well 3k rms at 13.8 volts is 217 amps which would leave roughly 50 -60 amps for rest of the car ... stock alt is 80-100 amps a car uses roughly 60-70% of capacity so 60 to 70 amps would be for the car .that would leave me drawing 10 to 20 amps over output . I plan on a overdrive pully to get full output as close to idle as i can