Manual Drivetrains and Axles Fourth Edition

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start
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OBJECTIVES
After studying Chapter 39, the reader should be
able to

• Describe how a battery works.
• List the precautions necessary whenever working
  with batteries.
• Explain how to safely charge a battery.
• Discuss how to perform a battery drain test.

3
KEY TERMS

• absorbed glass mat (AGM) battery ampere-hour
  (Ah) rating antimony
• battery electrical drain test BCI
• calcium cells cold-cranking amperes (CCA)
  conductance testing cranking amperes (CA)
• deep cycling dynamic voltageelectrolyte
  element
• flooded cell battery

Continued
4
KEY TERMS

• gassing gell battery gridsignition off draw
  (IOD) test
• jump-starting
• lead dioxide (peroxide) lead sulfate load
  test low-water-loss battery
• maintenance-free battery marine cranking
  amperes (MCA) meniscus
• open circuit battery voltage test

Continued
5
KEY TERMS

• parasitic load test partitions pasting
  porous leadradial-grid design recombinant
  design battery reserve capacity (RC)
• sealed lead-acid (SLA) battery sealed valve
  regulated (SVR) battery sediment chamber
  separators specific gravity sponge lead
• valve regulated lead-acid (VRLA) battery

6

• Everything electrical in a vehicle receives its
  current from the battery.
• The battery is one of the most important parts
  of a vehicle and is the foundation for the entire
  electrical system.

7
PURPOSE OF A BATTERY

• The primary purpose of an automotive battery is
  to provide a source of electrical power for
  starting and for electrical demands that exceed
  generator output. The battery is a voltage
  stabilizer because it acts as a reservoir where
  large amounts of current (amperes) can be removed
  quickly during starting and replaced gradually by
  the generator during charging.The battery must
  be in good (serviceable) condition before the
  charging system and the cranking system can be
  tested. It is important to test the vehicle
  battery before further testing of the cranking or
  charging system.

8
BATTERY CONSTRUCTION

• 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.

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.
Figure 391 Batteries are constructed of plates
grouped into cells, installed in a plastic case.
This sediment chamber, prevents spent material
from causing a short circuit between the plates
at the bottom of the battery.
Continued
9
GRIDS

• 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.

Continued
10

• 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.

Continued
11
Figure 392 A radial grid from a battery used in
both positive and negative plates.

• 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 radial spokes act as a superhighway system
for the current to travel from all areas of the
grid to the battery post.
Continued
12

• 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

Continued
13

• 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)
  thebattery could produce would be increased.

Continued
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• 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.
• See Figure 393.

Continued
15
Figure 393A cutaway battery showing the
connection of the cells to each other through the
partition.
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.

• Some water (H2O) escapes during charging as a
  result of the gassing produced by the chemical
  reactions.

Only pure distilled water should be added to a
battery. If distilled water is not available,
clean drinking water can be used.
16

• 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.

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HOW A BATTERY WORKS

• 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).

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Figure 394 Chemical reaction for a lead-acid
battery that is fully charged being discharged by
the attached electrical load.
Continued
19

• The 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 (H2O). It is usually
  not possible for a battery to become 100
  discharged. However, as the battery is being
  discharged, the plates and electrolyte approach
  the completely dead situation. There is also the
  danger of freezing when a battery is discharged,
  because the electrolyte is mostly water.During
  Charging The sulfate ion (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 (PbO2) and the negative
  plate is again pure lead (Pb).See Figure 395.

Continued
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Figure 395 Chemical reaction for a lead-acid
battery that is fully discharged being charged by
the attached generator.
Continued
21
A battery engineer explains to the employees
of the plant how a battery works using these very
easy-to-remember statements When the battery
is being discharged, the acid leaves the liquid
and is de-posited on the plates. When the battery
is being charged, the current flows into the
battery, forcing the acid from the plate and back
into the liquid (electrolyte).
An Easy Way to Remember Battery Chemical Reactions

• When the battery is charged, the acid (SO4 ) is
  in the liquid.
• When the battery is discharged, the acid (SO4 )
  is on the plates.

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SPECIFIC GRAVITY

• Sulfate in the electrolyte is indicated by the
  electrolytes specific gravity, the ratio of
  weight of a given volume of a liquid to the
  weight of an equal volume of water.The more
  dense the material (liquid), the higher its
  specific gravity. Pure water is the basis for
  this measurement and is given a specific gravity
  of 1.000 at 80F.Pure sulfuric acid has a
  specific gravity of 1.835 the correct
  concentration of water and sulfuric acid (called
  electrolyte64 water, 36 acid) is 1.260 to
  1.280 at 80F.The higher the batterys specific
  gravity, the more fully it is charged. See Figure
  396.

