Dynamo power for USB

microcord

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Aug 28, 2012
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Tokyo
#1
I have a dynamo hub. I've never used the dynamo. I have a USB powered front light and various USB powered gewgaws. I think I should buy a (USB powered, I believe) Garmin thingy. Surely the dynamo should be able to power the USB stuff.

This "List of Hub Dynamo Power Supplies for USB Devices" (put together in Australia in early 2012) shows a number of options. They're from companies I haven't heard of (suggesting that obtaining replacement parts could be difficult), they're expensive, and some look poorly designed.

Cat Eye makes things that need powering, but seems to stay clear of the powering itself. I see nothing at either of two branches of Y's. The one randonneur-oriented shop I've been to (Hasegawa) is delightful but (because?) it doesn't seem to acknowledge any technology postdating 1970 or so. Any recommendations for devices or shops?
 

microcord

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Aug 28, 2012
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Tokyo
#3
I've got something similar myself (though mine doesn't look like a sex toy). But it's one more thing that I have to remember to charge up in advance. And I do have the hub.

Mr Hasegawa looked at my dynamo hub with (I think) polite disdain. "This is how we do things here," he said, showing me a "bottle" dynamo. No thanks! The best I've heard about them is that these days they're not all as bad as they're reputed to be.
 

Musashi13

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Aug 27, 2012
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Ichikawa, Chiba
#5
I have had my Garmin 800 last as long as I have needed it on several all day rides. Similarly, over 8 hours on the move over 12 from leaving to returning home. I was surprised the first time but now take it for granted. When I go to upload the data it has never told me there is less than 10% left in it, how accurate that is I have no idea but I haven't had it run out of juice so far.

My iphone, on the other hand, I now have to keep off until I need it. 3 years old and the battery can't hold a charge for half a day's use (or not use, just sitting in my pocket). I bought a replacement battery and changed it myself but the replacement wouldn't take any charge so I changed it back:(.
 

GSAstuto

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Oct 11, 2009
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tokyo
www.roadfixie.com
#6
Joe has tested this extensively. I'm sure when he's back online he'll be able to give some really great advise. The key component is a power adapter / buffer so that you can charge / power multiple or single devices as required. We tried one variation of this called 'The Plug' which fit nicely into the stem top cap - however it suffered alot of reliability issues.

Here's a list of many of the popular USB charging units. The DAHON version looks quite appealing to me..

http://cyclingabout.com/index.php/2012/03/list-of-hub-dynamo-power-supplies-for-usb-devices/


I have a dynamo hub. I've never used the dynamo. I have a USB powered front light and various USB powered gewgaws. I think I should buy a (USB powered, I believe) Garmin thingy. Surely the dynamo should be able to power the USB stuff.

This "List of Hub Dynamo Power Supplies for USB Devices" (put together in Australia in early 2012) shows a number of options. They're from companies I haven't heard of (suggesting that obtaining replacement parts could be difficult), they're expensive, and some look poorly designed.

Cat Eye makes things that need powering, but seems to stay clear of the powering itself. I see nothing at either of two branches of Y's. The one randonneur-oriented shop I've been to (Hasegawa) is delightful but (because?) it doesn't seem to acknowledge any technology postdating 1970 or so. Any recommendations for devices or shops?
 

StuInTokyo

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Dec 3, 2010
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#7
I'll not speak for Joe, but I can relate some of the testing that Joe and I have done, basically the best situation is to have a buffer battery, and have the hub charge that, then have various devices charge off of the buffer battery. One basic reason for this is that if you go directly to say an iPhone from the hub, (though a power adapter) each time you stop and start the iPhone will wake up as the charging begins, this will suck more power than you are gaining as the screen lights up.
Joe and I have an adapter built by someone that Joe is in contact with from Germany.

Cheers!
 

joewein

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Oct 25, 2011
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joewein.net
#8
Currently I only use the dynamo for the headlight. It draws a lot more power than a Garmin or a smartphone and it's safety critical at night, so not having to worry about batteries is more important than with a GPS logger, where you may just end up losing data for Strava.

