Hook it to the joint and here's why.
http://www.madelectrical.com/electri...esensing.shtml
Not only that, but if you have an ammeter dash gauge then you will not be able to get the ammeter to work unless it is wired to the joint, so that there is a shunt between the battery and the alternator feed wire. I can get into this more but it can be a little technical. Can you provide more details on what system you have. Alternator type, internal or external regulator, type of dash gauge idiot light or ammeter and what wires you have. The 3 wire alternator SI conversions work better and provide more amperage output.