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This article suggests an efficient dynamo will cost you up to thirty seconds over 100km when switched off and up to nearly six minutes switched on.
Agree with @hippy's point about one less thing to think about, there is a bit more stress with batteries. There's also a little bit more bulk if you are really short of space, and a bit more hassles if it rains to keep stuff dry.
But I think the gains are bigger. Those articles aren't written with ultra racers in mind. The power output for most of us is lower, after a couple of days, so losing 6 W when you're only putting out 80W is more damaging.
But even on those numbers, 6 min per 100km is 5.5 hours, or 100+km, so still worth having. (It's an autumn ride so quite a lot of dark, + gadgets, means people with dynamos would use them most of the time).
frank9755-
https://www.gribble.org/cycling/power_v_speed.html
a) 75 + 15kg, defaults, 80W = 22.76kph
b) 75 + 15kg, defaults, 75W = 22.12kph5474k
a) 240.51
b) 247.47~7hrs better off at the end of IPWR without a dynamo. That's IF you ran the dynamo 24hr/day (which I don't), not taking into account any extra weight of batteries and critically not factoring any charging delays.
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Those articles aren't written with ultra racers in mind. The power output for most of us is lower, after a couple of days, so losing 6 W when you're only putting out 80W is more damaging.
Hadn't thought of that.
But even on those numbers, 6 min per 100km is 5.5 hours, or 100+km, so still worth having.
That did occur to me, but I forgot to mention it.
(It's an autumn ride so quite a lot of dark, + gadgets, means people with dynamos would use them most of the time).
I hadn't thought of that either: Oz = sunshine to me. But that could swing both ways, as more use means more frequent charging.
Ultimately though, an ounce of experience is better than a pound of internet wisdom, so I'm not going to argue with you: I'm just trying to bump my post count...
hippy
Scilly.Suffolk
Would something like what HED do be an idea: ie alu rim with a carbon fairing.
Using rechargeable batteries seems like the worst option to me: you're reliant and dependant upon being able to charge them.
This article suggests an efficient dynamo will cost you up to thirty seconds over 100km when switched off and up to nearly six minutes switched on.
I suppose it depends on how long and where you intend to stop: if charging, I'd think you'll need a better planned and more rigid schedule. A dynamo would give you more freedom to alter your plans on the hoof.
Either way, congratulations on getting a place and props for doing it fixed (you can't back out now)!