I have a Freeplay light, not sure whether it's the particular version you're talking about.
Mine has a two element bulb for high and low beam and two small (and low capacity) Ni[Cd|MH] batteries, in addition to the crank-up generator. It would be possible to use the generator to charge the batteries, but you would have to spend several days cranking and then letting the spring run the generator to fully charge the batteries. This matters, because the generator doesn't have enough guts to run the bulb on high. Fortunately, there is a plug in charger, but that sort of defeats the purpose, I think.
So, once you've run the batteries down, you get a crank light that runs for 3 minutes (that's how long the spring drives the generator) on low. Then you're in the dark for a couple of minutes until you get the spring rewound.
On the bright side, the machine seems to be fairly high quality, and looks as if it should last a long time. On the dim side, it's HUGE for the amount of light it puts out, even on high beam. It's heavy. It isn't practical to use as a crank light, as I explained above.
Over all, I'm very dissatisfied with my Freeplay light. I got it on sale for $10, without the option to return it. Once I got it home, I could see why they had to mark it down so far to move it, and I would have returned it if I could.
One of these days I'll check to see if one of the Minimag LED drop-ins will fit in place of the tri-pin bulb. The little Nite-ize drop-in might make the batteries last long enough to let it run a few minutes between cranking spells, but that's a huge body for such a dim little bulb.
Hopefully the one you're looking at is more practical than mine.
Nels