MC (11-09 08:08):
Speaking of a voltage as a “load” makes no sense in electrical theory/engineering. Are the instructions worded that way? If you just run your alternator on your own healthy battery, you have it charging through some resistance into the 12-volt voltage source that is your battery. If you put someone’s battery that is dead, but is not shorted, across your battery, you have essentially the same thing. If you took your battery out of the circuit, leaving the bad battery in (which I wouldn’t expect you to do), maybe some condition is set up that is harmful to the alternator, but I wouldn’t, off hand, understand what that would be.
Almost all the time, a dead battery is simply the result of a light being left on or battery that won’t take a sufficient charge or a defective charging system (in the car with the bad battery), in all of which cases, the charging shouldn’t hurt the alternator in the servicing car. Almost always, a successful start will take the party to where they can go prior to their next stopping their engine.
torq:
I would call a shorted (across all cells) battery an infinite load, not a situation of “no load”.
Ray