Chapter 3: BATTERIES – VEHICLE BATTERIES

Introduction

The battery is an electrochemical device. It converts chemical

energy into electrical energy.

The battery produces electricity to operate the starting motor and

ignition system while starting the engine.

Discharging - Battery changes chemical energy into electrical

energy - Current flow out of the battery

Charging - Electrical energy is converted into chemical energy -

Battery stores the energy until it needed

Automotive Batteries An automotive battery is a type of

rechargeable battery that supplies electric energy to an automobile.

Automotive batteries (usually of lead-acid type) provide a nominal 12-volt potential difference by connecting six galvanic cells in series.

Each cell provides 2.1 volts for a total of 12.6 volt at full charge.

Lead-acid batteries are made up of plates of lead and separate plates of lead dioxide, which are submerged into an electrolyte solution of about 35% sulfuric acid and 65% water.

The function of Battery

1. To operate starter motor, ignition system, relays during

cranking of the engine

2. Supply all of the electrical power for the car whenever the

engine is not running

3. Help the charging system in providing electricity when

demand is above the output of the charging system

4. Store electrical energy for extended periods

5. Act as a voltage stabilizer that smoothen the current

through the vehicle electrical system

6. To allow dynamic memory and alarm system to remain

active when the vehicle is left for a period of time

Only the battery as power supply.

When engine is stopped, the battery operates all electrical devices .

When engine is starting, the battery operates the starter motor discharged current flows from the battery

When only the alternator is the power supply

After the engine starts, the alternator operates all electrical devices & recharges the battery at the same time - charging current flows into the battery

When both are used as a power supply

Right after the engine is started, if the electrical load is too great for the alternator, the battery contributes electrical power - discharged current flows from the battery

While the car is running, almost all power is supplied by the alternator.

An imbalance in the relationship between the battery and the alternator may cause the battery to become discharge.

Construction of the Battery An automobile battery contains; 1. diluted sulphuric acid (electrolyte) 2. positive plates 3. negative plates

Construction of the Battery Internally, a battery is separated into several cells (usually six in

the case of automobile batteries) and in each cell there are several battery elements (plates), all submerged in the electrolyte

The positive plates and negatives plates are each connected together by separate plate straps

These groups of positive and negative plates are then placed alternately, separated by separators and fibre glass mats .

Grouping the plates in this way serves to enlarge the contact area between the active materials and the electrolyte, allowing a greater amount of electricity to be supplied.

Construction of the Battery

Construction of the Battery

.

1. Positive Plates Lead peroxide (brown colour) as active material formed on mesh / grid framework Strap together to form positive plate group Standard car battery has 1.52 mm grid thickness - One plate less is

common practice

2. Negative Plates Pure lead (grey colour) sponge lead as active material formed on

mesh / grid framework Strap together to form negative plate group Standard car battery has 1.40 mm grid thickness -One plate more is

common practice

3.Separator Insulated and corrosion resistant material such as PVC, paper

based, glass fiber Must have correct pore structure for the electrolyte passage - Prevent

positive & negative plate from touching.

Construction of the Battery

Construction of the Battery4.Grid To conduct electricity to and from active material and to

support the active material Grid is made of lead + antimony - but promotes electrolyte

gassing (loss of electrolyte) Grid of lead + calcium is used for maintenance free battery

minimum loss of electrolyte

Heavy duty

Construction of the Battery5.Container / battery case Plastic container, corrosion resistance material It is divided into six compartments or cells Upper and lower electrolyte level markers are provided on

the translucent battery case showing electrolyte level The plates are raised up off the bottom of the case with ribs

to prevent them from shorting out if any of the active materials should happen to fall from the plates

Construction of the Battery6. Vent Plugs Vent plugs are caps for the holes that are used for adding electrolyte They are also designed to separate the hydrogen gas (from when

the battery charges) and sulphuric acid mist that are present in the air inside the battery by allowing the hydrogen gas to escape through the vent holes and the sulphuric acid mist to condense on the sides of the vents and drop back into the battery

Construction of the Battery7. CELL CONNECTORS: Heavy, cast alloy metal straps are welded to the negative terminal of one cell and the positive terminal of the adjoining cell until all six cells are connected in series.

8. CELL PARTITIONS: Part of the case, the partitions separate each cell.

9. TERMINAL POSTS: Positive and negative posts (terminals) on the case top have thick, heavy cables connected to them. These cables connect the battery to the vehicle's electrical system (positive) and to ground (negative).

