Well, I'm sure I'm in way over my head and probably can't offer many useful ideas. But I'll take a stab. Myself, I'd suspect a problem with the alternator.

You sure the alternator can't put out that sort of power? Recall that you guys flipped out when I said that I had disconnected my battery when the car was running and my measured system voltage shot up to 16... You all told me that I had narrowly avoiding burning up all my wires... Maybe you've got a similar problem?

When the electric motor in my old portable tablesaw went out, it started pulling a lot of extra power and kept tripping the 15 amp breaker. Admittedly an electric motor is a different beast, but I think that the alternator can put out a lot more... ahem... err... current? voltage? amps? generally... "juice" (uh-oh here comes Ron Kwas to correct my usage of "juice"). If it is failing in some way?

My household wiring knowledge tells me that wire gauge is integral to proper amperage and too small a wire (say 14 gauge) is too small for a 20-30 circuit. Could the wire be burning up under too many amps? Maybe it's some problem with the battery as ballast?

Just a few cents...