12-Volt Batteries

Purpose of a battery

Is to provide a source of electrical power for starting and for electrical demands that exceed alternator output.

What is the heart or foundation of the electrical system?

The battery is one of the most important parts of a vehicle.

Why batteries are important

The battery also acts as a voltage stabilizer for the entire electrical system. The battery is a voltage stabilizer because it acts as a reservoir from where large amounts of current (amperes) can be used quickly during starting and replaced back gradually by the alternator during charging.

Why cant we tests the cranking system if the battery is discharged?

The cranking circuit (starter motor) could test as being defective because the battery voltage might drop below specifications.The charging circuit could also test as being defective because of a weak or discharged battery.It is important to test the vehicle battery before further testing of the cranking or charging system.

What is a SLI battery?

SLI means starting, lighting and ignition, and describes the use of a typical automotive battery. Other types of batteries used in industry are usually batteries designed to be deep cycled and are usually not as suitable for automotive needs.

Most automotive battery cases (container or covers) are constructed of

Polypropylene, a thin (approximately 0.08 in or 0.02 millimeter thick) strong and lightweight plastic.In contrast, containers for industrial batteries and some truck batteries are constructed of a hard,thick rubber material.

Sediment chamber

A space below the cell plates of some batteries to permit the accumulation of sediment deposits flaking from the battery plates. Keeps the sediment from shorting the battery plates.

Battery grids

Hold the active material and provide the electrical pathways for the current created in the plate. Each positive and negative plate in a battery is constructed on a framework or grid made primarily of lead.

Grid

The lead-alloy framework (support) for the active materials of an automotive battery. Adding antimony or calcium to the pure leads adds strength to the lead grids.

lead

Is a soft material and must be strengthened for use in an automotive battery grid.

Maintenance-free battery uses

Little water during normal service because of the alloy material used to construct the battery plates grids.Maintenance-free battery grids use calcium instead of antimony.

How much does a typical lead-calcium grid uses?

Only 0.09% to 0.12% calcium.

Gassing

Is the release of hydrogen and oxygen from the battery that occurs during charging and results in water usage.Using low amount of calcium instead of higher amount of antimony reduces gassing.The release of hydrogen and oxygen gas from the plates of a battery during charging or discharging.

Low-maintenance batteries use

A low percentage of antimony of use antimony only in the positive grids and calcium in the negative grids.

The percentage that make up the alloy of the plate grids constitute the

Major difference between standard and maintenance-free batteries.The chemical reactions that occur inside each battery are identical, regardless of the type of material used to construct the grid plates.

Positive plates

Have lead dioxide(peroxide) 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

Are pasted to the grid with a pure porous lead, called sponge lead, and are gray in color.

Porous lead

Lead with many small holes to make a surface porous for use in battery negative plates;the chemical symbol for lead is Pb.

Separators

The positive and the negative plates must be installed alternately next to each other without touching.Nonconducting separators are used, which allow room for the reaction of the acid with both plate materials, yet insulate the plated to prevent shorts.These separators are porous (with many small holes) and have ribs facing the positive plate.Separators can be made from resin-coated paper, porous rubber,fiberglass,or expand plastic.Many batteries use envelope-type separators that encase the entire plate.This helps prevent any material that may shed from the plates from causing a short circuit between plates at the bottom of the battery.

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. A cell is also called an element. 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.

Typical batteries contain

4 positive plates and 5 negative plates per cell.

12-volt batteries contain

6 cells connected in series, which produce 12.6v and contain 54 plates. If the same 12-volt battery had 5 positive plates and 6 negative plates,for a total of 11 plates per cell, or 66 plates, it has the same voltage, but the amount of current that the battery could produce is increased.

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

Partitions

Each cell is separated from the other cells by partitions, which are made of the same material as that used for 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 provide the shortest path for the current and the lowest resistance.

Electrolyte

Is the term used to describe the acid solution in a battery.The electrolyte used in automotive batteries is a solution (liquid combination) of 36% sulfuric acid and 64% water.Is used for both lead-antimony and lead-calcium (maintenance-free) batteries.Electrolyte is sold premixed in a proper proportion and is factory installed or added to the battery when the battery is sold.It is normal for some water to escape during charging as a result of 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.