10. ELECTROLYTE: A mixture of sulfuric acid (H2SO4) and water (H2O). It reacts chemically with the active materials in the plates to create an electrical pressure (voltage). And, it conducts the electrical current produced by that pressure from plate to plate. A fully charged battery will have about 36% acid and 64% water.

S.G (Specific Gravity)

•Electrolyte - Sulfuric acid & distilled water(H2O)

• Electrolyte that are used in batteries today have a specific gravity (S.G) of either 1.26 or 1.28 (at 20°C) when the battery is fully charged .

• The difference is due to the particular ratio of distilled water to sulphuric acid - the electrolyte having a S.G of 1.26 contains 65% distilled water and 35% sulphuric acid while the electrolyte having a S.G of 1.28 contains 63% distilled water and 37% sulphuric acid

Battery Identification Codes Batteries that are made in Japan are given a battery

identification code according to a Japan Industrial Standard (JIS)

The code indicates the battery capacity, dimensions and the position of the positive terminal (right or left side)

Battery Identification Codes 1.Performance This indicates the battery's capacity indirectly. The chart shows the

relationship between battery identification codes and battery capacity. The capacity is expressed in ampere-hours

Battery 10 code

I Battery capacity

Battery 10 code

Battery capacity

IS-hour rate) IS-hour rate)

288 17 R/L 24 65 D 26 R/L 52

34817R/L 27 75 D 26 R/L 52

288 19 R/L 24 80 D 26 R/L 55

348 19 R/L 27 65 D 31 R/L 56

36820 R/L 28 75 D 31 R/L 60

38820 R/L 28 95D31R/L 64

46824R/L 36 95E41 R/L 80

50824 R/L 36 105E41 R/L 83

55824 R/L 36 115E41 R/L 88

32 C 24 R/L 32 130E41 R/L 92

50D20R/L 40 115F51 96

55 D 23 R/L 48 150 F 51 108

65 D 23 R/L 52 145 F 51 112 .

48 D 26 R/L 40 170 F 51 120

55 D 26 R/L 48

Battery Identification Codes 2) Battery Width and Height The battery's width and height combination is indicated by

one of the eight letters (A to H)

Width (mm) Height (rnrn)

A 162 127

B 203 127 or 129

C 207 135

0 204 173

E 213 176

F 213 182

G 213 222

H 220 278

Battery Identification Codes 3.Position of the Positive Terminal The position of the positive terminal of a battery is indicated

either by R (right side), L (left side) or blank

Battery Identification Codes

CELL THEORY A lead-acid cell works by a simple principle: when two different metals are

immersed in an acid solution, a chemical reaction creates an electrical pressure.

Lead dioxide (Pb02) has a positive electrical charge. The other metal is sponge lead (Pb). It has a negative electrical charge. The electrolyte, acid solution is a mixture of sulfuric acid (H2SO4) and water (H20).

If a conductor and a load are connected between the two metals, current will flow. This discharging will continue until the metals become alike and the acid is used up. The action can be reversed by sending current into the cell in the opposite direction. This charging will continue until the cell materials are restored to their original condition.

Battery Electromotive Force (EMF) The electromotive force (EMF) generated by one cell is

approximately 2.1 V, regardless of the quantity or size of the plates

Since automobile batteries have six cells that are connected in series, their nominal output EMF is about 12 V

ELECTROCHEMICAL REACTION A lead-acid storage battery can be partially discharged and

recharged many times. There are four stages in this discharging/charging cycle.

  1. CHARGED: A fully charged battery contains a negative

plate of sponge lead (Pb), a positive plate of lead dioxide (Pb02), and electrolyte of sulfuric acid

(H2SO4) and water (H20).

ELECTROCHEMICAL REACTION2. DISCHARGING : As the battery is discharging, the electrolyte becomes

diluted and the plates become sulfated The electrolyte divides into hydrogen (H+) and sulfate(S04

2-) The ion hydrogen (H+) combines with oxygen (02-) from the positive plate to

form more water (H20). The sulfate combines with the lead (Pb) in both plates to form lead sulfate

(PbS04)

At Positive Plate: Pb02+ S04

2- + 4H+ + 2e- PbS04 + 2H20 At Negative Plate: Pb + S04

2- PbS04 + 2e-

Net reaction equationPb02 + 2H2S04 + Pb 2PbS04 + 2H20

Chemical reaction equation (Discharging)

ELECTROCHEMICAL REACTION3. DISCHARGED: In a fully discharged battery, both plates

are covered with lead sulfate (PbSO4) and the electrolyte is diluted to mostly water (H2O).

