unterhausen

I believe you can feel the drag when you turn on a switch to a charger that's hooked up to a partially discharged battery. Not sure I believe that excess drag lasts very long though.

fourfa

My experience with the Son28 and Sinewave Revolution is that the drag is constant no matter the charge state of the device that's plugged in. No device = no drag; yes device = yes drag. No variability over time. It would be nice if it tapered down when devices are full, but unfortunately no. I found it useful to watch battery level on phone and garmin, and disconnect when they were full to save some watts.

Other more complex systems (for instance with switching outputs) may vary...?

Trevtassie

I can't feel any difference in drag, switched on or off. A gentle breeze in the wrong direction makes way more difference...

unterhausen

Is your method of measuring to switch it on and off? It's probably charging up some capacitors every time you do that. Not saying you're wrong, but I have a friend with this setup who is pretty happy with it.

fourfa

Nope, it's based on riding for hours until devices (typically Garmin and phone) have been charged to 100% for some time, then switching it off and feeling the drag instantly reduced. Though it's kinda irrelevant, because as near as I can tell, the change in drag when switching off when devices are fully charged, is the same as the change in drag when devices are actively charging. I'm not a EE, but my guess from observed behavior is the Sinewave isn't smart enough to guess what's happening on the device side, and just pushes full power at all times.

And for what it's worth I'm very happy with the setup - happy enough to equip an additional two bikes with the same hub. It's clear that 5-10 watts is below the threshold of significance for a lot of people. Still, I'm willing to bet that anyone that had a switch on the bars would quickly get in the habit of of switching off whenever they weren't gaining anything (ie going too slow on climbs, and when fully charged). On the other hand the simplicity of just plugging things in and forgetting about it has its own appeal too; I'm sure many would find micromanaging charge states while riding to be more annoying than a little drag.

PS - I get that this is the 'gadgets' sub, not 'touring' so it's worth noting that all my experience with the dyno has been based on multi-month tours, usually riding 6-10 hours a day. If you're reading this wondering about your weekend ride or your half hour commute, none of this really matters. Of course if this were weightweenies or slowtwitch I bet the conversation would be a little different!

unterhausen

I'm a randonneur. In my case, that's a lot like touring, except I'm not smart enough to stop for the night. My mother never did figure out why, if I was going for a 750 mile ride, I wouldn't need a tent.

SafetyThird

Thinking of some longer rides/tours next year, I wanted to experiment with dynamos and phone charging without breaking the bank. I've just picked up a Shimano dynohub complete wheel from Decathlon for £30, which is less than I could buy a hub from anywhere else. I'm sure it's not in the Son or SP class but should give me a chance to do some testing. For charging I've picked up a power bug charger (powerbug . pl) for £28. I have plenty of usb battery packs so will be testing it's ability to charge those on rides this summer.

noglider 

@SafetyThird, let us know how it works out. If you read this whole thread, you will probably see that charging from a dynamo hub isn't economical or practical except if you are far from a power outlet for a long time. Those battery packs are light for the power they provide and are usually a complete solution.

SafetyThird

Will do. For most rides, a battery pack will be fine but I'm looking at doing some cycle touring and camping so wouldn't have access to power for a week or more so ability to have a charged phone, gps, camera etc would be very useful.

SafetyThird

Wheel just arrived so now I just need to check how tight the hub is, I've heard they tend to be a bit overtightened from the factory, and that getting some extra grease in there is a good idea. I have a little grease injector gun for my pedals so that should work.

fietsbob

They? which? standard non dynamo wheels without sealed bearings are adjustable..

How do you plan to tell the difference between magnetic pulse drag and bearing .. cup & cone bearing drag/

Tourist in MSN

NO. DO NOT OPEN THE HUB. The magnets in dynohubs make them feel like the bearings are tight, you probably can not turn the axle by hand without tools and that is normal.

