Depends on the vehicle. Some go to the starter main lug, some like chevys 60s go to what is called a buss bar on the horn relay; it's just a convenient place to hook up large wires.

Going to the batt term is not used much, probably due to corrosion. Some do though, like my driver VW wagon.

 

Either method will work.

-- On my older GMC truck the stock 10si alternator was connected from the Bat terminal to the main lug on the starter, with a fusible link, and then the large diameter positive cable ran from the main lug up to the battery.

-- When I switched to a higher 94 amp 12si alternator I ran an 8 gauge wire directly over from the alternator Bat terminal to the battery positive, and added the right size fusible link. I like this setup because troubleshooting is easier. It also works well for my application because both battery and alternator are on the passenger side, so the cable is short.

-- On some newer GM trucks (mid 90's), a direct wire from the alternator to the battery was the factory setup.

Bruce

 

I ran my alt output to the terminal block on the firewall. Then ran the battery charging wire to the battery from the TB. As a matter of fact- I ran just about every darn thing to the terminal block(s) on the firewall

Nooj

 

I've seen that setup as the stock wiring for a late 80's GM pickup. It seems to be a better solution than using the lug on the starter, where the wires are very exposed to water and dirt.

Bruce