Dynamo light and charger insight

I've run them for more than a decade. I need to do an update on my setup in another thread.
Personally when touring I always take lights - I've had several occasions when transport delays and other problems have led me to be riding in the dark unplanned. Generally this is a dynamo.

The problem with charging phones directly (main tourer has an Axa Luxx lamp with a USB charge socket on the side) is that the start-stop nature of charging (e.g. junctions, slowing etc) causes the phone to helpfully light up and say it's charging. This often consumes more power than the charge rate, depending on how daft the phone design.

So, it's best to charge a cache battery pack, then use it to recharge the phone in one big go. It also allows other things like GPS etc to be charged. It's up to you whether you then go the whole hog and use USB lights charging off the pack too.

Personally, for lights I am 100% satisfied by the B&M IQ+ on my road bike, paired with an SP dyno. I rode the Dunwich Dynamo in the summer and having zero lighting range anxiety was reassuring. The light has a good low wide beam spread.

For USB charging you can buy some like the https://www.sjscycles.co.uk/dynamos/klite-micro-usb-charger-box-type/ which aren't that cheap, or use a home-made circuit (plenty on the internet). Typically they use the 7805 regulator IC which is not great on efficiency but simple and does the job. There are also eBay converter modules for around £10 like https://www.ebay.co.uk/itm/12671362...044&customid=a5f753adf3d317db3a583483e76d9e49
I will get round to trying them soon.

Here is an old but pretty good article. https://www.cyclingabout.com/best-dynamo-usb-chargers-bicycle-touring-bikepacking/

There is also a lot on the Cycling UK forum.
 
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Thanks @hamster, that’s useful real world insight. Other commentators I’ve been coming across also highlight the merits of the charge a powerbank approach.

I’ve been looking at drag data (🤦‍♂️) but it’s all relatives: how noticeable is Dynamo drag in day today riding?
 
Thanks @hamster, that’s useful real world insight. Other commentators I’ve been coming across also highlight the merits of the charge a powerbank approach.

I’ve been looking at drag data (🤦‍♂️) but it’s all relatives: how noticeable is Dynamo drag in day today riding?
Frankly I never noticed a difference. It’s less than the difference between a clean or dirty chain, or tyre pressure.
 
for anyone reading and thinking of using older dynamos - they were alternating current so some sort of rectifier was needed for a DC output to charge something

modern hubs should have that all built in
They do not. The standard output is 6V 3W from the hub connectors P24. All the electronic are built into the lights. You can verify this by wiring any simple bulb straight to the outputs. It flickers at slow speeds and appears constant as you go faster, the frequency being wheel rpm/poles pairs.
This can be gotten rid of with stand light circuits, the simplest of which is a bridge rectifier and a super cap. If you do this, be careful with grouding to the frame

There is a bit on charging in that doc too (p6) and a varity of special cables to make the process simpler.

6V AC might put something into your phone, but not a lot and it might fry something too. A simple brige rectifier would probably work since the RMS of 6V AC isn't too far off 5VDC (USB voltage). It probably isn't too hard to make a simple circuit for this if you're electrically savy - Start here. but your decives might be expensive. Again be careful with grounds if you're using the frame as a return, shorting the hub will act as a brake until it burns out.
 
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All dynamos are misnamed and in fact alternators, as @gilmo789 says.

That DIY charger uses a linear regulator which isn't great on efficiency. I'd also want to heatsink it. The ebay modules use some kind of switch mode or flyback converter which are much more efficient. I'll report back on the one I've ordered as an experiment.
 
Well bugger me. One would have expected "technology" to have moved on with the humble dynamo.
Those yellow and black bicycles from that failed OFO bike rental lot are rumoured to have built in usb chargers
 
Well bugger me. One would have expected "technology" to have moved on with the humble dynamo.
Those yellow and black bicycles from that failed OFO bike rental lot are rumoured to have built in usb chargers
If they have some electronics like GPS or app release functionality, there will already be a rectifier somewhere. Not having see them I can only speculate
 
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