2008 GMC Canyon Owner's Manual - Page 150

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, 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 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. 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. This will help prevent your battery from running down. Accessory Power Outlet(s) The accessory power outlets can be used to connect electrical equipment such as a cellular phone or CB radio. Your vehicle may have two accessory power outlets located on the lower part of the instrument panel below the climate control system and there may be one located on the rear of the center console. A small cap must be pulled down to access an accessory power outlet. When not using an outlet be sure to cover it with the protective cap. Notice: Leaving electrical equipment on for extended periods will drain the battery. Always unplug electrical equipment when not in use and do not plug in equipment that exceeds the maximum amperage rating of 20 amperes. 3-18