The chemical symbol for sulfuric acid solution is

H₂SO₄

• H₂ = Symbol for hydrogen (the subscription 2 means that there are two atoms of hydrogen)

• S= Symbol for sulfur

• O₄ = Symbol for oxygen (the subscript 4 indicates that there are four atoms of oxygen)

The principle of which a battery works is based on a scientific principle discovered years ago, which states that

• 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 of solid copper wire into a lemon.Connect a voltmeter to the ends of the copper wire and the nail, and voltage is displayed.

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

During Discharging

The positive plate lead dioxide (PbO₂) combines with the SO₄, forming PbSO₄ from the electrolyte and releases its 0₂ into the electrolyte,forming H₂O. The negative plate also combines with the SO₄ from the electrolyte and becomes lead sulfate (PbSO₄)

Fully discharged state

When the battery is fully discharged,both the positive and the negative plates are PBSO₄ and the electrolyte has become water. As the battery is being discharged, the plates and the electrolyte approach the completely discharged state.There is also the danger of freezing when a battery is discharged because the electrolyte is mostly water.

During Charging

The sulfate from the acid leavers both the positive and the negative plates and returns to the electrolyte, where it becomes a normal-strength sulfuric acid solution.The positive plate returns to lead dioxide, the negative plates is agina pure lead, and the electrolyte becomes H₂SO₄

Specific Gravity

The ratio of the weight of a given volume of a liquid divide by the weight of an equal volume of water.

The amount of sulfate in the electrolyte is determined by

The electrolyte’s specific gravity.

The denser the liquid,

The higher its specific gravity. Pure water is the basis for this measurement and is given a specific gravity of 1.000 at 80^o F(27 C).Pure sulfuric acid has a specific gravity of 1.835; the correct concentration of water and sulfuric acid (called electrolyte-64% water 36% acid) is 1.260 to 1.280 at 80^o F.The higher the battery’s specific gravity, the more fully it is charged.

Charge Indicators

Some batteries are equipped with a built-in state-of-charge indicator, commonly called green eyes.This indicator is simply a small, ball-type hydrometer that is installed in one cell.This hydrometer uses a plastic ball that floats if the electrolyte density is sufficient (which it is when the battery is about 65% charged).When the ball floats, it appears in the hydrometer’s sight glass, changing its color.

Why not trust the hydrometer to give an accurate information about a state of charge (SOC) of the battery?

Becuase the hydrometer is testing only one cell (out of sic on 12-volt battery) and because the hydrometer ball can easily stick in one position.

Flooded batteries

Conventional batteries use a liquid electrolyte and are called flooded lead acid (FLA) batteries.In this design, vent are used to allows the gases to escape.It is this loss of the hydrogen and oxygen that results in a battery using water during normal use.

Enhance Flooded Batteries (EFB)

is a flooded battery (NOT an absorbed glass mat battery) that is optimized to work with stop/start vehicle systems. Using wet cells, the design allows for improved charge acceptance and greater durability when being operated in a vehicle that uses a stop/start system. In stop/start vehicle, the engine stops running when at idle speed, then restarts when the driver releases the brake pedal. This operation requires a robust battery and starter motor to function correctly over an estimated life of over 500,000 stops and starts.

Absorbed Glass Mat (AGM)

The acid used in an absorbed glass mat (AGM) battery is totally absorbed into the separator, making the battery leak proof and spill proof. 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. The sealed maintenance-free design uses a pressure release valve in each cell. Unlike conventional batteries that use a liquid electrolyte, called flooded cell batteries, most of the hydrogen and oxygen given off during charging remains inside the battery. The separator or mat is only 90% to 95% saturated with electrolyte, thereby allowing a portion of the mat to be filled with gas. The gas spaces provide channels to allow the hydrogen and oxygen gases to recombine rapidly and safely. Because the acid is totally absorbed into the glass mat separator, an AGM battery can be mounted in any direction. AGM batteries also have a longer service life, often lasting 7 to 10 years. Absorbed glass mat batteries are used as standard equipment in some vehicles, such as the Chevrolet Corvette, and in most Toyota/Lexus hybrid-electric vehicles.

Gelled Electrolyte Battery

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. Gel batteries are usually not used in automotive applications but instead are used in electric wheelchairs and scooters.

