Starting and Charging: Description and Operation

CAUTION: Before removing or installing any electrical unit or when a tool or equipment could easily come in contact with "live" exposed electrical terminals, disconnect the negative battery cable to help prevent personal injury and/or damage to the vehicle or components. Unless instructed otherwise, the ignition switch must be in the OFF or LOCK position.

CIRCUIT OPERATION:

Battery
The maintenance-free battery, which is standard on all vehicles, is completely sealed except for two small holes that allow produced gas to escape. There are no removable vent plugs in the cover.

The battery has two ratings: (1) a reserve capacity rating and (2) a cold cranking ampere rating. Reserve capacity is the time required, in minutes, for a fully charged battery at a temperature of 27°C (80°F), discharging at a constant current of 25 amperes, to reach a terminal voltage of 10.5 volts. This is an estimate of the maximum length of time a vehicle could travel with minimum electrical load and no generator output. Cold cranking amperes (CCA) is the minimum battery amperage that must be maintained for 30 seconds while meeting a minimum voltage requirement of 7.2 volts at -18°C (0°F).


Starter
The solenoid windings are energized when the ignition switch is turned to the START position. This causes the pinion to engage the engine flywheel ring gear and the solenoid main contact switch to close, which cranks the engine. When the engine starts, pinion overrun protects the armature from excessive speed until the switch is opened. Once the solenoid windings are de-energized, the return spring causes the pinion to disengage. The switch opens immediately when the engine starts to prevent excessive overrun.

Generator
The generator consists of a delta-stator, rectifier bridge, and rotor with slip rings and brushes. A conventional pulley and fan are used to cool the slip ring end frame, rectifier bridge and regulator. The voltage regulator limits the system voltage by controlling the rotor field current. While the field current is ON, the regulator switches the field current on and off at a frequency of 400 cycles per second. By varying the overall on-off time, the correct average field current for proper system voltage is obtained. At high speeds with low electrical loads, the on-time may be 10% and the off-time may be 90%. At low speeds with high electrical loads, the on-off time may be 90% and 10%,