Batteries Basics

8/9/2019 Batteries Basics

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Safety first

Batteries are Potential Bombs

Never test batteries without wearing wraparound safety glasses and protecting your skin from battery

acid. Battery acid is extremely caustic. It can burn you and blind you.

Always keep a first aid kit and eye wash solution handy at all times. If eye wash solution is not

available, flush any battery acid that enters the eye(s) with clean water or any drinkable liquid. Do so

immediately! Second are precious.

Never smoke near a battery. Batteries give off explosive gasses, especially when charging.

Turn off a battery charger before disconnecting the charger clamps from the battery posts. If the

charger is still on when you remove the clamps, you may create a spark that ignites the battery gases.

Never pound on a battery. It is a battery, not an anvil.

Do not add electrolyte to a battery after it is in service. If the acid level in a removable cap battery is

low, add only clean water. Do not overfill the cells Never charge a frozen battery. It may explode

Properly dispose of batteries and battery acid. Batteries are among the most recycled of all products.

Battery contents and acid pose significant health hazards, and environmentally harmful, and must be

disposed of according to federal, state, and local regulations. Failure to do so is illegal, dangerous,

and just plain stupid.


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What is Hydrometer

1.If the battery has been charged within thelast four hours, remove the Surface Charge.If the battery has been discharged within thelast 15 minutes, wait for at least 15 minutesbefore testing it.

1.While holding a clean hydrometervertically and wearing glasses,

squeeze the rubber bulb, insert thenozzle into the electrolyte in the cell,and release the bulb. The electrolytewill be sucked up into the barrel orcontainer allowing the float to ridefreely. Start with the cell that isclosest to the POSITIVE (+) terminal.2.Squeeze the rubber bulb to releasethe electrolyte back into the battery'scell.

3.To increase the accuracy of themeasurement, in the same cell,repeat this process several times sothe float will reach the sametemperature as the electrolyte.


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First Aid Tips

Check your eye wash station and first aid kit

before you need them.

Make sure your first aid supplies and eyewashare fresh and ready to go in an instant.

If eye wash solution is not available, flush any

battery acid that enters the eye(s) with clean

water or any drinkable liquid. Do so

immediately! Seconds are precious.


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How to check the batteries

Can you pleasetell the name of

this instrument, isit the load tester?And where can Iget one of this?

. What you needto get is a batteryhydrometer. Thiswill measure thestate of batterycharge. You canget them just

about anywhere,parts stores, Wal-Mart, Sears, etc.


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Why Good Batteries Go Dead

In a modern, computer-controlled vehicle, the SLI battery works sevendays a week, 24 hours a day. Keep Alive Memory (KAM) in vehiclecomputers must be powered constantly, even when the vehicle isturned off and parked. Otherwise, the vehicle computer loses all datastored in memory and must either re-learn new data, or bereprogrammed. (Maybe we should change the car battery designation

from SLI to SLIM for Starting, Lighting, Ignition and Memory!) The vehicle manufacturer may or may not publish and acceptable

standard for maximum key-off battery drain: expect the exact key-offdrain to vary by make, model, year and optional equipment.

We cannot give you a generally acceptable range for key-off battery

drain. The range is too large and varies greatly, depending on thevehicle make, model, year and accessories. One OEM mayrecommend a maximum key-off battery drain of 30 mA, while anothermay allow a maximum acceptable drain that is two or even three timesgreater. You must check the recommended battery drain specificationfor the vehicle and follow any manufacturer recommended test

procedure to ensure test accuracy.


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What's Inside the Battery?

The common 12 volt Starting-Lighting-Ignition (SLI) batteryused in cars and trucks is made of six individual cells: each cell

produces approximately 2.1 volts. Cells are connected in series,like dry cell batteries stacked end to end in a flashlight. Whenfully charged, the cells have combined voltage potential of 12.6volts measured across the battery posts.

Each cell is made of alternating positive and negative plates,

separated from one another by insulating envelopes. Theenvelopes prevent short circuits from direct physical contact

between the plates.