ELECTROCHEMICAL REACTION 4. CHARGING: During charging, the chemical action is reversed. Sulfate

(S042-) leaves the plates and combines with hydrogen (H+) to become

sulfuric acid (H2SO4). Free oxygen (0) combines with lead (Pb) on the positive plate to form lead

dioxide (Pb02). Gassing occurs as the battery nears full charge, and hydrogen bubbles out

at the negative plates, oxygen at the positive.

At Positive Plate: PbS04 + 2H20 Pb02 + S04

2- + 4H+ + 2e- At Negative Plate: PbS04 + 2e- Pb + S04

2- Net reaction equation2PbS04 + 2H20 Pb02 + 2H2S04 + Pb

Chemical reaction equation (Charging)

Battery Capacity Rating

Battery capacity is the amount of electrical energy the battery can deliver when fully charged.

All six cell storage batteries have the same voltage but they may have a different capacity.

Capacity is a measure of how much current it can produced and how long it can sustain this current.

4 methods of defining battery capacity:

1.Reserve capacity rating Defined as the time in minutes for the fully charged battery

voltage to fall to 10.5 V with a constant load of 25 A at 80˚F (26.7'C) - how long the battery can sustain a 25 A discharge.

Batteries used on various Toyota vehicles have RC ratings ranging from 55 to 115 minutes.

Battery Capacity Rating 2.Cold Cranking Amperes (CCA) The current that the battery will give at 0˚F (-17.8˚C) for a

specified interval of time while maintaining a voltage of at least to an end voltage - three standard - BS (British Standard), DIN (German Standard) and SAE (Society of Automotive Engineers

Standard Duration End Voltaqe

BS 60 seconds 8.4 volts

DIN 30 seconds 9.0 volts

SAE 30 seconds 7.2 volts

Battery size CCA

Standard JIS model

NS40ZAL 36B20 275

NS60 46B24 325

NS70 65026 420

N70 65031 445

55023 55023 355

DIN 360

Table 1 :Standard applied

Table 2 : CCA battery rating

Battery Capacity Rating 3. AMP-HOURS (AH)

• Amp-Hour Rating specifies, the current the battery can provide for 20 hours at 80˚F (26.7˚C) while maintaining a voltage of at least 1.75 volts per cell (10.5 volts total for a 12- volt battery).

• For example, a battery that can deliver 4 amps for 20 hours is rated at 80 amp-hours (4 x 20 =80). Example: A 50Ah battery can expect to deliver 2.5 Ampere for 20 hours •Batteries used on various vehicles have AH ratings ranging from 40 to 80 amp-hours.

4. POWER (WATTS) The battery's available cranking power may also be measured in watts. The Power Rating, in watts, is determined by multiplying the current available by the battery voltage at 0˚F (-1 7.8˚C). •Batteries used on various vehicles have power ratings ranging from 2000 to 4000 watts.•P=IV where ( P=power, I=current, V=voltage )

Internal Resistance All batteries have internal resistance but it is very

low. Eg; 0.005 ohm for a good condition battery and may be 0.05 ohm for a fair condition battery.

The internal resistance of the battery causes the battery's output voltage to decrease

As battery age, internal resistance increase V = E-Ir

V is actual terminal voltage, E theoretical voltage, r is internal resistance

Batteries Self-discharge

Over a period of time, a battery which is not used will gradually lose its charge due to several factors;

1. Internal chemical reaction due to antimony deposits on negative plate.

2. Leakage currents due to dirt and fume to form conducting path

3. Sediment at the bottom of the battery

Self discharge at the rate of 0.2% to 1 % of the battery Ah per day, depending on the age of the battery and

temperature.

To avoid high temperature discharge, Store in cool place Charge battery every month if not use Once fully discharge it may not fully recover even after

recharge

Sulphation Under normal discharging, fine crystals of lead sulphate are

formed on the plates and by charging, these are convertible

If battery is left discharge for long period, the crystal turns

into coarse lead sulphate which are not easily convertible

Sulphation causes the reduction in battery Ah and also slowdown the charging process causing the battery to become very hot

In minor sulphation cases, extended period of charging at low current will improve but in serious cases the battery is condemned due to internal short

Battery Maintenances &

Services

Safety precautions :• Wear gloves and safety glasses. • Remove rings, watches, other jewelry. • Never use spark-producing tools near a battery. • Never lay tools on the battery. • When removing cables, always remove the ground cable first. • When connecting cables, always connect the ground cable last. • Do not use the battery ground terminal when checking for ignition

spark. • Be careful not to get electrolyte in your eyes or on your skin, the car

finish, or your clothing. • If you have to mix battery electrolyte, pour the acid into the water -

not the water into the acid. • Always follow the recommended procedures for battery testing and

charging and for jump starting an engine.