In 2012 I tested three dynamo USB adapters from two different suppliers in Germany, but had problems with both on high speed descents. Not only did this kill all the adapters, but it also damaged the devices connected at the time (a USB battery, a smartphone), which must never happen.

Basically the adapters weren't adequately protected against high voltages from the dynamo at high wheel RPMs with the headlight off. In my case this was probably compounded by the fact that my wheels are 25% smaller than 700C. Still, the adapter I burnt out on the Sagamiko side of Otarumi toge at about 55 km/h with 20" wheels probably would have been fried on a 73 km/h descent with 700C wheels.

I don't know how speed-proof other adapters by other suppliers are. Switching the light on for descents should protect the adapter in most cases, as it draws enough power to prevent voltage spikes. Nevertheless, if the adapter doesn't cope with high speeds and you have an expensive iPhone or Android hooked up, it could be rather costly forgetting to switch the light on for the descent...

As for the start/stop issue: yes, a buffer battery is a must, at least around populated areas. Without it the device keeps waking up every time you stop at a traffic light and a second time when you start moving again. After each change of power event the screen tends to stay lit for 30 seconds to 1 minute. Unless a buffer battery covers for those traffic light stops, you may burn through the device's internal battery charge quicker than you replenish it in between traffic lights, simply because the screen ends up being lit too much of the time.

I have not tested any of the following products yet:
  • The PedalPower+ adapter comes standard with a user replaceable 18650 buffer battery. That's a great idea because 18650 cells are generic and relatively easy to find.
  • The Busch & Mueller "USB-Werk" (EUR 99) also comes with a small built-in buffer battery.
  • For the Busch & Mueller "E-Werk" (EUR 147) a buffer battery comes as an option (EUR 74). I find the E-Werk / buffer combo a little pricey for what it does.
  • The Busch & Mueller Lumotec IQ2 Luxos U (EUR 150 at Bike24.de) is an interesting combination of a dynamo headlight with a USB adapter with builtin buffer battery. If I were to equip my bike from scratch right now, I would give this one a try.
The simplest and safest solution of course is a USB battery. It will never generate over-voltages, is relatively cheap to replace if it dies and not that much heavier (if at all) than a USB adapter. I ran both my Samsung Galaxy S3 LTE and my Garmin Edge 500 on a single USB battery during the 25 hour, 360 km Fuji brevet weekend. On its own the Galaxy S3 LTE lasts 6 hours, the Garmin 16 hours while GPS logging.
 

microcord

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Aug 28, 2012
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#10
Thank you all for comments. The risk of overcharging hadn't occurred to me. Yes, I'd be mighty annoyed if any device fried any other device.

The Busch & Mueller Lumotec IQ2 Luxos U (EUR 150 at Bike24.de) is an interesting combination of a dynamo headlight with a USB adapter with builtin buffer battery. If I were to equip my bike from scratch right now, I would give this one a try.
Here it is within bike24.de, and here it is at starbike.com. But this stuff is expensive, isn't it? Yes, I already have a battery (rated at 3000mAh) for charging USB devices, and it's small and light; perhaps I'll continue to use it.

I'm rather irritated with myself for having bought a USB-recharged "Owltech" front light, which slots into a fiddly rubber strap that I imagine will soon perish or snap. I hurriedly bought it at LBS because I was thinking of buying something like it and he'd just wasted 20 minutes of his life on me; I assumed that elsewhere I'd be able to buy an alternative and better Owltech attachment strap. Well, no: this rubber strap is all that Owltech markets. I like Cat Eye, with its array of alternative attachments and replacement tiny bits.
 
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jdd

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Jul 26, 2008
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#11
T...
I'm rather irritated with myself for having bought a USB-recharged "Owltech" front light, which slots into a fiddly rubber strap that I imagine will soon perish or snap. I hurriedly bought it at LBS because I was thinking of buying something like it and he'd just wasted 20 minutes of his life on me; I assumed that elsewhere I'd be able to buy an alternative and better Owltech attachment strap. Well, no: this rubber strap is all that Owltech markets. I like Cat Eye, with its array of alternative attachments and replacement tiny bits.
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