Recently, a Cadillac car owner，Send WeChat to ask the author，Vehicle combination instrument shows the red "Battery not Charging "and" Service Charming System "fault warning light is on ( Figure 1)，Can I continue to drive。I told him that the warning information means "the battery cannot be charged，Repair and charging system "，Let him enter the store as soon as possible Repair。Because if the generator cannot charge the battery，Electric energy in the battery will soon be used with light，Spark plugs cannot ignite， The engine will soon turn off。Driving a car that can turn off at any time is very dangerous on the road。

Figure 1 Charging system fault alarm map from Cadillac car owner

Combined with the car failure phenomenon，I want to share Cadillac with you、Buick、Chevrolet and other U.S. general car series chargingControl system type, structure, principles and common fault diagnosis methods and techniques.

I. New type of regulating control system

The traditional charging system built -in temperature sensor in the car's generator，To establish a setting voltage of the generator Value。When the generator is in a cold state，The output voltage value set by the generator will increase; when the temperature seabet loginof the generator rises， Set the voltage value of the output to decrease。Car that controls the charging system with this voltage control，For a long time on the highway During the driving process，Prone to excessive charging phenomenon，But when driving at low speeds，There will be insufficient charging phenomenon。 

New type voltage adjustment control system is a new type of dynamic control vehicle system voltage system。It is mainly based on Estimated battery temperature and charging status of the battery to adjust the output voltage value of the setting generator。With fuel Economics、Extend the life of the battery、Extend the life of the bulb、The advantages of extend the life of the switch。 

GM has begun to adopt the third -generation new voltage adjustment control system ( Figure 2), mainly assembled inCaddy Lark CTS, SRX and STS ; Chevrolet andGMC Full -size trucks and a variety of SUV ; Chevrolet Cobalt and Uplander ；Buick Lacrosse and terazza ; Ponter Grand PRIX and sv6 and other new models. 

Figure 2 Buick Lacrosse Generation electrode voltage adjustment control system

New type voltage adjustment control system allows vehicle voltage to fluctuate down and down within a certain range，This fluctuation range is generally 12 ~ 14V ; and the traditional voltage adjustment device is usually Generally requires that the voltage is stable at 14V.

2. The two types of common voltage adjustment control system

At present, the common voltage adjustment on General Motors Control system includes: integrated voltage adjustment control system Unification (RVC) and Standards- Independent voltage adjustment system (SARVC). 

Integrated voltage adjustment control system (RVC) Collect the battery through the battery current sensor Charging and discharge information, and transmitted it to the body control mode block (BCM). The system accurately measures the battery positive electrode Voltage and ignition switch is in off Blocking and ignition Off is on gear ( The engine is not running) electric Road voltage. 

When the ignition switch is in off When gear, the charging status of the battery (State of Change, SOC) It is determined by accurately measure the opening voltage。Charging status is acid concentration andInternal resistance of battery17346_17351 The battery has been static and opened for several hours Reading of road voltage is estimated. 

When the ignition switch on transmission (the engine is not running)  Value), Battery capacity、Initial charging status、Temperature and other parameters continuously estimate the charging state of the battery。 

During the operation of the engine，The size of the battery discharge is mainly determined by the battery current sensor，This sensor is used to collect net AH values。

body control module (BCM) Table 1 collected by the serial data circuit The corresponding relationship between the duty duty cycle and the output voltage of the generator Various useful information related to the battery is the same as ECM/PCM Exchange information, then ECM/ PCM Direct control of the generator.

Standard- Independent voltage adjustment control system (SARVC) Not using a car Body Control Module (BCM) to achieve control. It is equipped with the battery's negative electrode cable A generator battery control module，Used to collect and analyze the current of the battery、 Voltage and battery temperature and other information。The current sensor of the battery is set in the mold inside. Generator L The duty cycle of the end is directly controlled by the engine battery control module to control it, instead of being affected by ECM/PCM Control. 