Continued
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Figure 396 As the battery becomes discharged,
the specific gravity of the battery acid
decreases.
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CHARGE INDICATORS

• Some batteries are equipped with a built-in
  state-of-charge indicator.This indicator is
  simply a small ball-type hydrometer that is
  installed in one cell.

When the ball floats, it appears in the
hydrometers sight glass, changing its color.
Figure 397Typical battery charge indicator. If
the specific gravity is low (battery discharged),
the ball drops away from the reflective prism.
When the battery is charged enough, the ball
floats and reflects the color of the ball
(usually green) back up through the sight glass
and the sight glass is dark.
25
Figure 398 Cutaway of the battery showing the
charge indicator. If the electrolyte level drops
below the bottom of the prism, the sight glass
shows clear (light). Most battery manufacturers
warn that if the electrolyte level is low on a
sealed battery, the battery must be replaced.
Attempting to charge a battery that has a low
electrolyte level can cause a buildup of gases
and possibly an explosion.

• This hydrometer uses a plastic ball that floats
  if electrolyte density is sufficient (when the
  battery is about 65 charged).

Because it is only testing one cell out of six,
and because the hydrometer ball can easily stick
in one position, it should not be trusted to give
accurate data about a batterys charge.
Continued
26

• Specific Gravity versus State of Charge and
  Battery Voltage Values of specific gravity, state
  of charge, and battery voltage at 80F (27C) are
  shown here

See this chart on Page 406 of your textbook.
27
VALVE-REGULATED LEAD ACID BATTERIES

• There are two basic types of valve regulated
  lead-acid (VRLA), also called sealed valve
  regulated (SVR) or sealed lead-acid (SLA),
  batteries. They use a low-pressure venting system
  that releases excess gas and automatically
  reseals if a buildup of gas is created due to
  overcharging. The two types include the following

• Absorbed glass mat (AGM) The acid used in an
  absorbed glass mat (AGM) battery is totally
  absorbed into the separator, making the battery
  leakproof and spillproof. The battery is
  assembled by compressing the cell about 20 then
  inserting it into the container. The compressed
  cell helps reduce damage caused by vibration and
  helps keep the acid tightly against the plates.

Continued
28
Figure 399 An absorbed glass mat battery is
totally sealed and is more vibration resistant
than conventional lead-acid batteries.

• Unlike conventional batteries, called flooded
  cell batteries, most of the hydrogen and oxygen
  given off during charging remains inside the
  battery. AGM batteries also have a longer service
  life, often lasting 7 to 10 years.

Absorbed glass mat batteries are used as standard
equipmentin vehicles such asthe Chevrolet
Corvette.
Continued
29

• Gelled electrolyte batteries. In a gelled
  electrolyte battery, silica is added to the
  electrolyte, which turns the electrolyte into a
  substance similar to gelatin. This type of
  battery is also called a gel battery.

Both types of valve regulated lead-acid batteries
are also called recombinant design, which means
oxygen gas generated at the positive plate
travels through dense electrolyte to the negative
plate.When the oxygen reaches the negative
plate it reacts with the lead, which consumes the
oxygen gas and prevents the formation of hydrogen
gas.It is because of this oxygen recombination
that VRLA batteries do not use water.
30
All batteries should be stored in a cool, dry
place when not in use. Many technicians have been
warned to not store or place a battery on
concrete. According to battery experts, it is
the temperature difference between the top and
the bottom of the battery that causes a
difference in the voltage potential between the
top (warmer section) and the bottom (colder
section). It is this difference in temperature
that causes self-discharge to occur. In fact,
submarines cycle seawater around their batteries
to keep all sections of the battery at the same
temperature to help prevent self-discharge.Alway
s store or place batteries up off the floor and
in a location where the entire battery can be
kept at the same temperature, avoiding extreme
heat and freezing temperatures. Concrete cannot
drain the battery directly, because the case of
the battery is a very good electrical insulator.
Should Batteries Be Kept Off Concrete Floors?
31
BATTERY HOLD-DOWNS

• All batteries must be attached securely to the
  vehicle to prevent battery damage. Normal vehicle
  vibrations can cause the active materials inside
  the battery to shed. Battery hold-down clamps or
  brackets help reduce vibration, which can greatly
  reduce the capacity and life of any battery.

