I've got a rechargeable Niterider that I bought for about $60 on sale at REI. It has a 6w and 10w bulb, good light for my riding, have an hour or so with both bulbs running, or turn one off for longer.
I had a bottle-type generator when I was a teenager 30 years ago. The headlight was bright enough that I could see the chuckholes before I rode into them. That was about it- pretty pitiful. But a heck of a lot better than nothing. It had noticeable drag, but not bad.
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"be careful this rando stuff is addictive and dan's the 'pusher'."