I'm not going to say this won't work and I will say that I didn't look at the website very good, but from the picture I saw and the way you describe it, I can see both it working and not working.

The way you describe it, I can see it working. Having separate batteries to be able to have a motor big enough to spin a compressor fast enough to produce boost is possible. Then you could use the alternator to charge it back up as needed. A couple of diodes to keep backfeeding and you're all set. Now, here's the problems I see. First off a bank of batteries, three starters, the blower unit, and everything needed to set this thing up is going to add lots of weight. Adding weight is just like taking away horsepower. If the supercharger can over-come that weight, then fine, but from the looks of it, I don't see it happening. One other downfall I see is that a starter motor generally doesn't spin fast enough to run a compressor wheel to make any boost. Three of them isn't going to speed up the RPM, but will add the muscle needed to turn the blower. Now, starters generally are short draw motors. They get hot and tend to burn out if run for more than a few minutes or so at a time. Even if there were a gear box that over-drives the starters to the blower and could spin the rotors in the blower fast enough, the load on the starter motors go up the more you over-drive them. Just like any other electric motor, when you load them up, you draw more current. More current is going to drain your batteries quicker. Three starters drawing current is going to suck a battery dry in nothing flat. So, what? Add more batteries? Ok, every battery you add in parallel gives you that much more reserve cranking time for the starters... guess what? You are adding around 50lbs of weight each and every time you add a battery. 100 lbs is a 10th of a second in acceleration. Do you know how much HP it takes to add on to gain a 10th of a second? I can tell you it's a lot. So, by adding the weight, you not only have to make enough power to over come weight you just put in, you have to produce more power over and above that to make a power increase over what you started with...
I can see this working, but I don't see it working efficiently. Again, if it was that easy, racers would be using them and so would manufacturers.


On to the previous discussion about magnets and alternators.
Generators used on cars from maybe the mid-60's and back used generators. Generators did use magnets and were very big and inefficient. Alternators do not use magnets, as mlclark pointed out. They use an armature and a stator. The armature is the spun inside the stator which is where the fields are broken. As mlclark also stated, the fields must be charged. You can't just spin an alternator and produce current. You have to energize the alternator while it's spinning to be able to produce results. Generators, on the other hand, did not require energizing. Like a magneto, they just required that you spin them to produce electrical energy. A generator produces DC current. An alternator produces AC current. As he also stated, once the alternator produces the AC current, it's recitified in to DC and passed through a regulator to keep it's voltage in the range needed for automobiles (generally 13-14.5 volts). Do alternators and generators do the same thing? Well, yes and no. The end result is the same. As far as the end user is concerned, yes they do the same thing. As far as the scientific community and automobile mechanics who have to troubleshoot the problems, no, they are not the same.