SafetyThird

Everything I've read suggests Shimano hubs are overtightened at the factory. loosening them very slightly reduces the drag. There's posts on a couple of cycling forums about it, let me just find one:

https://forum.cyclinguk.org/viewtopic.php?t=101417 and here https://forum.cyclinguk.org/viewtopic.php?t=105162

SafetyThird

I won't be taking it apart, just adjusting the tension and adding some grease to it, you just loosen the non-generator side which allows the hub to move a couple of mm and you can use a grease gun to squirt some extra grease in there.

fourfa

A lot of the advice on those older threads is about quick-release hubs, where they're meant to have the bearings ever so slightly loose when off the bike, because the QR will squeeze the ends together when closed. It's kind of a hack but one that was accepted for generations.

Now with thru-axles, the bearings ride on the axle with no side load to speak of, and usually they're cartridge bearings with no adjustment possible anyway.

So confirm for us - what is the model number of the hub, and is it quick-release?

SafetyThird

It's a DH-C3000-3N-QR, yes it's a quick release version for my old mountain bike.

unterhausen

I have to admit I wouldn't mess with a new Shimano hub, but I have one that needs to be taken apart and overhauled if it's ever going to be on a bike again.

SafetyThird

I took just a little tension off it and now it does what they describe, there's a small amount of movement halfway through closing the skewer and none when it's closed. I'm leaving it at that for now and riding it

fourfa

Since this seems to be the catch-all dyno thread...

I finally got around to building up his & hers thru-axle dyno wheels for me and my partner, with Son28s. First spin today, with my Forumslader, and watching the battery info tab in the Forumslader app while riding (I think it's well worth the upcharge for the Bluetooth module and the matching app! tons of interesting info). First thing I see is despite the 6V / 3W engraved prominently on the hub, the app reports pulling 6W at 10mph, and 10W at 18mph. Any guesses what kind of conversion efficiency the dynamo offers? Is this actually 20W of drag at the wheel, or 12W, or what? Any clue?

polyphrast

First, those 6V/3W are specified with a constant 12 Ohm load at 15 km/h (~9 mph), second your forumloader is a lot of things, but not a constant load. To my knowledge there are no measurements dealing with dyno hub efficencies when the hub is coupled with a usb charger. But in a (german) bicycle magazine (fahrradzukunft.de), the SON28 was measured with a 24 Ohm load (6W), giving peak efficiencies of 78% at 10 km/h and 70% and 30 km/h (~19 mph). Usually dyno hubs are more efficient at higher loads, and since the forumslader has an IC, which adapts the load to the speed, you probably have at least 75% efficiency at all speeds. So you'll end up with 13-14W mechanical power required for your 10 W, which is still less than the drag induced by a lousy 3 W sidewall dyno (>15W at 20 mph)...
Source https://fahrradzukunft.de/14/neue-nabendynamos-im-test/ (see graphs 17 and 18 and the paragraph below those graphs)

SafetyThird

My power bug arrived from Poland, will get it hooked up in the next few days.

noglider 

@SafetyThird, I haven't heard of the powerbug. I see you can get it on ebay for $48, shipped free from Poland. I look forward to hearing how it works for you. How do you plan to use it?

SafetyThird

I saw it mentioned somewhere else, I don't recall where but it looked quite interesting. You can get it for £29 direct from the maker on their website https://powerbug.pl The page is in polish but google translate takes care of that and the YouTube vids have English soundtracks.

I fitted it today and on the first spin of the wheel my iPhone went ping and started charging. I've not ridden with it but I'm looking forward to trying it out soon.

Mostly I expect I'll use it to charge a battery pack for recharging a phone/camera etc but I'm looking at getting dynamo lights at some point.

fourfa

I was never too happy about throwing this loose in the bottom of my frame bag with all the FOD and crud and liquids that might bounce around in there on tour:


So I came up with this:


Not too pretty, and a couple not-strictly-necessary ounces, but it gives me the warm fuzzies. Nice sturdy start button, a 4-pin aviation connector for quick and secure connection, water-resist 2xUSB on the bottom with a rubber cap. Much nicer to throw in the backpack off the bike as a general-purpose powerbank.

SafetyThird

that looks very professional indeed. Nicely done.