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Chevrolet Equinox Service Manual: Charging System Description and Operation Starting System

Chevrolet Equinox Service Manual / Powertrain / Engine / Charging System Description and Operation Starting System

Electrical Power Management Overview

The electrical power management system is designed to monitor and control the chargingsystem and send diagnostic messages to alert the driver of possible problems withthe battery and generator. This electrical power management system primarily utilizesexisting on-board computer capability to maximize the effectiveness of the generator,to manage the load, improve battery state-of-charge and life, and minimize the system'simpact onfuel economy. The electrical power management system performs 3 functions:

It monitors the battery voltage and estimates the battery condition.It takes corrective actions by boosting idle speeds, and adjusting the regulated voltage.It performs diagnostics and driver notification.

The battery condition is estimated during ignition-off and during ignition-on. Duringignition-off the state-of-charge of the battery is determined by measuring the open-circuitvoltage. The state-of-charge is a function of the acid concentration and the internalresistance of the battery, and is estimated by reading the battery open circuit voltagewhen the battery has been at rest for several hours.

The state-of-charge can be used as a diagnostic tool to tell the customer or the dealerthe condition of the battery. Throughout ignition-on, the algorithm continuously estimatesstate-of-charge based on adjusted net amp hours, battery capacity, initial state-of-charge,and temperature.

While running, the battery degree of discharge is primarily determined by a batterycurrent sensor, which is integrated to obtain net amp hours.

In addition, the electrical power management function is designed to perform regulatedvoltage control to improve battery state-of-charge, battery life, and fuel economy.This is accomplished by using knowledge of the battery state-of-charge and temperatureto set the charging voltage to an optimum battery voltage level for recharging withoutdetriment to battery life.

The Charging System Description and Operation is divided into 3 sections. The firstsection describes the charging system components and their integration into the electricalpower management. The second section describes charging system operation. The thirdsection describes the instrument panel cluster operation of the charge indicator,driver information center messages, and voltmeter operation.

Charging System Components


The generator is a serviceable component. If there is a diagnosed failure of the generatorit must be replaced as an assembly. The engine drive belt drives the generator. Whenthe rotor is spun it induces an alternating current (AC) into the stator windings.The AC voltage is then sent through a series of diodes for rectification. The rectifiedvoltage has been converted into a direct current (DC) for use by the vehicles electricalsystemto maintain electrical loads and the battery charge. The voltage regulator integralto the generator controls the output of the generator. It is not serviceable. Thevoltage regulator controls the amount of current provided to the rotor. If the generatorhas field control circuit failure, the generator defaults to an output voltage of13.8 V.

Body Control Module (BCM)

The body control module (BCM) is a GMLAN device. It communicates with the engine controlmodule (ECM) and the instrument panel cluster for electrical power management (electricalpower management) operation. The BCM determines the output of the generator and sendsthe information to the ECM for control of the generator turn on signal circuit. Itmonitors the generator field duty cycle signal circuit information sent from the ECMfor controlof the generator. It monitors a battery current sensor, the battery positive voltagecircuit, and estimated battery temperature to determine battery state of charge. TheBCM performs idle boost.

Battery Current Sensor

The battery current sensor is a serviceable component that is connected to the negativebattery cable at the battery. The battery current sensor is a 3-wire hall effect currentsensor. The battery current sensor monitors the battery current. It directly inputsto the BCM. It creates a 5 volt pulse width modulation (PWM) signal of 128 Hz witha duty cycle of 0–100 percent. Normal duty cycle is between 5–95 percent. Between0–5 percentand 95–100 percent are for diagnostic purposes.

Engine Control Module (ECM)

When the engine is running, the generator turn-on signal is sent to the generatorfrom the ECM, turning on the regulator. The generator's voltage regulator controlscurrent to the rotor, thereby controlling the output voltage. The rotor current isproportional to the electrical pulse width supplied by the regulator. When the engineis started, the regulator senses generator rotation by detecting AC voltage at thestator through an internalwire. Once the engine is running, the regulator varies the field current by controllingthe pulse width. This regulates the generator output voltage for proper battery chargingand electrical system operation. The generator field duty terminal is connected internallyto the voltage regulator and externally to the ECM. When the voltage regulator detectsa charging system problem, it grounds this circuit to signal the ECM that a problemexists.The ECM monitors the generator field duty cycle signal circuit, and receives controldecisions based on information from the BCM.

Instrument Panel Cluster

The instrument panel cluster provides the customer notification in case a concernwith the charging system. There are 2-means of notification, a charge indicator anda driver information center message of SERVICE BATTERY CHARGING SYSTEM if equipped.