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BATTERY RATINGS

• Batteries are rated according to the amount of
  current they can produce under specific
  conditions.

Cold-Cranking Amperes Every automotive battery
must be able to supply power to crank the engine
in cold weather and provide voltage high enough
to operate the ignition system for starting.The
cold-cranking power of a battery is the number of
amperes that can be supplied by a battery at 0F
(?18C) for 30 seconds while the battery still
maintains a voltage of 1.2 volts per cell or
higher.Cold-cranking performance rating is
called cold-cranking amperes (CCA). Try to
purchase a battery with the highest CCA for the
money. See vehicle specifications for recommended
capacity.
Continued
33

• Cold-Cranking Amperes Every automotive battery
  must be able to supply electrical power to crank
  the engine in cold weather and still provide
  battery voltage high enough to operate the
  ignition system for starting.The cold-cranking
  power of a battery is the number of amperes that
  can be supplied by a battery at 0F (?18C) for
  30 seconds while the battery still maintains a
  voltage of 1.2 volts per cell or higher.This
  means that the battery voltage would be 7.2 volts
  for a 12-volt battery and 3.6 volts for a 6-volt
  battery.Cold-cranking performance rating is
  called cold-cranking amperes (CCA). Try to
  purchase a battery with the highest CCA for the
  money. See vehicle specifications for recommended
  capacity.

Continued
34
Every automotive battery has a limited service
life of approximately three to seven years.
During the life of a battery, the active material
sheds from the surface of the positive
plates.This gradually limits the power of the
battery. This cycling also can cause the negative
plates to become sulfated, which will also cause
eventual battery failure. Excessive parasitic
drains also can cause a battery to fail
prematurely due to constant deep cycling of the
battery.
What Causes a Battery to Wear Out?
NOTE A battery becomes sulfated when lead
sulfate (SO4) remains on the plates and does not
return to electrolyte when the battery is charged.
35
Figure 3910 This battery has a cranking amperes
(CA) rating of 1000. This means that this battery
is capable of cranking an engine for 30 seconds
at a temperature of 32F (0C) at a minimum of
1.2 volts per cell (7.2 volts for a 12-volt
battery).

• Cranking Amperes The designation CA (cranking
  amperes) refers to the number of amperes that can
  be supplied by a batteryat 32F (0C). This
  rating results in a higher number than the more
  stringent CCA rating.

Continued
36

• Ampere-hour Rating Marine cranking amperes (MCA)
  are similar to cranking amperes and tested at
  32F (0C). Another type of rating is the
  ampere-hour (Ah) rating, which is the number of
  amperes that can be discharged from the battery
  before dropping at 10.5 volts over a 20-hour
  period. A able to supply 3.75 amperes for 20
  hours has a rating of 75 ampere-hours (3.75 ? 20
  5 75).Reserve Capacity The reserve capacity
  (RC) rating for batteries is the number of
  minutes for which the battery can produce 25
  amperes and still have a battery voltage of 1.75
  volts per cell (10.5 volts for a 12-volt
  battery).This rating is actually a measurement
  of the time for which a vehicle can be driven in
  the event of a charging system failure.

Continued
37
The capacity of any battery is determined by
the amount of active material in the battery. A
battery with a large number of thin plates can
produce high current for a short period. If a few
thick plates are used, the battery can produce
low current for a long period.A trolling motor
battery used for fishing must supply a low
current for a long period of time. An automotive
battery is required to produce a high current for
a short period for cranking. Therefore, every
battery is designed for a specific application.
What Determines Battery Capacity?
38
DEEP CYCLING

• Deep cycling is almost fully discharging a
  battery and then completely recharging it.Golf
  cart batteries are an example of lead-acid
  batteries that mustbe designed to be deep
  cycled. A golf cart must be able to covertwo
  18-hole rounds of golf and then be fully
  recharged overnight.Charging is hard on
  batteries because the internal heat generated can
  cause plate warpage, so these specially designed
  batteries use thicker plate grids that resist
  warpage.Normal automotive batteries are not
  designed for repeated deep cycling.

39

What Can Cause a Battery to Explode? - Part 1

• Batteries discharge hydrogen gas and oxygen when
  being charged. If there happens to be a flame or
  spark, the hydrogen will burn. The oxygen can
  also help contribute to an explosion of a small
  pocket of hydrogen. This is likely what happened
  to the battery in Figure 3911, when the battery
  charger was left on the battery over 24 hours.
  Apparently, a small electrical arc occurred
  inside the battery and the resulting explosion
  sounded like a shotgun being fired.