The above two voltage adjustment control systems have a correction function，so that the battery can stay in 80%for a long time Electricity status.

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Below with an integrated voltage adjustment control system (RVC) as an example, introduce voltage tone The operation mode of the control system。The basic operating mode of RVC includes: charging mode、fuel economy mode、A voltage reduction mode、Start the boost mode、front headlights/ Rear wind block Glass -based ice mode, battery vulcanization mode. RVC System 6 Seed mode is all for Let the battery be in less than 80%for a long time Electricity status，At the same time, ensure the electricity demand of automotive vehicle electrical appliances。What needs special explanation is，Not all RVC Systems will enter the above 6 operating modes. 

PCM/ECM ( generator and battery control module for full -size trucks) By the engine L Control of the circuit to control the generator，Monitor the operating state of the generator by monitoring the duty cycle signal of the magnetic field circuit of the generator。The duty occupation ratio is pulse Width signal ( Add the adjustment of pulse width)，Voltage 5V，Frequency 128Hz, Use 0~100% to indicate ( Table 1). The normal duty cycle is 5 ~ 95% Between 0 ~ 5% and 95 ~ 100% It means that the system is faulty and the diagnosis needs to be diagnosed.

1. Charging mode

Just meet any of the following conditions，The control module will be transferred to the charging mode。

● The throttle opening is more than 90%, and the amount of fuel injection ( from ECM/PCM Control spray oil) reaches 21g/s. 

● The headlights are connected to the high beam or near -light. 

● Wiper opening time exceeds 8s. 

● Electron fan of the engine radiators runs high -speed. 

● Rear window electricity heating and frosting function opens. 

● Battery charging power (SoC) Below 80%。Only satisfy any of the above items，The control module will 8 ~ 50mv/s speed Slowly increase the voltage to 13.4 ~ 15.5V ( specifically depending on the generator at that time Status).

2. fuel economy mode

Just meet the following conditions，The control module will enter the fuel economy mode。 

● The calculated environmental air temperature is higher than 0 ℃ (32 ℉ ), below or equal to 80 ℃ (176 ℉ ) ； 

● The calculated battery current is greater than 8A, but less than 15A ； 

● Battery charging power (SoC) greater than or equal to 80% ； 

● The magnetic yield signal of the generator's magnetic field is less than 99%。Under this mode，The target output voltage value of the generator is 12.5 ~ 13.1V。As long as the condition of the charging mode is met，The control module will exit this mode and enter the charging mode。 

3. A voltage reduction mode

Just meet the following conditions，The control module will enter the voltage reduction mode。 

● The calculated environmental air temperature is higher than 0 ℃ (32 ℉ ) ； 

● Calculated battery current is greater than -7A, less than 2A ； 

● The magnetic yield signal of the generator's magnetic field is less than 99% ; in this mode，The output voltage target value of the generator is 12.9V。Just satisfy the charge Conditions in the electric mode, the control module will exit this mode. 

4. Start the pressure -booster mode

When the engine starts，The control module will set the output target voltage value of the generator is 14.5V and keep 30s. 

5. The headlights/rear windshield icing mode

Just turn on the headlights ( Whether it is a near -light or a high beam)，The body control module will enter the headlight/ Rear windshield ice -based ice mode, the output voltage of the engine is 13.9 ~ 14.5V.

6. Battery vulcanization mode

The voltage of the battery is lower than 13.2V，and last 45min，Control Module Blocks will enter the battery vulcanization mode。Just enter this mode，The control module will set the output target voltage value of the generator at 13.9 ~ 15.5V Between，seabet loginand keep 5min，Subsequent，The control module decides to enter other according to the system's voltage needs mode.

Control module according to the battery status of the battery，Determined the voltage of charging。As ignition The key is in a closed state，That is during the stop of the vehicle，8H per interval，System measurement One battery voltage，Then estimate the accumulation based on the 3 voltage measured during the 24H period The battery status of the battery. If the ignition switch is on Location，is the engine operation period，The system will monitor the battery voltage in real time，and the measured value and Battery temperature for comparison，To judge the battery status of the battery，Determined to store power Pond charging current and discharge current，At the same time, control module by adjusting the charging voltage，Make it The battery has always maintained at 80% above.

