Cadillac Roadside Service

Cadillac Roadside Service

Cadillac Roadside technicians (during a roadside repair) cannot test and recharge batteries. Use the following procedure when replacing a battery on a roadside visit.

Important:
Battery testing procedures should be followed after returning to the dealership.

^ The technician should take the battery back to the dealership and perform a Midtronics test, J 42000.

^ The code should be included in the comment section of the warranty claim when the claim is submitted.

^ If the battery is found to test good, note the code in the comment section of the claim followed by the verbiage BATTERY GOOD - ROADSIDE REPAIR.

Background Information

Batteries

What is a battery? The battery is a reservoir. Think of a battery as a water tower (reservoir) for your city's water system. The water tower stands some 60 feet in the air. The forces of gravity on the volume of water in the tower determines the pressure within the system.

Opening a valve in the water system allows water to flow through the pipes to the consumer. Water flowing from the tower lowers the force of gravity (pressure) on the volume of water standing in the tower. If the water is not replaced, pumped into the water tower (recharged), the water system pressure would drop. The volume of the water being released from the system determines the discharge rate.

When defining pressure in an electrical circuit, the term volts is used as compared to pounds per square inch in other systems.

A battery is made up of 6 individual cells. Each individual cell is able to store a small amount of pressure (voltage). Each individual cell has the capacity of approximately 2.1 volts (pressure). When the 6 individual cells are connected in series, you have a 12.6 volt battery. The pressure (voltage) of the battery may be measured and displayed on a digital multi meter.

A piece of stranded wire, with only one strand (which could be as small as the hair on your head) making contact with the battery source, will show either battery voltage with the engine off, or system voltage when the engine is running.

Voltage readings do not indicate the volume of (current/amperage) electrical energy available. Your diagnostic routine must determine the amount of electrical energy (amperage) available.

For example, a new AAA battery, as used in a flash light, has a voltage level of approximately 1.6 volts. If you place 8 AAA flash light batteries in series and measure them with a multi meter, the result will be a reading on the multi meter exceeding 12 volts. The question: will this 12 volts start a vehicle engine? The answer is No. Why not? The volume (amps) is not sufficient to energize the cranking motor.

Amperage/current are terms used to define the volume of electrical energy within an electrical circuit. Batteries store amperage under pressure (voltage).

Turning on a switch within an automotive electrical system allows current (amperage) to flow through the connecting wires to the consumer (the consumer in an electrical system is any motor, bulb, actuator or other device). The current (amperage) flowing from the battery reduces the voltage (pressure). If the current/amperage is not replaced by charging, battery voltage will drop.

Think of it this way. Amperage does the work; voltage is the pressure. When you touch a 110 volt AC current source at home, you get quite a shock because of the amperage available. How many of you have seen another technician or yourself feel the wallop of the ignition systems 40,000 + volts. There is very little current here, however, if the amperage were higher, the technician would suffer extreme consequences.

What does a battery green eye really mean? A green eye means the cell in which the eye is placed is more than 65% charged, however, other cells in the battery may be low on electrolyte, or a cell may be internally shorted and the battery may not perform properly. The green eye is an indicator of the state of charge of that particular cell. The green eye is an attempt, when all things in all cells are equal, to give a hydrometer indication of the one cell and apply that to the entire battery. To properly test a suspect battery, you must use the Midtronics Battery tester.

Testing the Battery with the Midtronics Micro 410 Tester, J 42000

Important:
The Midtronics Micro 410, J 42000, (tester) helps identify battery problems. However, it is NOT CAPABLE OF TESTING THE CHARGING SYSTEM (GENERATOR) OR PERFORMING PARASITIC LOAD TESTS.

The Midtronics Digital Battery Analyzer, (tester), J 42000, should be used to determine the state of health and charge level of the battery prior to any battery or generator replacement (unless physical damage is found to either the battery or the generator). The tester, J 42000, uses conductance technology instead of traditional load testing. The tester allows you to test most batteries that are partially discharged without first performing the time consuming charging and load testing procedure. The tester helps quickly identify batteries that are serviceable and just need to be re-charged. Battery testing is best performed in the vehicle at the battery terminals. If you cannot access the battery terminals, remove the battery and test the battery out of the vehicle. As with any electrical test, a good connection is very important to battery testing.

