5-6
12 V Starting and Charging
Description and Operation
Battery Description and Operation
Warning: Batteries produce explosive gases,
contain corrosive acid, and supply levels of
electrical current high enough to cause burns.
Therefore, to reduce the risk of personal injury
when working near a battery:
•
Always shield your eyes and avoid leaning over
the battery whenever possible.
•
Do not expose the battery to open flames or
sparks.
•
Do not allow the battery electrolyte to contact
the eyes or 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.
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
Battery Low Start Vehicle Message
The body control module (BCM) monitors battery
positive voltage to determine battery state of charge.
If one or more of the BCM battery positive voltage
terminals measure less than approximately 11.6V
compared to the BCM ground circuits, this message will
display and four chimes may sound. Start the vehicle
immediately. If the vehicle is not started and the battery
continues to discharge, the climate controls, heated
seats, and audio systems will shut off and the vehicle
may require a jump start. These systems will function
again after the vehicle is started.
Battery Ratings
A battery has 2 ratings:
•
Cold cranking amperage
•
Amperage hours
When a battery is replaced use a battery with similar
ratings. See battery specification label on the original
battery.
Amperage Hours
The amperage hour rating tells you how much
amperage is available when discharged evenly over a
20 hour period. The amperage hour rating is
cumulative, so in order to know how many constant
amperage the battery will output for 20 h, you have to
divide the amperage hour rating by 20. Example: If a
battery has an amperage hour rating of 74, dividing by
20 = 3.75. Such a battery can carry a 3.75 A load for
20 hours before dropping to 10.5 V. (10.5 V is the fully
discharged level, at which point the battery needs to be
recharged.) A battery with an amperage hour rating of
55 will carry a 2.75 A load for 20 hours before dropping
to 10.5 V.
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 V. See battery label for the cold cranking amperage
rating of this battery.
Charging System Description and
Operation
Electrical Power Management Overview
The electrical power management 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 electrical
power management system primarily utilizes existing
on-board computer capability to maximize the
effectiveness of the generator, to manage the load,
improve battery state-of-charge and life, and minimize
the system's impact on fuel economy. The electrical
power management system performs 3 functions:
•
Monitor the battery voltage and estimate the
battery condition
•
Take corrective actions by boosting idle speeds,
and adjusting the regulated voltage
•
Perform diagnostics and driver notification
The battery condition is estimated during ignition/
vehicle off and during ignition/vehicle on. During
ignition/vehicle off the state-of-charge of the battery is
determined by measuring the open-circuit voltage. The
state-of-charge 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.
Any time the ignition/vehicle is on, the vehicle algorithm
continuously estimates battery state-of-charge based
on adjusted net amp hours, battery capacity, initial
state-of-charge, and calculated temperature.
While the engine is running, the battery degree of
discharge is primarily determined by the integrated
battery current sensor, to obtain net amp hours.
2021 - Silverado 4500HD, 5500HD, and 6500HD Electrical Body Builder Manual