​​4. System hardware 

1. Battery current -driven sensor

Battery current sensor ( Figure 3) Is a partner that can be replaced, located in power storage Near the pool，Connect with the negative electrode of the battery。The battery current sensor is 3 Hol Effect sensor，Used to monitor the current of the battery，and provide the current signal directly to Body module BCM. Body module BCM Generate 5V, 128Hz pulse occupation of the pulse Signal. When the system is normal, the duty cycle is 5%~ 95% .

Figure 3 Battery current -driven sensor

2. body control module (BCM)

body control module (BCM) Determine the output of the generator, and it is ECM/ PCM Provide information, and ECM/PCM Control the generator L 42020_42036 Monitor from ECM/PCM The magnetic field of the generator occupies the duty Signals to control the actual output power of the engine。Another，It also monitors battery electricity Stream、Positive electrode voltage、Temperature，to control the charging status of the battery。body module ( BCM) also executed or sends control instructions to ECM or other controllers to implement idling improvement and load management. 

3. The battery control module of the generator

The battery control module of the generator is a part that can be replaced，Located near the battery， and connect with the battery's negative electrode cable。It directly controls the transmission of the magnetic field control circuit of the generator Signal，Monitoring generator magnetic field duty cycle signal circuit，Monitor internal current sensor， Monitoring battery positive voltage circuit，and estimate the battery temperature，so as to decide to be electricity The charging status of the pool. Same as PCM, IPC and BCM Keep communication to achieve the voltage Regulating control function.

5. The diagnosis of the charging system

For each car，When a charging system fails，It should be charged according to this model The specific structure and specifications of the system are diagnosed，You must also check the car when encountering a fault code maintenance manual to understand the exact meaning of the fault code. 

When the charging system and the battery are faulty，The combination instrument and information display of the vehicle The screen will trigger the charging warning lights and display warning text information。The specific situation is as follows: 

● Engine control module ECM The output voltage of the generator was detected below 11V or higher than 16V，The combined instrument will receive the engine control module through GM LAN (GMLAN) The request to light up the information of the police lamp. 

● The combined instrument determines the system voltage below 11V or higher than 16V, and continue time exceeds seabet my30s，The combined instrument will receive the body control module BCM Through GM Bureau The voltage sent by the domain network exceeds the normal range of information. 

● When the ignition switch is turned on every time，The combined instrument will perform the "charging warning light" test， The charging warning light will light up 3s.

 If the charging voltage is always kept at 13.8V，instead of loading with the power system Changes and changes，This phenomenon may be that it has entered a default failure state，At this time The magnetic field control circuit of the detection generator. 

For the generator L 47595_47614 ( For example Fluke 88V -type vehicle special universal table)，You can also use an oscilloscope for Measurement。When the charging system is working normally，universal meter or oscilloscope measured ratio is 5%~95% Between，The specific value of the duty ratio depends on the mode of the charging system and Charging status of the battery. 

Integrated voltage adjustment system (RVC) The occupy ratio signal is ECM/PCM 5V generated Pulse width reference voltage signal; standard independent voltage adjustment system (SARVC) The occupy ratio signal is 5V produced by the battery control module of the generator pulse Specific reference voltage signal，This occupy ratio signal is to control the cycle by the generator itself。 

If there is a fault in the charging system，Not only should we pay attention to the failure related to the charging system code，At the same time, pay attention to the failure code related to low voltage。Because the charging system occurs When the barrier, these fault codes are first generated. 

If there is a fault in the charging system，but there is no storage fault code，then according to maintenance The operation specifications and steps on the manual detect the charging system。If you still can't find it To the fault point, you need to check the further inspection through the road trial.