Charging System Block Diagram

P16Instrument ClusterK20Engine Control ModuleG13GeneratorM64Starter MotorC1BatteryB18Battery Current SensorK9Body Control ModuleSerial Data - GMLAN Low Speed


P16-Instrument Cluster

K20-Engine Control Module


M64-Starter Motor


B18-Battery Current Sensor

K9-Body Control Module

Charging System Operation

The purpose of the charging system is to maintain the battery charge and vehicle loads.There are 6-modes of operation and they include:

Battery Sulfation ModeCharge ModeFuel Economy ModeHead lamp ModeStart Up ModeVoltage Reduction Mode

The engine control module (ECM) controls the generator through the generator turnON signal circuit. The ECM monitors the generator performance though the generatorfield duty cycle signal circuit. The signal is a pulse width modulation (PWM) signalof 128 Hz with a duty cycle of 0–100-percent. Normal duty cycle is between 5–95 percent.Between 0–5 percent and 95–100 percent are for diagnostic purposes. The followingtable showsthe commanded duty cycle and output voltage of the generator:

Commanded Duty Cycle

Generator Output Voltage


11 V


11.56 V


12.12 V


12.68 V


13.25 V


13.81 V


14.37 V


14.94 V


15.5 V

The generator provides a feedback signal of the generator voltage output through thegenerator field duty cycle signal circuit to the ECM. This information is sent tothe body control module (BCM). The signal is PWM signal of 128 Hz with a duty cycleof 0–100 percent. Normal duty cycle is between 5–99-percent. Between 0–5 percent and100 percent are for diagnostic purposes.

Battery Sulfation Mode

The BCM will enter this mode when the interpreted generator output voltage is lessthan 13.2 V for 45 minutes. When this condition exists the BCM will enter Charge Modefor 2–3 minutes. The BCM will then determine which mode to enter depending on voltagerequirements.

Charge Mode

The BCM will enter Charge Mode when ever one of the following conditions are met.

The wipers are ON for more than 3 seconds.GMLAN (Climate Control Voltage Boost Mode Request) is true, as sensed by the HVACcontrol head. High speed cooling fan, rear defogger and HVAC high speed blower operationcan cause the BCM to enter the Charge Mode.The estimated battery temperature is less than 0°C (32°F).Battery State of Charge is less than 80 percent.Vehicle speed is greater than 145 km/h (90 mph)Current sensor fault exists.System voltage was determined to be below 12.56 V

When any one of these conditions is met, the system will set targeted generator outputvoltage to a charging voltage between 13.9–15.5-V, depending on the battery stateof charge and estimated battery temperature.

Fuel Economy Mode

The BCM will enter Fuel Economy Mode when the estimated battery temperature is atleast 0°C (32°F) but less than or equal to 80°C (176°F), the calculated battery currentis less than 15 amperes and greater than −8 amperes, and the battery state-of-chargeis greater than or equal to 80 percent. Its targeted generator output voltage is theopen circuit voltage of the battery and can be between 12.5–13.1 V. The BCM will exitthis mode andenter Charge Mode when any of the conditions described above are present.

Head lamp Mode

The BCM will enter Head lamp Mode when ever the head lamps are ON (high or low beams).Voltage will be regulated between 13.9–14.5 V.

Start Up Mode

When the engine is started the BCM sets a targeted generator output voltage of 14.5V for 30 seconds.

Voltage Reduction Mode

The BCM will enter Voltage Reduction Mode when the calculated ambient air temperatureis above 0°C (32°F). The calculated battery current is less than 1 ampere and greaterthan −7 amperes, and the generator field duty cycle is less than 99 percent. Its targetedgenerator output voltage is 12.9 V. The BCM will exit this mode once the criteriaare met for Charge Mode.

Instrument Panel Cluster Operation

Charge Indicator Operation

The instrument panel cluster illuminates the charge indicator and displays a warningmessage in the driver information center if equipped, when the one or more of thefollowing occurs:

The engine control module (ECM) detects that the generator output is less than 11V or greater than 16 V. The instrument panel cluster receives a GMLAN message fromthe ECM requesting illumination.The instrument panel cluster determines that the system voltage is less than 11 Vor greater than 16 V for more than 30-seconds. The instrument panel cluster receivesa GMLAN message from the body control module (BCM) indicating there is a system voltagerange concern.The instrument panel cluster performs the displays test at the start of each ignitioncycle. The indicator illuminates for approximately 3 seconds.


The BCM and the ECM will send a serial data message to the driver information centerfor the BATTERY NOT CHARGING SERVICE CHARGING SYSTEM or SERVICE BATTERY CHARGING SYSTEMmessage to be displayed. It is commanded ON when a charging system DTC is a currentDTC. The message is turned OFF when the conditions for clearing the DTC have beenmet.

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Electrical Power Management Description and Operation Starting System
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Finish Care
Application of aftermarket clearcoat sealant/wax materials is not recommended. If painted surfaces are damaged, see your dealer to have the damage assessed and repaired. Foreign materials such as calcium chloride and other salts, ice melting agents, road oil and tar, tree sap, bird droppings ...

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