CH19 charging systems STUDENT VERSION rev

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Chapter 19

Charging Systems

Charging Systems

• Primary purpose is to recharge battery

• Changes mechanical energy into electrical energy

• Voltage is induced into a wire as it passes through a magnetic field

• The voltage has positive and negative

pulses

• One pole piece

assumes north and

other south polarity

Slip Rings and Brushes

• Regulated current supplied to rotor coil via slip rings and brushes

• Most AC generators use three stator windings

Diodes with cooling fins

Rear driveshaft bearing

AC Generator Operation

• Produce alternating current

• The AC must be converted, or rectified, into direct current, DC

• The AC passes through diodes

Diodes

DC Rectification

• Using six diodes allows for full-wave

rectification

• Two diodes for each stator winding

• One diode is positive, the other negative

• The wye winding has a central neutral junction

Factors Controlling Generator Output

• Rotational speed of the rotor

• Number of windings in the rotor

• Current flow through rotor

• Number of windings in the stator

Voltage Regulation

• Output is controlled by varying current through the rotor

• Resistance in series with the field coil

• Sensing voltage allows the regulator to monitor system voltage

• Temperature also monitored

Types of Field Circuits

Types of Voltage Regulators

• Electronic regulator

– Can be internally or externally mounted

– Uses a zener diode or pulse width modulation

to control field current

• Integrated circuit voltage regulators

– Internally or externally mounted

– Controls field current through a diode trio

Types of Voltage Regulators

(cont’d)

• Computer-controlled regulation

– Is used on many late-model vehicles

– The computer (PCM) uses battery voltage and temperature to determine voltage needs

– Most systems use pulse width modulation to control field current

• Capable of high charging outputs.

• Can crank engine at high speeds

Regenerative Braking

• Braking energy used to recharge batteries

• Motor/generator converts kinetic energy into electrical energy

• A combination of conventional and

regenerative braking used

• Found on all hybrid vehicles

Preliminary Checks

• Safety Precautions

– Disconnect negative terminal

– Avoid contact with generator output terminal – Only apply pressure to front of generator

housing when applying belt tension

– Observe correct polarity of battery cables

– Keep carbon pile tester off at all times

– Use caution around moving parts

Charging Indicators

• Indicator (charge) lamp

– Operates on the principle of opposing voltages

• Meters

– Voltmeter or ammeter display on dash

• Electronic voltage monitor

– Is used to monitor voltage and control a lamp or warning message

• Inspect the battery

• Check wiring and connections

• Inspect alternator mountings for loose

or missing bolts

• Check condition of the drive belt

• Ensure proper pulley alignment

PCM-Controlled Systems

• Check DTCs

• Monitor voltage with scan tool

• PCM monitors battery current, voltage, and temperature

• May adjust idle speed to increase charging rate

Noise Diagnosis

• Noise can be mechanical or electrical

• Some electrical noise is normal

• Belts and bearings can produce noise

• Check mounting, wiring, cooling and A/C hoses and lines for misrouting

• Generator pulley should spin freely with belt removed

Regulator Tests

• Excessive charging most likely caused by voltage regulator

• Can also cause no output

• Some systems can bypass regulator for field tests

full-• Always follow manufacturer’s procedures

Voltage Output Test

• Measure battery open circuit voltage

• Run engine at fast idle (1500 rpm)

• No load voltage should be about 2 volts

higher than open circuit voltage

• If low, increase speed to 2000 rpm and turn

on accessories

• Voltage should be about 0.5 volts above

open circuit voltage

Current Output Test

• Run engine around

Circuit and Ground Resistance

• Check voltage drop of charging output

connection and ground circuit

• Test between battery positive and generator output terminal

• Test between battery negative and generator case

• Test under at least 20 amps output