Nissan Altima HL32 Hybrid. Manual - part 543

BATTERY CONTROL

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BATTERY CONTROL

System Diagram

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System Description

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BATTERY SMART UNIT

• The battery smart unit detects and transmits the HV battery condition signals (voltages, currents, and tem-

peratures), which are used to determine charging or discharging values, to the hybrid vehicle control ECU.

• The battery smart unit also detects and transmits the cooling fan voltage signals which are necessary to

effect cooling fan control, to the hybrid vehicle control ECU.

• A leak detection circuit is provided in the battery smart unit in order to detect any excessive current draw

from the HV battery.

HV BATTERY

General

• The ALTIMA Hybrid model uses sealed nickel metal hybrid (Ni-MH) HV batteries. The HV batteries have a

high power density, are lightweight and offer longevity to match the characteristics of the Hybrid Vehicle

Control System. Because the Hybrid Vehicle Control System effects charge/discharge control to maintain

the HV batteries at a constant SOC (state of charge) level while the vehicle is operating normally, it does not

need to be recharged externally.

• The HV batteries use nickel-plated, metal container type cells to realize enhanced cooling performance and

a compact construction. As a result, high power density, lightweight construction, and longevity have been

accomplished at high levels.

• The HV battery unit consists of 34 separate batteries. The batteries each comprise 6 cells and they are con-

nected to each other in series through a bus bar module. The cells of the batteries are connected at two

locations in order to reduce the internal resistance and improve efficiency. The HV battery unit, which has a

total of 204 cells (6 cells 

×34 batteries) and a nominal voltage of 244.8 V (1.2 V ×204 cells), is located in the

luggage compartment behind the rear seat.

• A junction block, battery smart unit and DC/DC converter are used. Integrated into the junction block are an

SMRG (System Main Relay Ground), SMRB (System Main Relay Battery) and a current sensor.

The battery smart unit monitors the HV battery. The DC/DC converter supplies power to the auxiliary battery

after decreasing the nominal voltage of DC 244.8 V supplied by the HV battery to DC 12 V. Power to the

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BATTERY CONTROL

lights, audio system, air conditioning system (except the electric inverter compressor) and ECUs is supplied

by the auxiliary battery.

The battery smart unit, junction block, and DC/DC converter are located in the battery front side carrier,

which is in the same housing as the HV battery unit. This realizes a compact package.

• An air-cooling method, which uses a dedicated cooling fan to cool the HV battery with air from inside the

cabin, is employed. A dedicated cooling fan is also provided for the DC/DC converter. Thus, highly efficient

air-cooling has been achieved.

• A service plug that shuts off the circuit is provided in the middle of the HV battery modules (between No.15

and No.16 batteries). Before servicing any portion of the high-voltage circuit, be sure to remove the service

plug.

DC/DC Converter

The power source for auxiliary equipment of the vehicle such as the lights, audio system, and the air condition-

ing system (except electric inverter compressor), as well as the ECUs, is based on a DC 12 V system.

Because the HV battery outputs the nominal voltage of DC 244.8 V, the converter is used to transform the volt-

age from DC 244.8 V to DC 12 V in order to recharge the auxiliary battery.

Junction Block

A junction block, in which an SMRG and SMRB are integrated, is used.

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BATTERY CONTROL

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Service Plug

By removing the service plug before performing any inspection or service, the high-voltage circuit is shut off at

the intermediate position of the HV battery, thus ensuring safety during service.

The service plug assembly contains a reed switch for interlock. Lifting the clip lock up turns OFF the lead

switch, which shuts off the SMR. However, to ensure safety, make sure to turn OFF the ignition switch before

removing the service plug.

1.

Service plug

2.

Battery temperature sensor 0

3.

Battery smart unit

4.

SMRG

5.

SMRB

6.

Battery current sensor

7.

HV converter

8.

battery temperature sensor 3

9.

Intake temperature sensor

10. Battery temperature sensor 2

11. Battery temperature sensor 1

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The main fuse for the high-voltage circuit is provided inside of the service plug assembly.

NOTE:

After the service, please do not start the system until the service plug is connected.

HV BATTERY AND DC/DC CONVERTER COOLING SYSTEM

HV Battery Cooling System

• A dedicated cooling system is used to ensure that the HV battery performs properly, despite it generating

significant heat during the repetitive charge and discharge cycles.

This cooling system employs an air-cooling method, which uses the dedicated cooling fan to cool the HV

battery with air from inside the cabin.

• The air from inside the cabin, which is introduced through the intake duct located on the rear package tray

trim, flows downwards through the battery module, reducing the temperature of the battery module, and is

emitted from the vehicle through the exhaust duct.

• The hybrid vehicle control ECU controls the operation of the cooling fan for the HV battery. The hybrid vehi-

cle control ECU receives the signals from the battery temperature sensor, which is built into the HV battery,

via the battery smart unit. Then, it controls the cooling fan in order to control the battery module temperature

appropriately.

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