Nissan Altima HL32 Hybrid. Manual - part 538

HYBRID BATTERY SYSTEM

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• The battery smart unit monitors the voltage of the cooling fan, which is needed by the hybrid vehicle control

ECU to effect cooling fan control, and transmit it to the hybrid vehicle control ECU via serial communication.

SMR (SYSTEM MAIN RELAY) CONTROL

(1) General

The SMR is a relay that connects and disconnects the power source of the high-voltage circuit upon receiving

a command from the hybrid vehicle control ECU.

A total of three relays are used: one (SMRB) at the positive side, and two (SMRP and SMRG) at the negative

side. One (SMRP) of the relays at the negative side is a semiconductor relay, which is integrated in the DC/DC

converter. The other two are contact point type relays, which are mounted on the junction box in the HV bat-

tery module.

(2) Power is ON

The hybrid vehicle control ECU turns the SMRB ON. After that, it turns the SMRP ON.

After the hybrid vehicle control ECU has turned the SMRG ON, it turns the SMRP OFF.

JMCIA0121GB

JMCIA0064GB

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HYBRID BATTERY SYSTEM

As the controlled current is initially allowed to pass through a resistor in this manner, the contact point in the

circuit is protected from damage that could be caused by a rush current.

(3) Power is OFF

• First, the hybrid vehicle control ECU turns the SMRG OFF. After it has determined whether the contact

points of the SMRG are stuck, it turns the SMRB OFF.

• Afterwards, the hybrid vehicle control ECU turns the SMRP ON in order to determine whether the contact

points of the SMRB are stuck. Then, it turns the SMRP OFF.

JMCIA0065GB

HYBRID BATTERY SYSTEM

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• If the hybrid vehicle control ECU detects that the contact points are stuck, it illuminates the master warning

light and indicates “CHECK HYBRID SYSTEM” on the multi-information display, and stores a DTC (Diagnos-

tic Trouble Code) in memory.

SOC CONTROL

• The hybrid vehicle control ECU calculates the SOC (state of charge) of the HV battery by monitoring its

charging and discharging amperages, in order to effect condition control.

• While the vehicle is in motion, the HV battery undergoes repetitive charging/discharging cycles, as it

becomes discharged by the MG2 during acceleration and charged by the regenerative brake during deceler-

ation. The hybrid vehicle control ECU calculates the SOC based on charging/discharging levels detected by

the current sensor. The hybrid vehicle control ECU performs the charging/discharging control based on the

calculated value in order to steady the SOC at its target level anytime.

POWER CABLE

The power cable is a high-voltage, high-amperage cable that connects the HV battery module with the

inverter, the inverter with MG1 and MG2, and the inverter with the electric inverter compressor. The power

cable starts at the connector of the junction block of the HV battery, which is located behind the rear seat.

It passes under the floor panel, along the side of the floor reinforcement, and connects to the inverter in the

engine compartment. The power cable is shielded in order to reduce electromagnetic interference.

JMCIA0066GB

JMCIA0067GB

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HYBRID BATTERY SYSTEM

For identification purposes, the high-voltage wiring harness and connectors are color-coded orange to distin-

guish them from those of the ordinary low-voltage wiring.

JMCIA0063GB