Electric Power Management; Battery Run-Down Protection - Hummer 2009 H3 Owner's Manual

Electric Power
Management
The vehicle has Electric Power
Management (EPM) that estimates
the battery's temperature and
state of charge. It then adjusts the
voltage for best performance
and extended life of the battery.
When the battery's state of charge
is low, the voltage is raised
slightly to quickly bring the charge
back up. When the state of charge is
high, the voltage is lowered
slightly to prevent overcharging. If
the vehicle has a voltmeter gage or
a voltage display on the Driver
Information Center (DIC), you may
see the voltage move up or
down. This is normal. If there is a
problem, an alert will be displayed.
The battery can be discharged
at idle if the electrical loads are very
high. This is true for all vehicles.
This is because the generator
(alternator) may not be spinning fast
enough at idle to produce all the
power that is needed for very high
electrical loads.
A high electrical load occurs when
several of the following are on, such
as: headlamps, high beams, fog
lamps, rear window defogger,
climate control fan at high speed,
heated seats, engine cooling fans,
trailer loads, and loads plugged into
accessory power outlets.
EPM works to prevent excessive
discharge of the battery. It does this
by balancing the generator's
output and the vehicle's electrical
needs. It can increase engine
idle speed to generate more power,
whenever needed. It can temporarily
reduce the power demands of
some accessories.
Normally, these actions occur in
steps or levels, without being
noticeable. In rare cases at the
highest levels of corrective action,
Instrument Panel
this action may be noticeable to the
driver. If so, a Driver Information
Center (DIC) message might be
displayed, such as BATTERY
SAVER ACTIVE, BATTERY
VOLTAGE LOW, or LOW BATTERY.
If this message is displayed, it is
recommended that the driver reduce
the electrical loads as much as
possible. See DIC Warnings and
Messages on page 3-37.
Battery Run-Down
Protection
This feature shuts off the dome
lamp if it is left on for more
than 20 minutes when the ignition is
in LOCK/OFF. This helps to
prevent the battery from being
drained.
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