alt Hacker NewsIn the Netherlands many people use these kinds of detachable bike lights. I've never came across soldered batteries in the dozen or so I've replaced batteries for. Not always cheaper, but just tossing the whole thing seems like such a waste.
Well done!
There are also dynamo powered LED lights which only provide light while riding the bike, and about a minute afterwards (I assume from an internal capacitor). They are not detachable but why would that be necessary? From what I can tell they also don't require regular replacement.