Each cell typically contains 12 plates (six positive and sixnegative), although the number of plates varies by battery costand design. Alternating positive and negative plates arestacked inside each cell and immersed in electrolyte (amixture of water and sulfuric acid). To save space, plates may

be placed close together, but must be physically separated andinsulated from one another to prevent a short circuit.

Cells are connected in series. This explains why six cells, each

with a voltage of 2.11 volts, combine to produce a total opencircuit battery voltage of 12.66 volts in a fully charged battery.

Plates in each cell are connected in parallel. This explains whythe number of plates has no effect on cell voltage. Adding plateswithin a cell increases battery capacity, but does not increase ordecrease battery open circuit voltage. (Open circuit voltage is

battery voltage measured across the posts with no loadsconnected to the battery.)


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Things to Remember About

Batteries Batteries must provide power: both voltage and current. Power is measured as wattage (volts times

amps equals watts).

The batterys toughest single task is operating the starter.

Battery State of Charge in low maintenance batteries with removable caps can be determined bymeasuring the Specific Gravity of the battery electrolyte using a hydrometer or refractometer.

Specific Gravity Readings will not detect a shorted or open battery.

Specific Gravity Readings in all battery cells must be within 50 points of one another.

Uniformly low specific gravity readings do not necessarily indicate a bad battery. Specific Gravity readings must be adjusted when battery temperature is 10 or more degrees F above

or below 70 degrees F.

Battery State of Charge in sealed top batteries can be determined by measuring the battery OpenCircuit Voltage (voltage across the battery posts) using an accurate digital multimeter.

Battery Rating systems are used to indicate how much cold cranking current a battery can provide ofhow long the battery can provide a specified amount of current without a recharge.

A Load Test measures a batterys stamina: battery stamina is its ability to provide current whilemaintaining adequate voltage.

A battery should be at 75% State of Chargeor higherbefore a load test is performed.

A slow charge is better for the battery than a fast charge.

Normal vehicles consume small amounts of electrical current at all times to maintain memoryfunctions known as Keep Alive Memory (KAM). KAM is lost if all power is removed from thecomputer.

Key-off battery drain can discharge a good battery by consuming currents after the vehicle is shut

down.


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The Load Test

What Is a Load Test?

A Load Test is exactly what the name suggests! A measured electrical load is applied to the battery

for a specific time using a device called a Load Tester.

Load Testers

The Load Tester is commonly referred to as a Volt-Amp Tester, or VAT for short. Its main

components include:

A voltmeter connected to the battery terminals by large cables and clamps

An ammeter, connected around either the VAT main cables with an inductive current clamp, also

referred to as an amp probe.

An adjustable carbon pile inside the load tester that creates an electrical load. The amount of load

applied to the battery is adjusted with a knob on the front of the load tester.

What is a Load? A Load is any electrical consumer. During normal vehicle operation, many types of load consume

electrical power. Examples of loads include: the starter, headlights, ignition system, fuel pump,

comfort and convenience items, and heater blower. Even the vehicle computer is a load.


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Testing State of Charge in

Sealed Batteries

Testing State of Charge in Sealed Batteries

The Open Circuit Voltage Test

If the battery has a sealed top, you cannot perform aspecific gravity test to determine the battery state ofcharge since there is no way to take samples of theelectrolyte.

To determine battery state of charge in sealed-topbatteries, you must perform an Open Circuit Voltagetest across the battery posts using an accurate digitalvoltmeter; analog voltmeters are not accurate enoughfor this test. Open Circuit Voltage (OCV) refers tovoltage measured across the battery posts with noelectrical loads turned on.

Adjust your digital multimeter to the 20 or 40 VoltSC scale and place the meter leads across the battery

posts.

Take the voltage reading and compare it to the chartto the right. The chart combines specific gravity andOCV test standards.

There is a direct relationship between specificgravity and open-circuit voltage measured across the

battery posts. Batteries below 75% of full chargemust be recharged before performing a load test.


