Be careful using the alternator to charge a low battery. The newer alternator circuits are not robust enough to handle that kind of current for such a long time and many will overheat and fail, or the life of the alternator will be reduced. If you need to charge your chassis battery, hook it to a charger.
I took my alternator in to have it rebuilt and the guy pulled out the regulator on a newer GM 350 alternator and then showed me one from the early 80s. The newer circuit board was about the size of a quarter with very small components. The older one was quite robust. It seems from looking at the newer board that the newer alternators are quite fragile.
I'm sure people will have different opinions and I'm interested in hearing them.
