My three-penn'orth.
Used to use a Smart Halogen headlight set
like this one, 1 x 2w/1 x 10w lo hi beam with lead/acid battery. Heavy(ish), bulky but did the job OK and to be honest, for the money they were a pretty good buy. But I grew jealous of all of the people I saw with nice compact light units, plus which the battery snuffed it in the Smart set

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Next up was a Cateye HL - EL600 RC, which my first commute proved was hopeless, despite the salesman in the shop saying it was 'really bright' and it looked it in the shop in daylight. At night, on my regular commute run it was terrifying. When I re-read (carefully this time) Cateye's own description of this light I realised it was called their 'ultimate
URBAN commuter light' so bloody useless for me.
Still pursuing my you-don't-have-to-shell-out-a-fortune-to-get-goor-lights policy, I bought a NiteFlux Visionstick Halogen 10, which was (a) bulkier than it needed to be and (b) still not bright enough, so I had to use it in conjunction with the Cateye which
just allowed me to see enough, as long as it wasn't raining. The fact that the NiteFlux was a clearance offer should have rung a warning bell!
As I'd already bought the aforementioned Halogen 10 kit and therefore had the charger, battery, leads, mounts etc I then bought, from Australia where they make them, A Niteflux Enduro 8 LED headlamp unit. At 500 lumens this was finally bright enough, on it's own, to see by so I was happier.
I dabbled with the outer fringes of building my own, but afer waiting an inordinately long time for the company I ordered the components from to deliver (4-5 months!

) my enthusiasm, not to mention hours of daylight, had receeded.
So after much looking, shopping around, reading reviews and prevaricating, I swallowed hard, took a very deep breath and invested in a Lupine Tesla 5, which thus far has proven superb as I can actually use it on its low-power setting and still see where I'm going for much of my ride. Since much of my ride is un-lit rural roads I hope this says how good it is.
To sum up and distill the above;
- With lights, sooner or later, you get what you pay for, whether this be poorer than expected performance, poor spares/service backup, fragility of componenents etc.
- Buy once, buy well (my new motto). What seems like a lot of money at the time is money well spent, and saves on dental bills (from anguished gnashing of teeth)!
- Anything below 500 lumens will not allow you to ride at daylight speed in the dark on an un-lit road.
- Definitely consider the new Schmidt SON Delux hub dynamo and Edelux headlamp. I was only put off as the total cost really was more than I could afford but they are well made, have good spares backup and are properly lensed so they don't dazzle motorists.
These are, of course, my opinions and will doubtless be countermanded/shredded by fellow forum members shortly

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p.s. my HL - EL600RC and Visionstick Enduro 8 are currently for sale on a cetain auction site if anyone's interested.