Figure 39-11 (a) A small spark inside the battery
was the most likely cause of this battery
explosion. Parts of the battery were thrown 30
feet (10 m). Luckily no one was around the
vehicle at the time.
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Figure 39-11 (b) Because battery acid was spilled
and sprayed around the battery, the entire area
was rinsed with water after unplugging the
battery charger.

What Can Cause a Battery to Explode? - Part 2
41
There are several warning signs that may
indicate that a battery is near the end of its
useful life, including
What Are Some Symptoms of a Weak or Defective
Battery? - Part 1

• Uses water in one or more cellsThis indicates
  that the plates are sulfated and that during the
  charging process, the water in the electrolyte is
  being turned into hydrogen and oxygen gases.
• Excessive corrosion on battery cables or
  connectionsCorrosion is more likely to occur if
  the battery is sulfated, creating hot spots on
  the plates.
• Slower than normal engine crankingWhen the
  capacity of thebattery is reduced due to damage
  or age, it is less likely to be ableto supply
  the necessary current for starting the engine,
  especiallyduring cold weather.

42

Symptoms? - Part 2

• When the battery is being charged, the acid fumes
  are forced out of the vent holes and get onto the
  battery cables and connections and even on the
  battery tray underneath the battery.

Figure 3912Corrosion on a battery cable could
be an indication thatthe battery itself is
either being overcharged or is sulfated, creating
a lot of gassing of the electrolyte.
43
BATTERY SERVICE SAFETY CONSIDERATIONS

• Batteries contain acid and release explosive
  gases (hydrogen and oxygen) during normal
  charging and discharging cycles. To prevent
  physical injury or vehicle damage, adhere to the
  following

1. Whenever working on any electrical component on a
   vehicle, disconnect the negative battery cable
   from the battery.When the negative cable is
   disconnected, all electrical circuits in the
   vehicle will be open, which will prevent
   accidental electrical contact between an
   electrical component and ground.Any electrical
   spark has the potential to cause explosion and
   personal injury.

Continued
44

1. Wear eye protection whenever working around any
   battery.
2. Wear protective clothing to avoid skin contact
   with battery acid.
3. Always adhere to all safety precautions as stated
   in the service procedures for equipment used for
   battery serviceand testing.
4. Never smoke or use an open flame around any
   battery. .

45
BATTERY MAINTENANCE

• Most new-style batteries are of maintenance-free
  design that use lead-calcium instead of
  lead-antimony plate grid construction.Because
  lead-calcium batteries do not release as much gas
  as the older-style lead-antimony batteries, there
  is less consumption of water during normal
  service.Also, with less gassing, less corrosion
  is observed on the battery terminals, wiring, and
  support trays. Side-terminal battery design also
  has reduced the self-discharge that can often
  occur as a result of dirt and moisture on the top
  of the battery, which provide a conductive path
  for the current to flow between the terminals
  that can lead to battery discharge.

Continued
46
Figure 3913 A visual inspection on this battery
showed that the electrolyte level was below the
plates in all cells.

• Battery maintenance includes making certain the
  battery case is clean, checking and adding clean
  water if necessary.

Distilled water is recommended by all battery
manufacturers.
If distilled water is not available, clean
ordinary drinking water, low in mineral content,
can be used.
Continued
47

• Because water is the only thing in a battery that
  is consumed, acid should never be added to a
  battery. Battery electrolyte is an exact mixture
  of acid and water (64 water and 36 acid).Some
  water in the electrolyte escapes during normal
  operation of charging and discharging, but acid
  content of the electrolyte remains in the
  battery. Adding electrolyte increases the acid
  content of the electrolyte and will shorten the
  life of the battery.Do not overfill a battery,
  because normal gassing will cause the electrolyte
  to escape and start corrosion on battery
  terminals, hold-down brackets, and tray. Fill
  batteries to until the water becomes puckered,
  indicating the electrolyte level is even with the
  bottom of the filler tube. This puckering of
  water in a tube is called the meniscus.

Continued
48

• The battery should be secured with a hold-down
  bracket to prevent vibration from damaging the
  plates inside the battery. Factory-original
  hold-down brackets are often available through
  local automobile dealers, and universal hold-down
  units are available through local automotive
  parts stores.Battery cable connections should
  be checked and cleaned to prevent voltage drop at
  the connections. One common reason for an engine
  to not start is loose or corroded battery cable
  connections. Replacement battery cable terminal
  ends are available at most automotive parts
  stores.

