!!!MOM!!! Craigslist is still being stupid!!!

Roger that!
When I was a kid, I used permanent magnet motors as generators on little 4th grade science projects and such.
My friend claimed they stuck a car battery directly to a generator on some old car and cranked the motor over. Dunno 'bout that.

This thread is getting pretty cool.

Actually a motor can be a generator can be a motor can be a generator

That is why older generator systems HAD to have what is called a "cut out relay."

Really old systems, before regulators came along, were a single cutout relay in a can. Regulators included the regulator. Automotive generators are not "self limiting" so they must also have a current regulator, hence the three relays in a generator type regulator ---- voltage regulator, current limiter, and cutout relay

Now the REASON you need a cutout is, that if the generator stops charging due to a problem, or is shut down, OR breaks a belt, it tries to become a MOTOR, and I, in fact have had that happen a couple of times in my "yute." If you break a belt with the engine running, the cutout doesn't trip, and the generator sits there spinning wildly, until you either disconnect one of the regulator connections, or wedge a tree branch, etc, against the pulley.