case. If enough contaminates collect in the bottom of the case, the cell
plates Short Out, ruining the battery.

52. If water must be added at frequent intervals, the charging system may
be overcharging the battery. A faulty charging system can force
excessive current into the battery. Battery gassing can then remove
water from the battery. Maintenance-free batteries do NOT need
periodic electrolyte service under normal conditions. It is designed to
operate for long periods without loss of electrolyte.

53. c. Cleaning The Battery And Terminals
If the top of the battery is dirty, using a stiff bristle brush, wash it down
with a mixture of baking soda and water. This action will neutralize and
remove the acid-dirt mixture. Be careful not to allow cleaning solution
to enter the battery. To clean the terminals, remove the cables and
inspect the terminal posts to see if they are deformed or broken. Clean
the terminal posts and the inside surfaces of the cable clamps with a
cleaning tool before replacing them on the terminal posts.

54. Caution: Do not use a scraper or knife to clean battery terminals. This
action removes too much metal and can ruin the terminal connection.
When reinstalling the cables, coat the terminals with petroleum or
white grease. This will keep acid fumes off the connections and keep
them from corroding again. Tighten the terminals just enough to secure
the connection. Overtightening will strip the cable bolt threads

55. d. Checking Battery Condition.-
When measuring battery charge, you check the condition of the
electrolyte and the battery plates. As a battery becomes discharged, its
electrolyte has a larger percentage of water. Thus the electrolyte of a
discharged battery will have a lower specific gravity number than a fully
charged battery. This rise and drop in specific gravity can be used to
check the charge in a battery. There are several ways to check the state
of charge of a battery.

56. Non-maintenance-free batteries can have the state of charge checked
with a hydrometer. The hydrometer tests specific gravity of the
electrolyte. It is fast and simple to use.
A fully charged battery should have a hydrometer reading of 1.265 . If
below 1.265, the battery needs to be recharged. or it may be defective.

57. Maintenance-free battery uses lead-calcium or strontium alloy instead
of lead antimony plate grid construction because 0.2% calcium has the
same strength as 6% antimony . lead-calcium batteries do not release
as much gas and heat as the older-style(lead antimony), so there is less
consumption of water during normal service and corrosion
Since heat and gassing are the principal reasons for battery water loss,
these changes reduce or eliminate the need to periodically add water.
Reduced water loss also minimizes terminal corrosion, since the major
cause of this corrosion is condensation from normal battery gassing

58. A discharged battery could be caused by the following:
• Defective battery
• Charging system problems
• Starting system problems
• Poor cable connections
• Engine performance problems requiring excessive cranking time
• Electrical problems drawing current out of the battery with the
ignition OFF

59. On maintenance-free batteries a charge indicator eye shows the
battery charge. The charge indicator changes color with levels of
battery charge. For example, the indicator may be green with the
battery fully charged. It may turn black when discharged or yellow
when the battery needs to be replaced. If there is no charge indicator
eye or when in doubt of its reliability, a voltmeter and ammeter or a
load tester can also be used to determine battery condition quickly.

60. BATTERY TESTS
There are several test batteries for proper operation and condition.
These tests are as follows:
• Battery leakage test
• Battery terminal test
• Battery voltage test
• Cell voltage test
• Battery drain test
• Quick charge test

61. • Battery Leakage Test
A battery leakage test will determine if current is discharging across
the top of the battery. A dirty battery can discharge when not in use.
This condition shortens battery life and causes starting problems. To
perform a battery leakage test, set a voltmeter on a low setting. Touch
the probes on the battery, as shown in figure below. If any current is
registered on the voltmeter, the top of the battery needs to be cleaned.

63. • Battery Terminal Test
The battery terminal test quickly checks for poor electrical connection
between the terminals and the battery cables. A voltmeter is used to
measure voltage drop across terminals and cables.
To perform a battery terminal test, connect the negative voltmeter lead
to the battery cable end. Touch the positive lead to the battery
terminal. With the ignition or injection system disabled so that the
engine will not start, crank the engine while watching the voltmeter
reading.

64. If the voltmeter reading is 0.5 volts or above, there is high resistance at
the battery cable connection. This indicates that the battery
connections need to be cleaned. A good, clean battery will have less
than a 0.5 volt drop.

