I would hook it at the battery. The alt will have too much demand if you hook it right at the alt. It is best to feed from the reserve of the battery, and allow the ECU to make it's calculations based on the battery readings. In many cases there are inductive probes inline on the feed wires from the battery to the alt. So it is best to avoid linking downstream of the battery. But he is doing the big 3 so I can't see any difference if connected to either. The inductive probes read current. If you pull amplifier current from a charging stud on an alt it pulls reserve current to the alt through the inductive probe. Burp your system and amp clamp the power wire to the amp. Next, burp the system and run the amp clamp between the alt and battery. Get back to me with the results . Even running the big 3 you have the current load increased exponentially through the main alt feed if you attach the amp power to the alternator on the factory line. You can almost think of battery reserve as a shock absorber. I still can't understand how with the proper gauge and length wires done for the big 3, there will be a difference between connecting to the battery or the alternator. How will there be any difference when it's like one big continuous wire and it's just either of the sources connected first then second? With the big 3 added to the picture I see it as a singular wire that all the power is passing through. Both the alternator and the battery are on that wire. At which end you attach the wire that goes into your amp is no different than the other. If you connect to the battery it's just like you used an extension that connects to the alternator.