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Testing for Key-Off Battery Drain with a One-Ohm Resistor and

Voltmeter

Another accurate way to measure key-offbattery drain is to connect a one ohm-10watt

resistor in series between the disconnectednegative battery cable and negative batterypost. Then measure the voltage droppedacross the resistor. Voltage displayed on themeter will equal the current draw in amp.(Millivolt reading will equal the current drawin milliamps.) And, since the meter is set tovolt DC and is connected in parallel to theresistor, there is no danger to the meter fuse.

Ohms law makes this work, since we knowthat it takes one volt to push one amp throughone ohm of resistance. Each unit (amp ormilliamp) of current drops the same amountof voltage (amp or milivoltage) pf currentdrops the same amount of voltage (ormillivoltage) through a one ohm resistor.

Make an inexpensive tester by installing aone ohm resistor in a small plastic projectbox, available from an electronics supplystore. Add two banana jack receptacles andtest leads with clamps. Solder the connectionsinside the box as shown. To use the tester,clamp it between the negative cable end: theninsert the voltmeter meter leads into the

banana jacks. If the meter displays 10mV, thedraw is 10mA.


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Temperature Correction

If the temperature of the electrolyte isbelow 80 degrees F, subtract .004 (4points) from the actual reading for each10 degree change.

Add 4 points for each 10 degree change

above 80 degrees F.

For example, if the actual specificgravity reading is 1.265, but theelectrolyte temperature is only 30degrees F, then the true, correctedspecific gravity is 1.245 (1.265-.020 =1.245).

Why? Because the higher 1.265 specificgravity reading at 30 degrees F is theresult of the increased density of colderelectrolyte, not because the samplecontains a higher concentration of acid.


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Performing the Load Test

Part One

Important Notes:

Rotate the load tester knob to apply the correct loadas quickly as possible. This ensures accurate testresults.

Measure the battery voltage at exactly 15 seconds,once again to ensure an accurate battery evaluation.

Do not apply of a CA rating. Use only the CCArating.

Evaluating the Load Test

Battery voltage should be at least 9.6 volts at the endof the 15 second load test with battery temperature at70 degrees F. Slightly lower voltage values arenormal when temperatures are below 70 degrees F.Refer to the chart to the right to make the correctionsfor battery voltage minimums when battery

temperature is below 70 degrees F. Batteries that barely fail when tested at 75% maypass when fully charged. (For example, the batteryvoltage drops to 9.4 volts.) Recharge to 100% andretest.

Batteries that pass with room to spare when tested at75% have a better than average reserve capacity. (Forexample, battery voltage is 9.8 volts at the end of theload test.)


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Key-Off Battery Drain:

Definition & Testing

What is a Key-Off Battery Drain?

If youve ever left your headlights on in a parking lot and returned later to find your car

has a dead battery, you know what a key-off battery drain is: Key-off battery drain is any

load that continues to consume electrical power after the vehicle ignition is switched

off. We sometimes refer to a key-off battery drain as a parasitic draw, since theunwanted electrical load draws the life from the battery. On the previous pages, we have

introduced KAM, a normal key-off battery drain that does not normally result in a dead

battery. Common key-off battery drains required to power KAM fall in a 10-60

milliamp range. Check the specification to be sure.

Not so normal key-off drains that will kill a battery include glove box and trunk lights

that continue to burn out of sight due to a damaged or improperly adjusted light

switch. Others include a B+ voltage wire that shorts to ground or a faulty

microprocessor that does not power down to sleep mode, where it consumes only

enough power to maintain KAM. Unlike KAM, some key-off loads may consume

several amps (not milliamps) as they continue to operate. Obviously, the more current

consumer by a key-off drain, the faster the battery dies.


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Jump Starting Procedure -II

1. Connect the red jumper cable

clamp to the positive post of the

dead battery.

2. Connect the other red cable

clamp to the positive post of the

jumper battery.

3. Connect the black jumper

cable to the negative post of

the good battery.

4. Connect the remaining blackjumper cable clamp to bright

metal on the engine of the

vehicle with the dead battery.


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Jump Starting Procedure -I

Jump Starting Procedure

Before you begin connecting jumper cables:

Make sure the dead battery is not frozen. Do not attempt to jump start a frozen

battery. It could explode.

Ensure that both batteries are the same voltage. A 24 volt jump start of a 12 volt systemcan damage vehicle electronics.

