ALTERNATOR CONTROL




When the engine is idling, the engine-ECU or engine-A-M/T-ECU affect duty cycle control on the continuity between the alternator G terminal and the ground. (At this time, the duty cycle of the G terminal is controlled in the same way as the power transistor ON duty cycle in the voltage regulator.) When the driver turns ON the headlights while the engine is idling, the current consumption increases suddenly. However, the engine-ECU or engine-A-M/T-ECU gradually increases the OFF duty cycle of the alternator G terminal to prevent the alternator output current from increasing rapidly. Thus, the output current increases gradually. (Until the alternator generates a sufficient amount of current, the battery supplies current to the headlights.) As a result, the engine-ECU or engine-A-M/T-ECU prevents the idle speed from dropping due to a sudden increase in engine load. This control does not take place within 3 seconds after the engine has been started, even if the engine is idling. If a high signal from the alternator FR terminal is input continuously for 20 seconds or longer to the engine-ECU or engine-A-M/T-ECU while the engine is running, the engine-ECU or engine-A-M/T-ECU will determine that the alternator FR terminal circuit is open, stores DTC (Diagnostic Trouble Code) P0622 in its memory, and turns OFF the alternator G terminal.

DISCHARGE AND CHARGE CONTROL <Vehicles with AS&G system>
The engine-ECU restricts the power generation when all of the following conditions are satisfied.

  • During the vehicle running (except the speed reduction)
  • The electrical accessory loads are small.
  • After the engine starts, the battery temperature is 0°C or more.
  • The amount of battery discharge is less than the specified value.
  • The vehicle is not in the forcible full charge mode.
  • The battery deterioration judgement decides that the battery is not deteriorated.

FORCIBLE FULL CHARGE MODE
The engine-ECU is in the forcible full charge mode when the following start conditions are satisfied. During the mode, the alternator always generates the electrical power of approximately 14.4 V. When detecting that the battery is fully charged, the engine-ECU cancels the forcible full charge mode.

  • When the battery terminal is disconnected.
  • After the specified time has passed since the previous judgment on the completed full charge
  • The amount of battery discharge is more than the specified value.
  • When the battery deterioration judgement decides that the battery is deteriorated.

JUDGEMENT OF DETERIORATED BATTERY


caution The judgement of the deteriorated battery is controlled by the engine-ECU to securely operate the AS&G system. Although the judgement of the deteriorated battery decides that the battery is deteriorated, it is not necessary to replace the battery with the new one soon.
When the engine starts, the engine-ECU calculates the internal resistance of the battery by using the signal from the battery current sensor and the battery voltage. When the internal resistance of the battery is more than the specified value, the judgement of the deteriorated battery decides that battery is deteriorated.