49
Open circuit voltage is the voltage (usually of
a battery) that exists without a load being
applied. Dynamic voltage is the voltage of the
power source (battery) with the circuit in
operation.A vehicle battery, for example, may
indicate it has 12.6 volts or more, but voltage
may drop when the battery is put under a load
such as cranking the engine. If battery voltage
drops too much, the starter motor will rotate
more slowly and the engine may not start. If
dynamic voltage is lower than specified, the
battery may be weak or defective or the circuit
may be defective, resulting in too much current
being drawn from the battery.
Dynamic versus Open Circuit Voltage
50
BATTERY VOLTAGE TEST

• Testing the battery voltage with a voltmeter is a
  simple method for determining the state of charge
  of any battery. See Figure 3914.The voltage of
  a battery does not necessarily indicate whether
  the battery can perform satisfactorily, but it
  does indicate to the technician more about the
  batterys condition than a simple visual
  inspection.A battery that looks good may not
  be good. This test is commonly called an open
  circuit battery voltage test because it is
  conducted with an open circuitwith no current
  flowing and no load applied to the battery.

Continued
51
Figure 3914 (a) A battery voltage of 12.28
volts is definitely not fully charged and should
be charged before testing. (b) A battery that
measures 12.60 volts or higher after the surface
charge has been removed is 100 charged.
(a)
(b)
Continued
52
Open Circuit Battery Voltage Test

1. If the battery has just been charged or if the
   vehicle has been driven recently, it is necessary
   to remove the surface charge from the battery
   before testing. A surface charge is a charge of
   higher-than-normal voltage that is just on the
   surface of the battery plates.
2. To remove the surface charge, turn the headlights
   on high beam (brights) for 1 minute, then turn
   the headlights off and wait2 minutes.
3. With the engine and all electrical accessories
   off, and the doors shut (to turn off the interior
   lights), connect a voltmeter to the battery
   posts. Connect the red positive lead to the
   positive post and the black negative lead to the
   negative post.

Continued
53

1. Read the voltmeter and compare the results with
   the following state-of-charge chart. The voltages
   shown are for a battery at or near room
   temperature (70 to 80F or 21 to 27C).

NOTE If the meter reads negative, the battery
has been reverse charged (has reversed polarity)
and should be replaced, or the meter has
been connected incorrectly.
See the chart on Page 409 of your
textbook.
54
Figure 3915 When testing a battery using a
hydrometer, the reading must be corrected if the
temperature is above or below 80F (27C).
HYDROMETER TESTING

• If the battery has removable filler caps, the
  specific gravity of the electrolyte also can be
  checked.

The specific gravity test indicates thecharge
stateof the battery
Continued
55
This test also can be performed on most
maintenance-free batteries because the filler
caps are removable from most maintenance-free
batteries (except for Delco).

• It can indicate a defective battery if the
  specific gravity of one or more cells varies by
  more than 0.050 from the value of the
  highest-reading cell.

See the chart on Page 410 of your textbook.
56
BATTERY LOAD TESTING

• The most accurate test to determine the condition
  of any battery is the load test. Most starting
  and charging testers use a carbon pile to create
  an electrical load on the battery. The amount of
  the load is determined by the original capacity
  of the battery being tested.

Figure 3916 This battery has cold-cranking
amperes (CCA) of 550 A, cranking amperes (CA) of
680 A, and load test amperes of 270 A listed
right on the top label. Note all batteries have
all of this information.
The proper electrical load to be used to test a
battery is one-half of the CCA rating or three
times the ampere-hour rating, with a minimum of a
150-ampere load.
Continued
57
A high-rate battery load test should take one
minute.
The One-Minute Test

• Load for 15 seconds to remove the surface charge.
• Allow 30 seconds for the battery to recover.
• Load for 15 seconds to test the battery.

Apply the load for a full 15 seconds and observe
the voltmeter atthe end of the 15-second period
while the battery is still under load.Wait 30
seconds between tests to allow time for the
battery to recover. If the battery fails the load
test, recharge the battery and retest. If the
load test is failed again, replacement is
required.
Continued
58
Figure 3917 An alternator regulator battery
starter tester (ARBST) automatically loads the
battery with a fixed load for 15 seconds to
remove the surface charge, then removes the load
for 30 seconds to allow the battery to recover,
and then reapplies the load for another 15
seconds. The results of the test are then
displayed.
Continued
59
Figure 3918 The minimum capacity test voltage
varies with battery temperature.

