if his alt goes out, then its his alt.. you can tell if you see any dimming in lights when the bass hits.. the cap is also putting stress on your alt because a cap is like a small battery.. once your car is on, the alt is whats running your car, not your battery.. i suggest getting a HO Alt, there is a groupbuy for them with a company called Exessive Amperage, they are really great and the person that makes the product really stands by what he makes. Our imports have weak alts, like 60 amps or so. i would prob get a 140-160amp. Also, upgrade to thicker wires for the battery. I hope this was helpful