gauge of wire for Alternator to battery?

[Mike Pearson]

If you put an ammeter on the wire you could tell what the alternator is actually putting out to the battery. I would say its no where near 140 amps. Size the wire on the actual load. Thats probably why the small wire has been working for you. Just remember the lower the voltage the higher the amperage is. Thats why the starter has such a large cable going to it.