Chuck Sherwood wrote:
Since all the OP wants is some lights in the "pool"
how about a different approach. Small DC motors make
good generators. Perhaps they would work better at
low speeds and low power than a fairly large car alternator.

I recently saw some plans were a guy made his own alternator
for a direct drive wind generator so that he didn't need any
gears or chains to increase the rotor speed to make the
generator work.

chuck

Actually, most of the cheap DC motors I am familiar with require MORE
speed than an automotive alternator. Also, with these DC motors it is
very hard to regulate the output voltage- you have to control speed or
put in a regulator in series with output, an inefficient method.

I'd go ahead and add a battery- small cycle or lawn tractor one- to the
alternator. If it has an internal regulator, fine, otherwise add one.
You need that to keep from burning out the light. You also need to add
some sort of switch so that the light only comes on when wheel is
turning, to keep from running the battery down, but that shouldn't be
too hard to rig up