66. • Battery Voltage Test
The battery voltage test is done by measuring total battery voltage with an
accurate voltmeter or a special battery tester. This test determines the
general state of charge and battery condition quickly.
The battery voltage test is used on maintenance-free batteries because these
batteries do not have caps that can be removed for testing with a
hydrometer. To perform this test, connect the voltmeter or battery tester
across the battery terminals. Turn on the vehicle headlights or heater blower
to provide a light load. Now read the meter or tester. A well-charged battery
should have over 12 volts. If the meter reads approximately 11.5 volts, the
battery is not charged adequately, or it may be defective.

68. • Cell Voltage Test
The cell voltage test will let you know if the battery is discharged or
defective. Like a hydrometer cell test, if the voltage reading on one or
more cells is 0.2 volts or more lower than the other cells, the battery
must be replaced.
To perform a cell voltage test, use a low voltage reading voltmeter with
special cadmium (acid resistant metal) tips. Insert the tips into each
cell, starting at one end of the battery and work your way to the other.
Test each cell carefully. If the cells are low, but equal, recharging usually
will restore the battery. If cell voltage readings vary more than 0.2 volts,
the battery is BAD.

70. • Battery Drain Test
A battery drain test checks for abnormal current draw with the ignition
off. If a battery goes dead without being used, you need to check for a
current drain.
To perform a battery drain test, set up an ammeter, as shown in figure
below. Pull the fuse if the vehicle has a dash clock. Close all doors and
trunk (if applicable). Then read the ammeter. If everything is off, there
should be a zero reading. Any reading indicates a problem. To help
pinpoint the problem, pull fuses one at a time until there is a zero
reading on the ammeter. This action isolates the circuit that has the
problem.

72. • Quick Charge Test
The quick charge test, also known as 3-minute charge test, determines
if the battery is sulfated. Charge the battery for 3 minutes at 30 to 40
amps. Test the voltage while charging. If the voltage goes ABOVE 15.5
volts, the battery plates are sulfated and the battery needs to be
replaced.

73. BATTERY CHARGING
When testing shows that a battery requires charging, a battery charger is
required to reenergize it. The battery charger will restore the charge on the
plates by forcing current back into the battery. The battery charger uses AC
(Alternating Current) current from a wall outlet, usually 120 volts, and steps
it down to a voltage slightly above that of a battery, usually 14-15 volts.
There are basically two types of battery chargers
a. Slow charger
b. Fast (quick) charger.

74. a. Slow Charger
The slow charger is also known as the trickle charger. It feeds a small
amount current back into the battery over a long period of time. When
using a trickle charger, it takes about 12 hours at 10 amps to fully
charge a dead battery. However, the chemical action inside the battery
is improved. During a slow charge, the active materials are put back
onto the battery plates stronger than they are during a fast charge. It is
always better for the battery to use a trickle charger when time allows.

75. b. Fast Charger
The fast charger, or quick charger and sometimes called the boost
charger, forces a high amount of current flow back into the battery. A
fast charger is commonly used in shops to start an engine or get the
vehicle out of the shop quickly because there is no time to wait for a
slow charger.
Fast charging is beneficial if you just need to start the engine; if time
allows, use the slow charge.

76. When using a fast charger, do not exceed a charge rate in excess of 35
amps. Also, ensure the battery temperature does not exceed 125 F.
Exceeding either one could cause damage to the battery. If there is a
possibility that the battery is frozen, do not charge the battery.
Charging a frozen circuit can rupture the battery case and cause an
explosion. Always allow the battery time to thaw before charging it.

77. Placing New Batteries In Service
When you are mixing electrolyte, NEVER POUR WATER INTO THE ACID.
ALWAYS POUR ACID INTO WATER. If water is added to concentrated
sulfuric acid, the mixture may explode and cause severe burns. Pour
the acid the water slowly, stirring gently but thoroughly all the time.
Large quantities of acid may require hours of safe dilution.
When placing battery in the vehicle start with +VE Terminal of the
battery followed by –VE terminal of the battery
When you remove the terminal of the battery start with –VE Terminal
of the battery followed by +VE Terminal of the battery

78. Group Assignment
1.There are four types of automotive batteries currently in use, which are
• Vent-cap (requires maintenance)
• Low-maintenance (requires limited maintenance)
• Maintenance-free (requires no maintenance)
• Recombinant (requires no maintenance)
Explain the mechanism of the three last types
2. Why when disconnecting battery you should start with Negative terminal
followed by positive while when connecting a battery should start with positive
terminal followed by negative terminal?