Electric Power Management; Battery Run-Down Protection - Chevrolet 2009 TrailBlazer 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
3-18
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,
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 3-51.

Battery Run-Down Protection

This feature shuts off the dome, courtesy, and vanity
lamps if they are left on for more than 20 minutes when
the ignition is off. This helps to keep the battery from
running down.
If the battery run-down protection shuts off the interior
lamps, it may be necessary to do one of the following to
return to normal operation:
•
Shut off all lamps and close all doors.
•
Turn the ignition key to ON/RUN.
This feature also turns off the parking lamps and
headlamps under most circumstances, if they are left
on. Turn the exterior lamps knob to turn them back on.