Park the cars close enough to connect the jumper cables, but not touching.

Place the cars in Park of Neutral and set the parking brake. Never stand between the

vehicles when they are parked nose to nose.

Turn off the ignition switch and all accessories in both vehicles.

Set the hand/foot brake in both vehicles.


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Dual Battery Systems

Dual Battery Systems

Some vehicles are equipped with dual batteries. Thisis particularly true in heavy duty applications thatrequire additional power to operate the startermotor. Dual batteries may be connected in series todouble the voltage available to the starter. They mayalso be connected in parallel to provide morecranking current at 12 volts.

In a series battery connection, the batteries areconnected in line: the negative and positive terminalsalternate. While 24 volts are available for the starter,normal 12 volt accessories (lights, wipers, etc.) areconnected to one of the dual batteries.

A series battery connection is similar to the batteryconnection in a flashlight, where batteries arestacked. In a series connection, the total voltage isequal to the sum of the battery voltages.

To provide additional current for a 12 volt starter in aheavy duty application, dual batteries may beconnected in parallel. Some heavy duty applicationsrequire 1800 CCA or more at 12 volts.

This is common in vehicles with large displacementengines.

Here is the connection required to perform a 24 voltjump start. Do not connect a 24 volt jumper batteryto a 12 volt system or you will damage 12 volt loads,especially solid state components.


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Charging Rates

Reserve Capacity Slow Charge Fast Charge

80 min or less 15 hours @ 3 amps 5 hours @ 3 amps

80-125 min 21 hours @ 4 amps 7.5 hours @ 4amps

125-170 min 22 hours @ 5 amps 10 hours @ 5amps

170-250 min 23 hours @ 6 amps 7.5 hours @ 20

amps

More than 250 min 24 hours @ 10 amps 6 hours @ 40amps


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Battery Charging Overview There are two things needed to charge a battery: a voltage source strong enough to

move current through the batteryand time. The time required to charge a batterydepends in part on battery state of charge when the charging begins.

The more current we can push into the battery, the faster we can charge it.Unfortunately, faster is not always better when it comes to battery charging. Charging attoo high a rate can overheat and damage the battery.

When in doubt, charge at a slow rate. This reduces stress on the battery and chancesof plate damage caused by overheating.

The time needed to recharge a battery also depends on the battery state of chargewhen charging begins. At a given charging rate, a totally discharged battery takes morethan twice as long to recharge than one that is half-discharged. Why? Electrolyte in thetotally discharged battery contains much more water than acid, and water is a poorerelectrical conductor than acid. As water changes back to acid during the initial charge,the conductivity of the electrolyte increases, but this takes additional charge time.

Low temperatures slow chemical reactions. Cold batteries take longer to charge than

warm ones.Check battery temperature periodically during charging. If the batterycase is hot to the t ouch (125 degrees F or more) stop charging immediately until thebattery cools. Resume charging at a lower rate to prevent battery overheating. If theelectrolyte bubbles, cut back the charge rate immediately. Bubbling indicatesovercharging.


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Battery Rating Systems

Battery Rating Systems

There are several battery rating systems used: well concentrate of the three youll see most often.These rating systems are designed to tell us how much power the battery was designed to deliverwhen new and fully charged.

Here are the common ratings:

Cold Cranking Amps rates the batters ability to deliver amperage for 30 second at 0 degree F whilemaintaining a post voltage of 7.2 volts (1.2V/cell). For example, an 800 CCA battery can deliver 800amps for 30 seconds at 0 degree F and still have 7.2 volts, measured across its posts. This is a veryimportant standard for vehicles in cold climates. CCA tells us how well we can expect a battery tocrank the engine in cold weather.