Gel battery

A lead-acid battery with silica added to the electrolyte to make it leak proof and spill proof

Valve-regulated Lead-Acid batteries

Both AGM and gel batteries are called valve-regulated lead–acid (VRLA), also called sealed valve-regulated (SVR) or sealed lead–acid (SLA), batteries. These batteries use a low-pressure venting system that releases excess gas and automatically reseals if a buildup of gas is created due to overcharging. Both types of valve-regulated lead-acid batteries are also called recombinant battery design

Recombinant battery

A recombinant-type battery means that the oxygen gas generated at the positive plate travels through the 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.

Normal Life of a battery

Most automotive batteries have a useful service life of 3 to 7 years, proper care can help increase the life of a battery, but abuse can shorten it.The major cause of premature battery failure is overcharging.

Battery sulfation

During charging of a battery, the lead sulfate is converted back to lead.When a battery is left in a discharged condition, the lead sulfate re-crystallizes into hard lead sulfate.This process is called sulfation or a sulfated battery.

What most operate correctly to prevent damage to the battery?

The automotive charging circuit,consisting of an alternator and connecting wires.

What can damage the battery?

• Charging voltage higher than 15.5 volts can damage a battery by warping the plates as a result of the heat of overcharging

• AGM batteries can be damaged if charged at a voltage higher than 14.5 volts

Overcharging

Causes the active plate material to disintegrate and fall out of the supporting grid framework.Vibration or bumping can also cause internal damage similar to that caused by overcharging.It is important, therefore, to ensure that all automotive batteries are securely clamped with the battery hold-down bracket in the vehicle.The shorting of cell plates can occur without notice.If on of the six cells of a 12-volt battery is shorted, the resulting voltage of the battery is only 10 v.With only 10 V available,the started usually is not able to start the engine.

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.

Battery Vent Tubes

If a battery is installed inside a vehicle, vent tubes are used to route battery fumes to the outside so they don’t get into the passenger compartment.

What determines Battery Capacity?

The capacity of any battery is determined by the amount of active plate 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.

3 Different ways the battery can be tested?

Cold cranking amps (CCA), Cranking Amps (CA), reserve capacity.

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 ampere rating of a battery is the number of amperes that can be supplied by a battery at 0°F (−18°C) for 30 seconds while the battery still maintains a voltage of 1.2 volts per cell or higher. This means that the battery voltage is 7.2 volts for a 12-volt battery and 3.6 volts for a 6-volt battery. . Try to purchase a battery with the highest CCA for the money. See the vehicle manufacturer’s specifications for recommended battery capacity

Cranking amperes (CA)

The designation CA refers to the number of amperes that can be supplied by a battery at 32°F (0°C). This rating results in a higher number than the more stringent CCA rating.

Marine Cranking Amperes

Is similar to cranking amperes and is tested at 32 F.

What is deep cycling?

Is almostfully discharging a battery and then completely recharging it. Golf cart batteries are an example of lead–acid batteries that must be designed to be deep cycled. A golf cart must be able to cover two 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.

Reserve Capacity

The rating for batteries is the number of minutes that 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 a vehicle can be driven in the event of a charging system failure.

Ampere Hour

Is an older battery rating system that measures how many amperes of current the battery can produce over a period of time. For example, a battery that has a 50 amp-hour (A-H) rating can deliver 50 amperes for 1 hour or 1 ampere for 50 hours or any combination that equals 50 amp-hours.

(BCI) Battery Council International.

Battery sizes are standardized by the BCI. When selecting a replacement battery, check the specified group number in service information, battery application charts at parts stores, or the owner’s manual.

Typical Group size applications

• 24/24F (top terminals). Fits many Honda, Acura, Infiniti, Lexus, Nissan, and Toyota vehicles.

• 34/78 (dual terminals, both side and top posts). Fits many General Motors pickups and SUVs, as well as midsize and larger GM sedans and large Chrysler/Dodge vehicles.

• 35 (top terminals). Fits many Japanese-brand vehicles.

• 65 (top terminals). Fits most large Ford/Mercury passenger cars, trucks, and SUVs.

• 75 (side terminals). Fits some General Motors small- and midsize cars, and some Chrysler/Dodge vehicles.

• 78 (side terminals). Fits many General Motors pickups and SUVs, as well as midsize and larger GM sedans.

Battery group size application will determine

Terminal location.