Electric Power Management - Pontiac Grand Prix 2007 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 put the charge
back in. When the state of charge is high, the
voltage is lowered slightly to prevent overcharging.
If the vehicle has a voltmeter gage or 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.
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A high electrical load occurs when several of the
following loads are on: 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, this action
may be noticeable to the driver. If so, a Driver
Information Center (DIC) message might be
displayed, such as Battery Saver Active. 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 204.