ON the alternator dropping voltage you might examine the ballast resister, this controls the field strength. Oft times they resist down to provide 9 volts or less. too much less and the field drops out, too much voltage and the field is putting out more than it is designed for. If they are weak their voltage can drop off rather quickly with heat. In older cars some times it's a porcelain block and in boats it is often a special wire .
First, before anyone posts to let me know, I do realize this thread was started in 2005. But, I don't think I have ever had the opportunity to use the following emoticon, on this forum (or any forum, for that matter):
My Honda gx200 powered ACdelco DR44G alternator welder is fully functional. It's current configuration is to be a welder but it could be a battery charger with a universal voltage regulator. Note: To be a 12 or 24v battery charger you don't have to convert the alternator to external rectifier and external field power.