VARIABLE VOLTAGE CONTROL SYSTEM
Many Nissan and Infiniti vehicles are equipped with a variable voltage control system.
In the Electronic Service Manual (ESM), section CHG-Charging System, vehicles with variable voltage control systems, which use the IPDM E/R to provided the PWM signal to the alternator, as described in this article will have a section titled POWER GENERATION VOLTAGE VARIABLE CONTROL SYSTEM and a System Diagram similar to the one above.
A Variable Voltage Control system is different in that it monitors all power usage via the battery current sensor/ This allows the ECM to control the alternator in two major ways:
- It keeps the load as low as possible to maximize fuel economy.
- It makes sure the alternator supplies enough power for all of the systems that are operating.
System Components and Operation
1. IC voltage regulator (built into the alternator)
- Regulates the voltage output of the alternator within the specifications for a given vehicle.
- The variable voltage control system supplies a Pulse Width Modulation (PWM) command signal to the IC voltage regulator to control power generation.
- If the IC voltage regulator does not receive a PWM signal, it will regulate power generation based on the design specification of the IC voltage regulator.
For example: The 2016 Maxima variable voltage control will regulate voltage output between 11.6 and 15.6 volts.
For example: On the 2016 Maxima, if the variable voltage control is not active (no PWM signal), the IC voltage regulator will control voltage output between 14.1 and 14.7 volts.
2. Battery current sensor
- The battery current sensor is installed to the battery cable at the negative terminal. It detects the charging/discharging current of the battery and sends a voltage signal to the ECM.
- Some vehicles have a battery current sensor that is a separate part from the negative battery cable, while others have a battery current sensor that is integral with the negative battery cable.
3. Electronic Control Module (ECM)
- The ECM uses signals from the battery current sensor to judge whether or not to perform power generation using variable voltage control.
- If the ECM determines that variable voltage control is needed, the ECM calculates the power needed, based on the signal from the current sensor, and sends that power generation command signal to the IPDM E/R.
4. Intelligent Power Distribution Module in Engine Room (IPDM E/R)
- The IPDM E/R converts the ECM power generation command signal into a PWM signal and sends it to the IC voltage regulator.
Accessory Installation
If an electrical accessory is grounded directly to the negative battery post:
- Its power usage will bypass the battery current sensor.
- The ECM will not receive an accurate power usage signal.
- The battery may not charge completely.
- If electrical accessories are added to the vehicle, they need to be grounded to a suitable body ground such as the frame or engine block, NOT the negative battery post.
Note:
CONSULT-III plus can monitor the variable voltage control system output and perfrom active tests on most vehicles that are equipped with varible voltage control. Refer to the Electronic Service Manual (ESM) for specific vehicles to determine which CONSULT-III plus functions are available.