Battery Testing & Service

Chapter 30

Battery Testing & Service

Objective: After studying this chapter, you will be able to summarize the most common methods for testing and servicing batteries.

Battery Maintenance

The five (5) primary steps in maintaining an automotive battery are:

Checking the electrolyte level Cleaning the battery terminal connections Cleaning the battery top Checking the battery hold down and tray Inspecting for physical damage to the case

and terminals

Battery Maintenance

Safety Glasses must be worn at all times

Battery Maintenance

The best solution to correctly wash an automobile battery is baking soda and water.

Battery Maintenance

A battery-terminal test1. Hold (-) lead to cable near clamp2. Hold (+) lead to negative battery post3. Disable ignition or injection system4. Crank engine while watching voltmeter

Battery Maintenance

A battery-terminal test RESULTSVoltmeter shows over .5 volts = FAILMeans high resistance is present at cable connection and cable end needs cleaning or replacement.Voltmeter shows less than .5 volts = PASS

Battery Maintenance

Preventing Terminal CorrosionCoat the connection with petroleum jelly or

white grease, this will help prevent corrosion from battery gasses.

Battery Maintenance

The automotive memory saver is designed tomaintain the memory of your on-board vehicle computer when your battery is disconnected. Not to mention the radio stations and clock!

Battery Maintenance

If the cells of a maintenance-type battery are low, the correct refill liquid is distilled water.

Battery Safety

Hydrogen gas is both colorless and odorless, but it is also extremely flammable and explosive!

Battery Testing

The density of a liquid can be checked by using a Hydrometer or Specific Gravity Tester.

Specific Gravity indicates the state of charge of the battery

Battery Testing

A battery with a specific gravity of 1.265 has a higher state of charge than a battery with a specific gravity of 1.250

Battery Testing

the battery’s condition is defective if the hydrometer readings vary 25 or more points between cells

Battery Testing

Battery Voltage Test To check the open-circuit

voltage of your battery, first disconnect the battery cables so that no power is coming in or going out. Set your multimeter to read “DC volts” (for meters without auto ranging, set the scale to 20 volts), and touch the red (positive) probe to the positive battery terminal and the black (negative) probe to the negative terminal as shown here.

Battery Testing

Battery Voltage Test RESULTS

0

10

20

30

40

50

60

70

80

90

100

11.80 12.00 12.20 12.40 12.60

Percent Charge

Battery Testing

CELL VOLTAGE TEST.—The cell voltage test will let you know if the battery is discharged or defective. Like a hydrometer cell test, if the voltage reading on one or more cells is .2 volts or more lower than the other cells, the battery must be replaced.

Battery Testing

battery drain test - looking for a parasitic drain. A parasitic drain is when an electrical device is

using battery power when the car is closed, and the ignition key removed. Therefore, when doing this test make sure that the dome light, under hood light, trunk light, etc. are off. This normally is less than 25-50 milliamps. More than that indicates a battery drain problem and should be repaired.

Battery Charging

A battery charger transforms AC voltage into DC voltage.

It is NEVER safe to charge a frozen battery because it WILL explode!

Battery Jump Starting

STEP 1: Connect one end of the Positive(+) cable to the Positive(+) post of the dead battery.

STEP 2: Connect the other end of the Positive(+) cable to the Positive(+) post of the good battery.

STEP 3: Connect one end of the Negative(-) cable to the Negative(-) post of the good battery.

STEP 4: Connect the other end of the Negative(-) cable to a good solid SHINY, NON PAINTED metal part of the engine on the dead car. Usually a giant shiny nut on the engine block will do. A painted, dirty, or oily nut will not work. You usually want to avoid placing the Negative(-) cable directly on the dead battery to minimize the chance for explosions. You should only use the ground post on the dead battery as a last resort. On this step you'll get a normal spark as you connect the ground and complete the circuit.

NOW START THE DEAD VEHICLE!

Battery Jump Starting

Remove cables in reverse orderCAUTION! If polarity is reversed when attaching

jumper cables, serious damage to the charging or computer systems can occur to either vehicle. Watch what you are doing!

Battery Jump Starting

A portable battery-pack is a safer and easier method to jump-starting a vehicle if the directions are closely followed.

Failure to follow directions can cause the same consequences as incorrect jump starting, such as explosion or damage to onboard computer systems.

Battery Load Test

A battery load test checks the battery under full current load.

Most modern load testers have inductive type ammeter connection leads.

During load testing, the automatic testers subject the battery to three times the battery’s amp-hour rating.

For Example: A 110 amp-hour battery would be loaded to 330 amps.

Modern battery’s use the S.A.E. rating of Cold-Cranking-Amps

If a 12 volt automotive battery shows 9.6 volts or more during load testing, the battery is in good condition.

More Battery Tests

A 3 minute quick test will determine if a battery is defective and no longer serviceable.

A three-minute battery charge test checks for a sulfated battery. This battery test requires charging the battery at 40 amps for three minutes, then checking the voltage across the terminals with the charger on. If the voltage is above 15.5 volts, the battery is not accepting a charge and should be replaced.

Other Battery Problems

If all the battery tests are good, some other areas to inspect for charging system problems are:

Defective charging system Battery drain Loose alternator belt Corroded, loose, or defective battery cables Defective starting system

Battery Replacement

To remove a battery, first disconnect the cables. Then loosen the battery hold-down. Using a battery strap or battery carrier, carefully lift the battery out of the vehicle. Warning! Always wear Safety Glasses!

Selecting a Replacement Battery

CCA rating must be at least equal to OEM Size of battery should fit into its tray Hold down should secure battery in place Terminals should be in correct location and

of same design as original battery.

Questions?

Refer to chapter 30 in the Duffy text.

Or see on-line:

Car Battery Myths & Facts