SUB BATTERY SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Sub-battery Module Assembly Sub-battery

    • Supplies power to the electronic shift lever system during a power source malfunction.

    • Supplies power when electrical load is high.
    Sub-battery ECU

    • Detects the sub-battery voltage, battery voltage and current, and backup relay temperature.

    • Calculates the State Of Charge (SOC) of the sub-battery.

    • Controls the protection relay.

    • Sends backup relay open/close signals to the backup relay ECU.
    Protection Relay (Semiconductor Relay)

    • Opens and closes the power source circuit of the sub-battery.
    Backup Relay Backup Relay ECU

    • Controls the backup relay.

    • Detects the battery voltage and current and the backup relay temperature.
    Backup Relay (Semiconductor Relay)

    • Opens and closes the power source circuit between the battery and sub-battery.
    Shift Control ECU

    • Detects the battery voltage.

    • Requests that the sub-battery supplies the sub-battery ECU with power.

  2. SYSTEM CONTROL


    1. The protection relay and backup relay are turned on and off according to the vehicle condition.

      Situation Protection Relay Backup Relay
      When Cranking Engine On On
      During Normal Driving On On
      During a Power Source Malfunction On Off
      When in Sub-battery Protection and Deterioration Suppression Mode On Off

      Tech Tips

      When the engine switch (push start switch) is off or on (ACC), the protection relay and backup relay are turned off.


      1. When Cranking Engine


        • When cranking the engine, the battery voltage drops a large amount. Therefore, power is supplied from the sub-battery to the electronic shift lever system to stabilize the power supply voltage to the electronic shift lever system.

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      2. During Normal Driving


        • The protection relay and backup relay are turned on.

        • The sub-battery supplies power to each electric load or charges according to the electric load status.


          1. When Electric Load is High


            • The battery and sub-battery both supply power to achieve a stable power supply.

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          2. When Electric Load is Low


            • The sub-battery is charged.

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        Tech Tips

        During idling stop by idling stop control, the backup relay is turned off.

      3. During a Power Source Malfunction


        • The shift control ECU, backup relay ECU and sub-battery ECU each detect the power source voltage. When the power source voltage is less than a specified value, each ECU judges that there is a power source malfunction judgment.

        • When the sub-battery ECU judges a power source malfunction, the backup relay ECU turns the backup relay off to supply power to the electronic shift lever system.

        • Each ECU individually monitors the voltage to ensure that power source malfunctions are detected, even when a power source malfunction is only judged in the shift control ECU or backup relay ECU system.

          ECU which Judged Power Source Malfunction Operation
          Shift Control ECU The shift control ECU sends a backup request signal to the sub-battery ECU. When the sub-battery ECU receives the signal, the sub-battery ECU sends a backup relay off command to the backup relay ECU, and then the backup relay ECU turns the backup relay off.
          Sub-battery ECU The sub-battery ECU sends a backup relay off command to the backup relay ECU, and the backup relay ECU turns the backup relay off.
          Backup Relay ECU The backup relay ECU sends a power source malfunction judgment signal to the sub-battery ECU. When the sub-battery ECU receives the signal, the sub-battery ECU sends a backup relay off command to the backup relay ECU, and then the backup relay ECU turns the backup relay off.
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      4. When in Sub-battery Protection and Deterioration Suppression Mode


        • The system enters sub-battery protection and deterioration suppression mode, which suppresses the charge and discharge current to protect the sub-battery and suppress the deterioration of the sub-battery, according to the sub-battery condition. At this time, the protection relay is turned on and the backup relay is turned off.


          • Sub-battery protection and deterioration suppression mode is entered when any of the following conditions is met.


            • Overvoltage malfunction occurs in sub-battery

            • Undervoltage malfunction occurs in sub-battery

            • Sub-battery SOC is high

            • Sub-battery SOC is low

            • Vehicle voltage is low

            • Sub-battery temperature is high

            • Sub-battery may overcharge

            • Sub-battery temperature is medium to high

            • Sub-battery may overdischarge

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              Tech Tips


              • Even when the system is in sub-battery protection and deterioration suppression mode, the backup relay may be turned on depending on the vehicle condition (such as when the electric power steering is operated).

              • When the sub-battery system is malfunctioning, the protection relay and backup relay may both turn off.