HIGH VOLTAGE BATTERY CONTROL SYSTEM

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BECM

Outline

• The BECM monitors the status of the high voltage battery.

• The following sensor information is input to the BECM.

― High voltage battery cell voltage sensor

― High voltage battery module temperature sensor

― High voltage battery current sensor

― Refrigerant pressure sensor No.2

― Temperature sensor of refrigerant line for the high voltage battery

― QBC (Quick Battery Charge) voltage sensor

Functions

• The BECM has the following functions/controls.

Function

Content

High voltage battery voltage detection

•  Detects the voltage value of each high voltage battery cell (96 cells).

High voltage battery electrical current detection

•  Detects the electrical current value of the high voltage battery.

High voltage battery temperature detection

•  Detects the temperature of each high voltage battery module (16 modules).

High voltage battery electrical leakage detection

•  Detects the insulation resistance of the high voltage battery voltage and electrical leakage.

Cell balancing control

•  Equalizes the charge amount of each high voltage battery cell.

•  If the fluctuation in the charge amount of the specified value or more occurs in cell voltage, cell balancing control is performed by the BECM.

•  Monitors the state of charge of each cell and reduces the charge amount in cells with a high charge to equalize the charge amount.

SOC/SOH/SOF estimation

•  Estimates SOC (charging capacity) / SOH (deterioration condition) / SOF (discharge performance).

Power supply voltage detection

•  Monitors the power supply voltage input to the BECM.

On-board diagnostic function

•  Communicates with each sensor input to the BECM, and performs malfunction diagnosis.

CAN communication function

•  The high voltage battery condition is sent to each control module via CAN communication.

Battery heater contactor drive

•  Turns the battery heater contactor on/off.

PCM operation

•  Operates the PCM by supplying power to the PCM from the BECM.

QBC voltage detection

•  Detects the charge voltage during quick charge.

Refrigerant temperature detection

•  Detects the high voltage battery cooling refrigerant temperature.

Refrigerant pressure detection

•  Detects the high voltage battery cooling refrigerant pressure.

Electric expansion valve drive

•  Sends a drive signal to the electric expansion valve for cooling the high voltage battery, and drives the electric expansion valve.

Function	Content
High voltage battery voltage detection	• Detects the voltage value of each high voltage battery cell (96 cells).
High voltage battery electrical current detection	• Detects the electrical current value of the high voltage battery.
High voltage battery temperature detection	• Detects the temperature of each high voltage battery module (16 modules).
High voltage battery electrical leakage detection	• Detects the insulation resistance of the high voltage battery voltage and electrical leakage.
Cell balancing control	• Equalizes the charge amount of each high voltage battery cell. • If the fluctuation in the charge amount of the specified value or more occurs in cell voltage, cell balancing control is performed by the BECM. • Monitors the state of charge of each cell and reduces the charge amount in cells with a high charge to equalize the charge amount.
SOC/SOH/SOF estimation	• Estimates SOC (charging capacity) / SOH (deterioration condition) / SOF (discharge performance).
Power supply voltage detection	• Monitors the power supply voltage input to the BECM.
On-board diagnostic function	• Communicates with each sensor input to the BECM, and performs malfunction diagnosis.
CAN communication function	• The high voltage battery condition is sent to each control module via CAN communication.
Battery heater contactor drive	• Turns the battery heater contactor on/off.
PCM operation	• Operates the PCM by supplying power to the PCM from the BECM.
QBC voltage detection	• Detects the charge voltage during quick charge.
Refrigerant temperature detection	• Detects the high voltage battery cooling refrigerant temperature.
Refrigerant pressure detection	• Detects the high voltage battery cooling refrigerant pressure.
Electric expansion valve drive	• Sends a drive signal to the electric expansion valve for cooling the high voltage battery, and drives the electric expansion valve.

Construction

• The BECM is located on the left rear side inside the high voltage battery pack.

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High voltage battery cell voltage sensor

Purpose, Function

• Detects the voltage of each cell of the high voltage battery.

• Input the detected voltages to the BECM.

• Based on the detected values, calculations such as SOC (charging capacity) / SOH (deterioration condition) / SOF (discharging performance) and cell balancing control are performed.

Construction

• The high voltage battery cell voltage sensor is installed in the BECM.

High voltage battery module temperature sensor

Purpose, Function

• Detects the temperature of each module of the high voltage battery.

• Input the detected voltages to the BECM.

• Operates/stops the high voltage battery cooling system or high voltage battery heater system based on the detected value.

• The detected value is used to calculate the SOC (charging capacity)/SOH (deterioration condition)/SOF (discharge performance).

Construction

• The high voltage battery module temperature sensor detects the temperature of each module (16).

High voltage battery current sensor

Purpose, Function

• Detects the high voltage battery electrical current.

• Inputs the detected electrical current to the BECM.

Construction

• The high voltage battery current sensor is installed inside junction box No.1.

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Refrigerant pressure sensor No.2

Purpose, Function

• Detects the pressure of the high voltage battery cooling refrigerant.

• Inputs the detected electrical value to the BECM.

Construction

• The high voltage battery cooling refrigerant pressure sensor is located at the refrigerant tube outlet in the high voltage battery.

• A capacitance type high voltage refrigerant pressure sensor No.2 has been adopted to the pressure detecting part.

• The refrigerant pressure sensor No.2 consists of a pressure detecting part and signal processing part.

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Operation

• Pressure is applied to the ceramic diaphragm of the pressure detecting part according to the refrigerant pressure in the pipe.

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• A signal which changes according to the refrigerant pressure is input to the BECM.

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Temperature sensor of refrigerant line for the high voltage battery

Purpose, Function

• Measures the temperature of the high voltage battery cooling refrigerant.

• The measured value is input to the BECM.

Construction

• The temperature sensor of refrigerant line for the high voltage battery is located on the high voltage battery cooling pipe outlet side.

Operation

• Sends a signal which changes according to the cooling refrigerant temperature to the BECM.

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QBC (Quick Battery Charge) Voltage Sensor

Purpose, Function

• The QBC voltage sensor detects the charge voltage during quick charge.

Construction

• The QBC voltage sensor is located behind the high voltage battery.

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CELL BANCING CONTROL

Outline

• Lithium-ion batteries can generate heat and ignite if charged above the upper limit or discharged below the lower limit. Therefore, the BECM stops the charging when any of the cells in the high voltage battery reaches the charging upper limit, and it stops the discharging when the discharging lower limit is reached.

• While charging, if there is a large variation in the cells of the high voltage battery, the BECM will stop the charging when the cells with the highest state of charge (SOC) reach the charging upper limit, even if other cells can be charged. Whereas, when discharging, the BECM stops discharging when cells with the lowest state of charge (SOC) reach minimum charging, even if other cells can be discharged. As a result, the amount of high voltage battery power that can be used is reduced, which reduces the remaining distance-to-full discharge.

• The BECM reduces the variation in the amount of charge between cells by discharging power from cells with a high state of charge (SOC) to increase the amount of power that can be used and assure the remaining distance-to-full discharge.

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Block Diagram

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Operation

• The BECM calculates the state of charge (SOC) of each cell from the voltage of each cell in the high voltage battery, the temperature of each module, and the high voltage battery electrical current.

• The BECM discharges power from cells with a high state of charge (SOC) by driving the discharge circuit in the BECM if there is a large variation in the state of charge (SOC) between cells. As a result, variation in the state of charge (SOC) between cells is suppressed.

― Large variation in calculated state of charge (SOC) between cells

― EV system status signal input via CAN communication from PCM indicates that main power is switched OFF or high voltage battery is normal charging

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