Generators

The automotive generator is a highly complex electromechanical device. Generators apply the principles of magnetic induction to automotive electrical systems to supply proper current (amperage) and voltage (pressure) regulation during all driving conditions.

Proper testing of the generator requires that the battery be at a full state of charge. The generator's voltage and ampere outputs will be controlled/regulated based on the batteries state of charge. The generator's internal voltage regulator monitors the vehicle system voltage and will control the charging system voltage output. Controlling the charging system in the range of 13.5 to 16.0 volts prevents over/under charging of the battery, depending on the generator used in the vehicle.
Generators internally produce alternating (AC) current. Before it reaches the generator's output terminal, conversion to direct (DC) current is required for automotive use.

All generators use a voltage regulator to regulate the amount of voltage (pressure) the generator maintains on the system.

All generators have a specified or designed maximum amperage (volume) rated output capacity.

A series of 6 diodes, in a rectifier system, (rectifier bridge), converts AC to DC voltage and current.

The faster a generator's rotor spins, the higher the available output of current (amperes). Generator output is directly related to engine speed (high engine speed = high available current output; low engine speed (idle) = low available current output).

Ampere output of the generator must be larger than the vehicle usage requirements or a battery discharge condition will occur.

A generator operating at engine base idle may not charge a battery unless all consumers of energy, i.e., A/C, heated seats, rear window defogger, headlights, etc. are off, and then only a small current (ampere) level may be charging the battery.

For example, a generator with a rated output of 100 amps, at 1500 engine RPM, will show the following characteristics when a diode within the rectifier bridge has a problem:

^ The generator with one failed positive diode will produce the proper regulated voltage however, only about 66 amps output.

^ If two positive diodes are defective, the generator will still produce the proper regulated voltage. However, only about 1/3 (33 amps) of rated output will be available.

^ Failed negative diodes have an effect, too, but this is generally related to shortened generator life and not to reduced output.

Consider a hypothetical example. If a vehicle requires 65 amps of current to maintain vehicle operation (i.e. radio, heater, heated seats, air conditioning, clock, memory modules, and the list goes on), at idle (650 RPM), the generator produces, say 50 amps. The balance is made up by the battery. If the generator produces 100 amps at 2000 RPM, 65 amps are used by the vehicle and the excess (35 amps), is available for recharging the battery. Over time, the generator replenishes the battery and keeps it in a fully charged state.

A customer who only drives the city streets at low speeds, especially in the winter with the headlights, heated seats, wipers, rear window defroster, and heater blower on, is discharging the battery. For a generator to produce maximum output, the engine speed must be in the 2000 RPM range or higher.

Batteries are like people in some ways. They work best when the ambient temperature is around 22°C (72°F). At a temperature of-17°C (0°F), the battery is only 60% efficient. At high ambient temperatures above 27°C (80°F), the battery wears out quicker due to the catalyst effect of temperature on the chemicals within the battery.

Battery Charging

Before charging a battery, inspect the battery for the following:

^ Inspect the battery for evidence of physical damage. If damage is found, replace the battery. If no damage is found, proceed to the next step.

^ Is the hydrometer eye clear (low electrolyte level)? If clear, tap the hydrometer lightly with the handle of a small screwdriver. Did the color change? If no, replace the battery. If yes, continue with the procedure.

Important:
If an attaching bolt is stripped, it is usually possible to clean the battery terminal threads with a thread chaser and avoid replacing the battery. The threads in the battery terminal are harder than the bolt threads, so only the attaching bolt usually needs to be replaced.

^ Inspect for loose, stripped battery cables. Attempt to rotate the battery cable end. Properly torqued battery cables will have a break-away torque requirement of 15 N.m (10 lb-ft). If the bolt is tight and the end rotates, it may be due to the following conditions:

- The attaching bolt is cross threaded.

- The attaching bolt may be too long.

- There may be foreign material lodged in the battery bolt hole.

- The battery cable end may be damaged.

- Battery cable to battery interface corrosion.

- A clear eye (low electrolyte level) rather than a green or a black eye.











Test the battery with the Midtronics tester, J 42000. The tester may detect an internal problem with the battery before time is spent charging the battery. The test procedure is shown. The test will advise the technician to charge and retest the battery when appropriate.