• A good battery should indicate above 9.6 V. Many
  manufacturers recommend performing the test
  twice, using the first load period to remove the
  surface charge on the battery and the second test
  to provide a truer indication of the condition of
  the battery.

See the chart on Page 411 of yourtextbook.
60
Many vehicles equipped with a diesel engine
use two batteries. Usually these batteries are
electrically connected in parallel to provide
additional current (amperes) at the same voltage.
How Should You Test a Vehicle Equipped With Two
Batteries? - Part 1
To successfully test the batteries, they should
be disconnected and tested separately. If just
one battery is found to be defective, most
experts recommend that both batteries be replaced
tohelp prevent future problems.
Figure 3919 Most light-duty vehicles equipped
with two batteries are connected in parallel as
shown. Two 500-A, 12-volt batteries are capable
of supplying 1,000 amperes at 12 volts, which is
needed to start many diesel engines.
61

How Should You Test a Vehicle Equipped With Two
Batteries? - Part 2
Because the two batteries are electrically
connected, a fault in one battery can cause the
good battery to discharge into the defective
battery, affecting both batteries even if just
one battery is at fault.
Figure 3920 Many heavy-duty trucks andbuses use
two 12-volt batteries connectedin series to
provide 24 volts.
62
ELECTRONIC CONDUCTANCE TESTING

• 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.

The tester determines the following

• Good batterythe battery can return to service
• Charge and retestfully recharge battery and
  return to service
• Replace the batterybattery not serviceable
  should replace
• Bad cellreplacebattery not serviceable should
  be replaced

Continued
63
Figure 39-21 A conductance-type battery tester.
(a) The up-and-down arrow keys are used to answer
questions about the battery before it is tested.
(b) This battery shows a calculated CCA of 729
amperes and a voltage of 12.37 volts. The display
indicates that the battery is good, but should be
charged before returning the vehicle to service.
(c) A test code is displayed for warranty
record-keeping purposes.
(c)
(a)
(b)
64
Figure 3922 Battery charging guide. Battery
charging times vary according to state-of-charge,
temperature, and charging rate.
BATTERY CHARGING

• If the state of charge of a battery is low, it
  must be recharged. It is best to slow-charge any
  battery to prevent possible overheating damage to
  the battery.

It may take 8 hours or more to charge a fully
discharged battery.
See the chart on Page 413 of your textbook.
Continued
65
CAUTION Always use a battery charger designed
for absorbed glass mat (AGM) batteries because
that type of battery can be damaged if charged
above 15.5 volts. While AGM batteries can be
charged at a high average rate (about 75 amp
hour rating) the voltage must be lower than the
conventional charger.
Most batteries should be charged at a rate equal
to 1 of the batterys CCA rating.
CAUTION Test results can be incorrectly
reported on the display if improper, unclean
connections to the battery are made. Also be sure
the ignition switch and all accessories are in
the off position.
Continued
66

• When charging a maintenance-free (lead-calcium)
  battery, the initial charge rate should be about
  35 amps for 30 minutes to help start the charging
  process.

Fast-charging increases the amountof gassing
(release of hydrogen and oxygen), which can be a
health andfire hazard.
It also increases the temperature ofthe battery
and can cause warpingof the plates inside the
battery.
Figure 3923 A typical industrial battery
charger. Be sure that the ignition switch is in
the off position before connecting any battery
charger. Connect the cables of the charger to the
battery before plugging the charger into the
outlet. This helps prevent a voltage spike that
could occur if the charger happened to be
accidentally left on. Always follow the battery
charger manufacturers instructions.
67

Always Use Adapters on Side-Post Batteries
Side-post batteries require an adapter to be used
whenever charging the battery if it is removed
from the vehicle. If a bolt is threaded into
the terminal, only the parts of the threads that
contact the battery terminal will be conducting
all of the charging current. An adapter or a
bolt with a nut attached is needed to achieve
full contact with the battery terminals.
Figure 3924 Adapters should be usedon
side-terminal batteries when charging.
68
JUMP-STARTING

• To jump-start another vehicle with a dead
  battery, connect good-quality copper jumper
  cables using another vehicle or a battery jump
  box.