Battery Maintenance

Battery Maintenance includes: 1. Making visual inspection of the battery 2. Cleaning the battery top, terminal and

cable clamp 3. Testing the battery 4. Charging the battery

Battery Visual Inspection

Look for: 1. Electrolyte leakage 2. Electrolyte level 3. Crack in the case (may result from

overtightening the hold-down clams) or top (may result from using wrong wrench)

4. Loose or missing hold-down clamps 5. Loose terminals (may result from

overtightening the cable bolts)

Cleaning the Battery Corrosion around the terminals and clamps can be cleaned

by using a battery-terminal brush (with a solution of baking soda and water)

Battery Trouble Diagnosis The two main causes of battery troubles are overcharging and

undercharging 1. Overcharging Causes damage to the plate and shortens battery life. The high voltage can also damage other electrical and electronic

components For a vent-cap battery - shown by frequent addition of water For a maintenance-free battery - shown by low electrolyte level Other signs of overcharging:1. Voltage> 15 volt 2. Electrolyte dry too fast 3. Vigorous bubbles 4. Pungent smell 5. Surface always wet 6. Bulb always burnt 7. Battery bulge

Battery troubles diagnosis

2.Undercharging Possible causes include: 1. Charging system malfunction 2. Defective connections in charging system3. Excessive load demands on battery 4. Defective battery 5. Self-discharge resulting from battery

sitting idle for long periods 6. Excessive key-off current drain

Causes of Battery Failure All batteries have a limited life, but some

conditions can shorten that life.

1.ELECTROLYTE LEVEL: A low electrolyte level exposes active material, and any sulfate hardens and resists chemical action.

Loss of electrolyte may be caused by a cracked case, poor maintenance (not adding water when needed).

Severe overcharging which causes high internal heat and excessive gassing.

Too much electrolyte is just as bad. Overfilling dilutes the electrolyte and spillage may corrode battery terminals.

Causes of Battery Failure

2.OVERCHARGING: Overcharging by the vehicle's charging system or separate battery charger causes excessive gassing and high internal heat. Too much gassing can wash active materials off the plates, as well as cause excessive water usage. Too much heat can oxidize the positive plate material and warp the plates.

3.UNDERCHARGING: A faulty charging system will not maintain the

battery at full charge. Severe undercharging allows sulfate on the plates to become hard and impossible to remove by normal charging. The weak electrolyte freezes easier. The undercharged battery may fail to crank the engine.

4.CYCLING: Repeated cycling from fully charged to fully discharged and back - may cause loss of active material from the positive plates. This reduces battery capacity and its useful life.

Causes of Battery Failure

5. TEMPERATURE: High temperatures from overcharging or engine heat can shorten battery life.

Low temperatures can cause freezing of weak electrolyte. At 0F (-17.8°C), a fully charged battery provides less than half its normal power.

At the same time, the cold engine requires twice as much cranking power as it does with normal temperatures.

The electrolyte in a fully charged battery will not freeze until -60°F or lower, while the electrolyte in a fully dis charged battery will freeze at + 18°F.

6. VIBRATION: A battery must be mounted securely. Vibration can loosen connections, crack the case, and damage internal components.

Testing the Battery

Testing is done to determine whether a battery: 1. Is in good condition 2. Needs recharging 3. Is defective and should be discarded 4. To test the state of charge

- hydrometer for vent-cap battery - charge indicator for maintenance-free battery

5. To test for performance - battery load test

Electrolyte SG Test : Hydrometer

Uses a hydrometer to measure the specific gravity of the electrolyte.

By measuring the specific gravity of the electrolyte, it tell if the battery is fully charged, requires charging, or must be replaced.

Read the specific gravity indicated on the float. Be sure the float is drifting free, not in contact with the sides of top of the barrel.

TEST RESULTS: 1. A fully charged battery will have specific gravity readings around 1.265.2. Specific gravity readings below 1.225 usually mean the battery is run down and must be charged.

Open-Circuit Voltage Test

An accurate digital voltmeter is used to check the battery's open-circuit voltage:

1 . If the battery has just been charged, turn on the headlamps for one minute to remove any surface charge.

