Hummer H3. Manual — part 68

Batteries that are no longer wanted must be disposed of by an approved battery recycler and must
never be thrown in the trash or sent to a landfill.

Batteries that are not part of the vehicle itself, not the battery under the hood, must only be
transported on public streets for business purposes via approved hazardous material transportation
procedures.

Battery storage, charging, and testing facilities in repair shops must meet various requirements for
ventilation, safety equipment, material segregation, etc.

The maintenance-free battery is standard. There are no vent plugs in the cover. The battery is
completely sealed except for 2 small vent holes in the side. These vent holes allow the small
amount of gas that is produced in the battery to escape.

The battery has 3 functions as a major source of energy:

Engine cranking

Voltage stabilizer

Alternate source of energy with generator overload

The battery specification label, example below, contains information about the following:

The test ratings

The original equipment catalog number

The recommended replacement model number

the skin. Flush immediately and thoroughly any contacted
areas with water and get medical help.

Follow each step of the jump starting procedure in order.

Treat both the booster and the discharged batteries
carefully when using the jumper cables.

IMPORTANT: Because of the materials used in the manufacture of automotive

lead-acid batteries, dealers and service shops that handle them
are subject to various regulations issued by OSHA, EPA, DOT,
and various state or local agencies. Other regulations may also
apply in other locations. Always know and follow these
regulations when handling batteries.

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

Fig. 96: View Of Battery Specification Label
Courtesy of GENERAL MOTORS CORP.

Battery Ratings

A battery may have 3 ratings:

Amp hour

Reserve capacity

Cold cranking amperage

When a battery is replaced, use a battery with similar ratings. Refer to the battery specification
label on the original battery or refer to Battery Usage.

Amp Hour

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

The amp hour rating of a battery is the amount of time it takes a fully charged battery, being
discharged at a constant rate of 1 amperes and a constant temperature of 27°C (80°F), to reach a
terminal voltage of 10.5 volts. Refer to Battery Usage for the amp hour rating of the original
equipment battery.

Reserve Capacity

Reserve capacity is the amount of time in minutes it takes a fully charged battery, being
discharged at a constant rate of 25 amperes and a constant temperature of 27°C (80°F), to reach a
terminal voltage of 10.5 volts. Refer to Battery Usage for the reserve capacity rating of the
original equipment battery.

Cold Cranking Amperage

The cold cranking amperage is an indication of the ability of the battery to crank the engine at
cold temperatures. The cold cranking amperage rating is the minimum amperage the battery must
maintain for 30 seconds at -18°C (0°F) while maintaining at least 7.2 volts. Refer to Battery
Usage for the cold cranking amperage rating for this vehicle.

CHARGING SYSTEM DESCRIPTION AND OPERATION

Electrical Power Management (EPM) Overview

The Electrical Power Management (EPM) System is designed to monitor and control the
charging system and send diagnostic messages to alert the driver of possible problems with the
battery and generator. This EPM System primarily utilizes existing on-board computer capability
to maximize the effectiveness of the generator, to manage the load, improve battery state-of-
charge (SOC) and life, and minimize the systems impact on fuel economy. The EPM System
performs 3 functions:

It monitors the battery voltage and estimates the battery condition.

It takes corrective actions by adjusting the regulated voltage.

It performs diagnostics and driver notification.

The battery condition is estimated during key-off and during key-on. During key-off the SOC of
the battery is determined by measuring the open-circuit voltage. The SOC is a function of the acid
concentration and the internal resistance of the battery, and is estimated by reading the battery
open-circuit-voltage when the battery has been at rest for several hours.

The SOC can be used as a diagnostic tool to tell the customer or the dealer the condition of the
battery. Throughout key-on the algorithm continuously estimates SOC based on adjusted net amp

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

hours, battery capacity, initial SOC, and temperature.

While running, the battery degree of discharge is primarily determined by a battery current
sensor, which is integrated to obtain net amp hours.

In addition, the EPM function is designed to perform regulated voltage control (RVC) to improve
battery SOC, battery life, and fuel economy. This is accomplished by using knowledge of the
batteries SOC and temperature to set the charging voltage to an optimum battery voltage level for
recharging without detriment to battery life.

The Charging System Description and Operation is divided into 3 sections. The first section
describes the charging system components and their integration into the EPM. The second section
describes charging system operation. The third section describes the instrument panel cluster
operation of the charge indicator, driver information center messages and voltmeter operation.

Charging System Components

Generator

The generator is a serviceable component. If there is a diagnosed failure of the generator it must
be replaced as an assembly. The engine drive belt drives the generator. When the rotor is spun it
induces an alternating current (AC) into the stator windings. The AC voltage is then sent through
a series of diodes for rectification. The rectified voltage has been converted into a direct current
(DC) for use by the vehicles electrical system to maintain electrical loads and the battery charge.
The voltage regulator integral to the generator controls the output of the generator. It is not
serviceable. The voltage regulator controls the amount of current provided to the rotor. If the
generator has field control circuit failure, the generator defaults to an output voltage of 13.8
volts.

Generator Battery Control Module

The generator battery control module is a class 2 device. It communicates with the engine control
module (ECM), instrument panel cluster and the body control module for electrical power
management (EPM) operation. It is a serviceable component that is connected to the negative
battery cable at the battery. It directly controls the generator field control circuit, charge
indicator control, input to the generator. It continuously monitors the generator field duty cycle
signal circuit and the battery voltage. If the generator battery control module loses
communication with the ECM, the default voltage will be set to 13.8 volts and the module will
set U1016. If the generator battery control module loses communication with the body control
module (BCM), the module will set U1064.

Engine Control Module (ECM)

2008 Hummer H3

2008 ENGINE Engine Electrical - H3