State Of Charge (SOC)
The hybrid vehicle control ECU assembly estimates the SOC of the HV battery from the accumulated amperage that is constantly and repeatedly being charged and discharged. In order to maintain the SOC at the appropriate level all the time, the hybrid vehicle control ECU assembly controls the hybrid system optimally.
While the vehicle is in motion, the HV battery undergoes repetitive charge/discharge cycles as it becomes discharged by motor (MG2) during acceleration and charged by regenerative braking during deceleration. The hybrid vehicle control ECU assembly calculates the SOC based on the amount of HV battery charge/discharge detected by the HV battery current sensor. The hybrid vehicle control ECU assembly constantly performs charge/discharge control based on the calculated SOC value in order to maintain the SOC within its target range.
Cooling System Control for HV Battery
The hybrid vehicle control ECU assembly receives signals from the HV battery temperature sensors and HV battery intake air temperature sensor. Then, the hybrid vehicle control ECU assembly steplessly actuates the battery cooling blower assembly using duty cycle control, in order to maintain the HV battery temperature within the specified range.
The battery voltage sensor converts the HV battery related signals (voltage, current and temperature) into digital signals, and transmits them to the hybrid vehicle control ECU assembly via serial communication. Also, the battery voltage sensor detects and transmits the blower speed feedback frequency, which is necessary to perform the cooling system control, to the hybrid vehicle control ECU assembly.
Detection of Insulation Resistance Decrease
The leak detection circuit is built into the battery voltage sensor. The leak detection circuit constantly monitors that the insulation resistance between high-voltage circuits and body ground is maintained.
The hybrid vehicle control ECU assembly determines decreases in the insulation resistance based on the information from the battery voltage sensor.
The leak detection circuit has an AC source and causes a small amount of AC to flow to the high-voltage circuit (positive and negative).
The more insulation resistance decreases, the more voltage steps down at the detection resistor and the lower the waves of AC. The insulation resistance value is detected based on the amplitude of AC waves.
Cut-off of High-Voltage Circuits during Collision
If the vehicle is involved in a collision as described below, the hybrid vehicle control ECU assembly will shut down the power supply by turning the system main relays off for safety.
The hybrid vehicle control ECU assembly receives the airbag deployment signal from the airbag sensor assembly during a frontal collision, side collision or rear collision.