Comment by tomn
10 months ago
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.
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.
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.
When you are riding the bike in the city, the light is not for you to see things, it is for others to see and notice you.
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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.
Not with a hub-type one. These work magnetically and you basically obly lose the 3-5W of power they produce.
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I don't even notice a difference.
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.
I suppose you’re a casual cyclist and you don’t commute on a daily basis.
If you commute on a daily basis, a hub dynamo and light system is a bliss. Just hop on the bike and go. I have used bikes with Shimano, SP and Son for thousands of kms in all kind of weather and never really experienced a fault. It’s as simple as car lights - you just take them for granted.
With battery powered lights you need to take them off and put them back; recharge them; remember to bring them with you and not lose them. A spare battery pack is not enough (front and rear) and may not work during cycling (not all lights can be charged while turned on). And, low quality battery powered lights tend to quickly break (2-3 years) while I now realize one of my b+m systems is 10y old already. Good battery powered lights will probably last more, but they’re as expensive as dynamo powered ones.
So yeah, battery is ok and cheap for casual cycling, but very suboptimal if you want reliable lights every day throughout the year.
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Typical non-hub dynamo lasts like 30 years parked outside, and nice ones cost like $10 on Amazon. You smack it and they start whining at you. They are only barely more complicated than a stew pan.
Hub dynamos seem a bit more fragile, with a wire extending into the lightbulb, but never heard reliability is a concern with it...
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And then you have to worry about recharging/replacing two batteries instead of one. Yay for progress!
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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.
They make a ton of sense when you’re riding long distance and when you don’t have access to a charger.