Figure 3925 A typical battery jump box used to
jump-start vehicles. These hand-portable units
have almost made jumper cables obsolete.
The last connection should always be on the
engine block or on an engine bracket as far from
the battery as possible.
It is normal for a spark to be created when
jumper cables complete the jumping circuit, and
this spark could cause an explosion of battery
gases.
Continued
69

• Many newer vehicles have special ground
  connections built away from the battery just for
  the purpose of jump-starting.Check the owners
  manual or service information for the exact
  location.

CAUTION To help avoid the possibility of a
voltage surge causing damage to the computer or
electronic circuits of the vehicle, be sure that
the ignition is in the off position of both
vehicles before attaching the jumper cables.
After the last connection has been made, start
the good vehicle, and then start the disabled
vehicle.
70
BATTERY DATE CODES

• Major battery manufacturers stamp codes on the
  battery case that give date of manufacture and
  other information. Most use a number to indicate
  year of manufacture and a letter to indicate
  month of manufacture, skipping letter I, as it
  can be confused with number 1.

The shipping date is usuallyindicated by a
sticker toindicate month and year.
G July H August J September K October L
November M December
A January B February C March D April E
May F June
Figure 3926 The date 5/07 indicates that this
battery was shipped from the manufacturing plant
in May 2007.
Continued
71
After the owner of a Toyota replaced the
battery, the owner noted the amber airbag
warning lamp was lit and the radio was locked
out.
It Could Happen To You! - Part 1 of 3
The owner had purchased the vehicle used from a
dealer and did not know the four-digit security
code needed to unlock the radio. Determined to
fix the problem, the owner tried three four-digit
numbers, hoping one of them would work. After
three tries, the radio became permanently
disabled. Frustrated, the owner went to a dealer.
It cost over 300 to fix the problem.
A special tool was required to easily reset the
airbag lamp. The radio had to be removed and sent
out of state to an authorized radio service
center and then reinstalled into the vehicle.
Before disconnecting the battery, please check
with the owner to be certain that the owner has
the security code for a security-type radio. A
memory saver may be needed to keep the radio
powered up when the battery is being disconnected.
72
Figure 3927 (a) Memory saver. The part numbers
represent components from Radio Shack.
It Could Happen To You! - Part 2 of 3
73
Figure 3927(b)A schematic drawing of the same
memory saver. Some experts recommend using a
12-volt lantern battery instead of a small 9-volt
battery to help ensure that there will be enough
voltage in the event that a door is opened while
the vehicle battery is disconnected. Interior
lights could quickly drain a small 9-volt battery.
It Could Happen To You! - Part 3 of 3
74
BATTERY ELECTRICAL DRAIN TEST

• The battery electrical drain test determines if
  some component or circuit in a vehicle is causing
  a drain on the battery when everything is off.
  This test is also called the ignition off draw
  (IOD) or parasitic load test. This test should be
  performed whenever one of the following
  conditions exists

1. Whenever a battery is being charged or replaced
   (a battery drain could have been the cause for
   charging or replacing the battery)
2. Whenever the battery is suspected of being
   drained

75
PROCEDURE FOR BATTERY ELECTRICAL DRAIN TEST

• The fastest and easiest method to measure battery
  electrical drain is to connect an inductive DC
  ammeter that is capable of measuring low current
  (10 mA). Here is an example of a clamp-on digital
  multimeter being used to measure battery drain.

Figure 3928This mini clamp-on digital
multimeter is being used to measure the amount of
battery electrical drain that is present. In this
case, a reading of 20 mA (displayed on the meter
as 00.02A) is within the normal range of 20 to 30
mA. Be sure to clamp around all of the positive
battery cable or all of the negative battery
cable, whichever is easiest to get the clamp
around.
Continued
76
Figure 3929 After connecting the shutoff tool,
start the engine and operate all accessories.
Stop the engine and turn off everything. Connect
the ammeter across the shutoff switch in
parallel. Wait 20 minutes. This time allows all
electronic circuits to time out or shut down.
Open the switchall current now will flow through
the ammeter. A reading greater than specified
(usually greater than 50 milliamperes 0.05
amperes) indicates a problem that should be
corrected.

• Procedure for battery electrical drain test using
  a test light

1. Make certain that all lights, accessories, and
   ignition are off.
2. Check all vehicle doors to be certain that the
   interior courtesy (dome) lights are off.
3. Disconnect the negative (?)battery cable and
   install aparasitic load tool asshown here.
4. Start the engine, drivevehicle about 10 min,
   usinglights, accessories and radio.

