HYBRID BATTERY SYSTEM


  1. SYSTEM CONTROL


    1. State Of Charge (SOC)


      1. The hybrid vehicle control ECU assembly calculates the State Of Charge (SOC) of the HV battery by estimating its charging and discharging amperages, in order to control the SOC. This allows the hybrid system to make control decisions based on the power stored in the battery..

      2. 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.

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    2. Cooling System Control for HV Battery


      1. The hybrid vehicle control ECU assembly detects increases in battery temperature via the 6 temperature sensors in the HV battery. Then, the hybrid vehicle control ECU steplessly actuates the battery cooling blower assemblies using duty cycle control, inorder to maintain the temperature of the HV battery within the specified range.

      2. While the air conditioning system is operating and cooling down the cabin, and if there is anyleeway in the HV battery temperature, the hybrid vehicle control ECU assembly turns the battery cooling blower assemblies off or sets them to a low speed. The purpose of this control is to give priority to cooling down the cabin. If this control was not performed, air takenfrom the cabin for battery cooling would slow the cooling of the cabin by the air conditioning system.

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    3. Detection of Insulation Resistance Decrease


      1. 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.

      2. The hybrid vehicle control ECU assembly determines decreases in the insulation resistance based on the information from the battery voltage sensor.

      3. 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).

      4. 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.

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    4. Cut-off of High-Voltage Circuits during Collision


      1. 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.

      2. 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.

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