Cranking Amps is a less strenuous measurement of the batterys cranking power. The CA rating isthe current (in amps) that a battery can deliver for 30 seconds at 32 degrees F while maintaining aminimum voltage of 7.2 volts (1.2V/cell). This is not to be confused with CCA, especially when

choosing a battery for use in cold climates. Sometimes referred to as Marine Cranking Amps (MCA). Reserve Capacity (RC) measures the batterys ability to provide sustained current. This rating is

important for batteries installed in vehicles with high key-off battery drains. Reserve Capacity is thetime (in minutes) required for a steady 25 amp draw to pull battery voltage below 10.5 volts at 80degrees F. RC is an important consideration for vehicles that are frequently driven for short distancesin stop-and-go traffic or those with high key-off loads.


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Battery Short Circuits

Battery Short Circuits

A common cause for sudden and unexpected battery failure is a

shorted cell. A vehicle may start and run perfectly prior to the failure,

but fail to restart only minutes after the engine is shut off. As batteries age, plate material falls off and settles to the bottom of the

battery case. This mud accumulates until it eventually bridges the

narrow gap between the plates, creating a short circuit. Simple math

tells us that total battery voltage across the posts will fall from 12.6 to

10.5 volts when an individual cell short circuits. Plates can also come in contact with one another when temperature

extremes cause plates to buckle. Freezing or extreme heat distorts

plates and damage plate material.


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Battery State of Charge -

Hydrometers Gravity and State of Charge in batteries with removable caps. Heres how:

Remove the battery caps. Check the electrolyte level. Make sure all cells are

covered but not overfilled.

Insert the hydrometer into each cell and draw electrolyte into the glass cylinder

with the squeeze ball. Draw just enough acid into the cylinder to make the

float rise. Hold the hydrometer vertical as each sample is drawn. Note the

exact level at which the fluid level intersects the measurement scale on the

float and record it.

Repeat the test at each of the remaining cells. Record the reading for each cell.

Compare readings to the chart on this page to determine state of charge. If the battery is below 75 percent state of charge, recharge it before load

testing.


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Battery State of Charge: Tools

& Testing

We can use a hydrometer to test SpecificGravity and State of Charge in batteries withremovable caps. Heres how:

Remove the battery caps. Check theelectrolyte level. Make sure all cells arecovered but not overfilled.

Insert the hydrometer into each cell and drawelectrolyte into the glass cylinder with thesqueeze ball. Draw just enough acid into thecylinder to make the float rise. Hold thehydrometer vertical as each sample is drawn.Note the exact level at which the fluid levelintersects the measurement scale on the floatand record it.

Repeat the test at each of the remaining cells.Record the reading for each cell. Comparereadings to the chart on this page todetermine state of charge.

If the battery is below 75 percent state ofcharge, recharge it before load testing


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What State of Charge Can Tell

Us State of Charge tells us if the battery is sufficiently charged to undergo

load testing. It does not tell us if the battery can deliver both voltage

and current at the same time. Thats what the load test is for. Once it is

determined that the battery state of charge is 75% or greater, the load

test measures the batterys ability to provide POWER. Power is

measured as wattage, or volts multiplied by amps.

As batteries age and deteriorate, call material degrades or falls off and

plates become less powerful. A battery that passes the specific gravity

or open-circuit voltage tests may still have a hard time maintaining its

voltage when electrical loads consume large amounts of current.


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Visual InspectionsCheck for:

Loose/corroded battery terminals. Replace temporary terminal ends with permanentcable ends.

Replace batteries that have loose posts.

Replace broken or damaged cables.

Replace batteries with severely bloated, cracked, or leaking cases.

Plan on replacing frozen batteries. Few frozen batteries survive.

Replace missing battery caps.

Add clean water to cells that are low on electrolyte in removable cap batteries. Ruleof thumb: cover the cells with inch of water. Do not overfill the cells, especiallyin a cold battery: the electrolyte level will rise when battery temperature increases,never add electrolyte to a battery already in service. Recharge the battery if

necessary.

Replace a sealed top battery that has one or more cells with a low electrolyte level.Some sealed tops have translucent battery cases that allow you to see the electrolytelevel. Never attempt to open a sealed top or alter the case by drilling or cutting.

Repair, replace, or tighten loose or damaged battery hold downs. This is a veryimportant and often overlooked aspect of battery service. A loose battery is more

apt to sustain internal damage from vibration and impact than on that is properlysecured to the battery tray

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Batteries Basics