Posted for Tubamanflies@aol.com:

Cy is correct.  If the voltage regulator is working the size of the alternator does not mater.  It will put out enought current to bring the buss voltage up and then taper back. As the load increases the alternator just responds with more juice until it can't keep the buss voltage up.  It is then up to the battery.  If the regulator goes south, worse case full field voltage the current output of even the smallest unit will be too much for most batteries if left for very long.

And yes the only wire that maters is the one from the alternator to the buss.  This is usally protected with a large breaker.  The field wire is probably a non issue.

Ray