Can your alternator keep up? A factory unit is sized to handle the electrical demands of your average auto user along with an extra margin of power. However, start adding on lights, a winch, or high-power audio system and you may begin to overtax the charging system. In these cases, an upgraded alternator may be in order to meet the added current consumption. A vehicle idling presents the worst case scenario as an alternator has its poorest power output at low running speeds.