I have a 2014 Ford Focus SE that i use as my Work Vehicle. I work in Emergency Roadside Assistance. I have to run a laptop In the car in order to direct calls to other employees and charge a hotspot and phone. Recently i have been interested in adding an amplifier and Sub into the car as i spend 12 hours a day driving to calls. I have the laptop and chargers running through a 140amp/400amp(Peak) power converter. My father is a mechanic and has expressed some concern about adding the amp and sub into the vehicle with everything else the vehicle is running already. Im looking for any ideas that dont involve adding a second batter unless that is my absolute only way. Please assist with any positive and negative side affects of option.