2011 Chevrolet Impala Owner's Manual - Page 172

6-8 Lighting 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 messages displays, it is recommended that the driver reduce the electrical loads as much as possible. See Driver Information Center (DIC) on page 5‑26. If the vehicle has a voltmeter gauge 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. Battery Power Protection This feature helps prevent the battery from being drained, if the interior courtesy lamps, reading/ map lamps, visor vanity lamps, or trunk lamp are accidentally left on. If any of these lamps are left on, they automatically turn off after 10 minutes, if the ignition is off. The lamps will not come back on again until one of the following occurs: . . The ignition is turned on. The exterior lamps control is turned off, then on again. The headlamps will time out after 10 minutes, if they are manually turned on with the ignition on or off.