2. Turn headlamps off and connect the voltmeter across the battery terminals.

3. Read the voltmeter. A fully charged battery will have an open-circuit voltage of at least 12.6 volts. A dead battery will have an open-circuit voltage of less than 12.0 volts.

Battery Drain Test (Leak current) Check for battery drain or leak current using an

ammeter. Connect the ammeter in series between the battery

negative terminal and ground cable connector. Common vehicles typically show less than .020 amp of

current to maintain electronic memories. A reading of more than .035 amp is unacceptable. If the

ammeter reads more than .035 amp, locate and correct the cause of excessive battery drain.

Excessive battery drain

Charge-indicator Condition It is a built-in hydrometer to show

the condition and state of charge of the battery.

A green indication means the battery is over 65% charged.

If indicator is dark, the battery is less than 65% charged- the battery should be charge.

If the indicator is light yellow or clear, the electrolyte level is low- if it happen to a maintenance-free battery, replace the battery.

After the battery passes the state of charge test, check for the performance by battery capacity test or battery load test. This measures terminal voltage while the battery is discharging at high rate.

To perform the test; 1. The load is applied using a tester (Sun VAT-40) that includes a

voltmeter, an ammeter and a carbon-pile resistor. 2. Load the battery by turning the Load Increase control until the

ammeter reads 3 times the amp- hour (AH) rating or one-half the cold-cranking ampere (CCA) rating.

3. After 15 seconds, read the voltage and remove the load. Battery voltage should read 9.6 volts or higher.

4. If below the minimum, recharge the 5. battery and retest it. If fails again, discard the battery

Heavy-Load test

Battery Charging A battery charger must be used if the alternator cannot charge

the battery adequately due to long period of no use.

Slow Charging A slow charger feeds small amount of current into the battery.

Charging time is longer (about 12 hours at 10 amps). The chemical action inside the battery is improved and the

active materials are plated back on the battery plates better.

Fast Charging /Boost Charging A fast charger forces a high current flow into the battery for

rapid recharging. Fast charging allow engine starting in a matter of minutes. A high charging current can be used below the gassing voltage.

If exceeded, the battery starts to gas and leads to water loss in battery.

Done for emergency case only because it can cause damage to battery

FACTORS AFFECTING CHARGING Five factors affect battery charging;

FACTORS AFFECTING CHARGING

1. TEMPERATURE: As the temperature decreases the electrolyte resists charging. A cold battery will take more time to charge; a warm battery, less time. Never attempt to charge a frozen battery.

 2. STATE-OF-CHARGE: The condition of the battery's active materials will

affect charging. A battery that is severely discharged will have hard sulfate crystals on its plates. The vehicle's charging system may charge at too high of a rate to remove such sulfates.

 3. PLATE AREA: Small plates are charged faster than large plates. When

sulfation covers most of the plate area, the charging system may not be able to charge the battery.

4. IMPURITIES: Dirt and other impurities in the electrolyte increase charging difficulty.

 5. GASSING: Hydrogen and oxygen bubbles form at the plates during

charging. As these bubble out, they wash away active material, cause water loss, and increase charging difficulty.

Charging rate

Jump-starting Proper connections in jump starting a dead battery with a

booster battery to prevent sparks. 1. First, connect cable(red) to the two positive terminals. 2. Then, connect one end of the jumper cable (black) to the

negative terminal of the booster battery. 3. Connect the other end to a good ground away from the

dead battery. 4. If a spark occurs, it won't be near the battery.

Battery Storage

For new battery; 1. Unfilled: unlimited 2. Filled, conventional: 3 (max 6) months 3. Filled, completely maintenance-free: 18 months 4. Battery must be stored in a cool and dry place and

in a good state of charge 5. Do not stack batteries on top of each other without

additional support, because the weight can collapse the case and the plates in the bottom battery will bend.

Removing and Replacing BatteryTo remove a battery: 1. Disconnect the ground cable from the battery 2. Loosen the clamp bolt then pull the clamp from the terminal 3. If the clamp sticks, use a battery-clamp puller 4. Disconnect the positive cable from the battery 5. Remove the battery

To install the battery:

1. Do not reverse the terminal connections

2. Reconnect the positive cable first then the

ground cable

3. Tighten the hold-down clamps but do not

over-tighten

THE END

Any question?

Assignment

Differentiate between battery slow charging and fast charging, and give an advantages and disadvantages of each methods.