Continued
77

1. Turn off the engine and all accessories including
   the under-hood light.
2. Connect an ammeter across the parasitic load tool
   switch and wait 10 minutes for all computers and
   circuits to shut down.
3. Open the switch on the load tool and read the
   battery electrical drain on the meter display.

Normal10 to 30 mA (0.02 to 0.03 A) Maximum
allowable50 mA (0.05 A)
Results
CAUTION Using a voltmeter to measure battery
drain is not recommended by most vehicle
manufacturers. The high internal resistance of
the voltmeter results in an irrelevant reading
that does not provide the technician with
adequate information about a problem.
Continued
78
Figure 3930The battery was replaced in this
Acura and the radio displayed code when the
replacement battery was installed. Thankfully,
the owner had the five-digit code required to
unlock the radio.

• Be sure to reset the clock and antitheft radio if
  equipped.

79
NOTE Many electronic components draw a
continuous, slight amount of battery current the
ignition is off. These components
include These components may cause a
voltmeter to read full battery voltage if it is
connected between the negative battery terminal
and the removed end of the negative battery cable.

1. Digital clocks
2. Electronically tuned radios for station memory
   and clock circuits (if the vehicle is so
   equipped)
3. The engine control computer (if the vehicle is so
   equipped), through slight diode leakage
4. The generator (alternator), through slight diode
   leakage.

80
FINDING THE SOURCE OF THE DRAIN

• If there is a drain, check and temporarily
  disconnect the following

1. Light under the hood
2. Glove compartment light
3. Trunk light

If after disconnecting all three of these
components the battery drain can draw more than
50 milliamperes (0.05 A), disconnect one fuse at
a time and leave it disconnected until the draw
is reduced.Continue to disconnect the
power-side wire connectors from each component
included in that particular circuit until the
test light goes off. The source of the battery
drain can then be traced to an individual
component or part of one circuit.
81
WHAT TO DO IF BATTERY DRAIN STILL EXISTS

• If all the fuses have been disconnected and the
  drain still exists, the source of the drain has
  to be between the battery and the fuse box.
  Common sources of drain under the hood include
  the following

1. The generator Disconnect generator wires and
   retest. If the excessive battery drain stops, the
   problem is a defective diode(s) in the generator.
2. The starter solenoid (relay) or wiring near its
   components. A common source of battery drain, due
   to high current flows and heat, which can damage
   wire or insulation.

82
HIDDEN BATTERIES

• Many vehicle manufacturers today place the
  battery under the backseat or under the front
  fender. Often, the battery is not visible even if
  it is located under the hood.

Whenever testing or jump-starting a vehicle, look
fora battery access point asshown here.
Figure 3931Many newer vehicles have batteries
that are sometimes difficult to find. Some are
located under plastic panels under the hood,
under the front fender, or even under the rear
seat. The jump-start instructions indicate that
the spare tire hold-down bolt is to be used as
the ground connection if jump-starting is
necessary.
83
A discharged or defective battery has lower
voltage potential than a good battery that is at
least 75 charged. A weak battery could prevent
the charging voltage from reaching the voltage
regulator cutoff point. This lower voltage could
be interpreted as indicating a defective
generator (alternator) and/or voltage regulator.
If the vehicle continues to operate with low
system voltage, the stator winding in the
generator (alternator) can be overheated, causing
alternator failure.
Why Should a Discharged Battery Be Recharged or
Replaced Before Further Testing?
84
BATTERY SYMPTOM GUIDE
See this guide on Page 416 of your textbook.
85
SUMMARY

1. Maintenance-free batteries use lead-calcium grids
   instead of lead antimony grids to reduce
   gassing.
2. When a battery is being discharged, the acid
   (SO4) is leaving the electrolyte and being
   deposited on the plates. When the battery is
   being charged, the acid (SO4) is forced off the
   plates and back into the electrolyte.
3. Batteries are rated according to CCA and reserve
   capacity.
4. All batteries should be securely attached to the
   vehicle with hold down brackets to prevent
   vibration damage.

Continued
86
SUMMARY
(cont.)

1. Batteries can be tested with a voltmeter to
   determine the state of charge.
2. A battery load test loads the battery to one-half
   of its CCA rating.
3. A good battery that is at least 75 charged
   should be able to maintain higher than 9.6 volts
   for the entire 15-second test period.
4. A battery drain test should be performed if the
   battery runs down.

87
end