[tomn]

I get why people like them, but they make way less sense when you work out the capacity of an equivalent weight (not to mention cost) of lithium cells.

It's easy to get to about 90Wh, which will run a dynamo-powered light for 30 hours on max (most dynamos seem to be rated 3W).

There are definitely cases where it makes sense, and not having to keep batteries charged is nice, it's just easy to miss how good batteries are these days.

[tomsmeding]

Not having to take the light off the bike and charge it and then forget to take it back to the bike, not to mention forgetting charging it and finding out when it's dark, is completely worth having a dynamo.

[franciscop]

I live in Tokyo, and only drive in the city center. 90% of me having a light is the legal requirement of having so, I virtually never need it since the streets I usually ride are well-lit. The remainder 10% is that I like the solid feel of the bike overall and felt sad for the integrated light not to work TBH.

[pmontra]

In my experience engaging a dynamo is worth one switch of the gear on a 7 gear cassette. I accept the tradeoff of having to pocket the light.

[tomn]

A spare battery in your saddle-pack solves most of those problems.

If you're worried about being without light, a (typical) dynamo system is more complicated and exposed than a battery system, so will be more prone to failure.

[Aardwolf]

It's not about weight, it's about having the light work when you need it.

Ensuring the battery is not empty at the time you want to ride it and it is night is not always convenient

I'm talking about commute, not sports, here.

[fatfox]

They make a ton of sense when you’re riding long distance and when you don’t have access to a charger.