Just bagged a son delux dynamo hub wheelset. Need help.with how.to wire the thing up for charging. Can anyone help with a.link showing what I need to do and bits needed. Ta

Do you just want to charge stuff from it? Or run a light as well?

If its new then it should come with the connector for the wire, if not you’ll need that, theyre only a couple quid. Pack it with Vaseline or silicone grease to keep moisture out.

If not using a light then you will need some wire. You can get dynamo specific stuff, but really any old scrap wire will do, its only 0.5A.

You then need something to convert it to DC and have a usb socket. And a preferably a cache battery although you can just charge a powerbank during the day and plug your devices into that overnight. Plenty of options ranging from £20 to £150 with various pros and cons like the cache battery and how easy they are to mount/hide.

After all that faff youre missing out on the main benefit of dynamos, namely 24/7/365 lighting that doesnt need batteries and doesnt piss off anyone looking at your bike. The rather snappily named B + M LUMOTEC IQ2 LUXOS U SENSO PLUS puts as much light on the road as my 2000lumen mtb lights, with a 300lumen led, and will charge stuff too.

Basically you need something to convert the AC from the dynamo to more usable (in the case of bike based electronics) DC. This link https://www.cyclingabout.com/best-hub-dynamo-system/ should show you what you need – since you mention charging then it’s the green dotted route you need to follow in the first diagram.

There are lots of converters available each with their own characteristics: some give output at low speeds, others are more suited to higher road speeds. Some replace your stem cap, others just strap to the bike somewhere. Prices vary from £50 to £150.

You’ll see occasional reference to pass-through batteries, these are ones that can be charged whilst simultaneously charging something else. A bit of a mixed bag, the general feeling is that they aren’t as reliable as something like a normal powerbank.

I charge a cache battery through the day then use the charge I’ve accumulated to charge up whatever devices need it at night. There’s a loss in efficiency because of the extra stage but I find it more convenient – Garmin GPSs don’t like the varied output you get when cycling so they keep wanting to shut down when you get to a gate for example!

Don’t expect to be charging up a laptop, at 10-12kmh my system produces 300mAh so a full day’s riding of 10-12hrs will produce enough energy to charge up an 18650 type battery. Have a read of this for real world usage – http://bobwightman.blogspot.com/2018/08/itts-touring-and-powering-electronics.html

Have a look on the SON website. Going back a few years but I think they have details on there.
Look for something called an e-werk which is there A-D converter.
In practical terms its very crude connections to the dynamo and just does not look right exposed to rain and crap but it does just keep working.
Biggest danger is forgetting to disconnect when taking off your front wheel.
This only happens when you have your bike suspended in one hand while you drop the front wheel out with the other and wheel is left dangling on the wires or pulls the faston connector off the wire because no one has the correct crimping tool and just bodges it with some pliers.
This is the voice of experience.

Cheers, looking at doing the French divide with a mate in 2021 as we’re both 50. It would be for charging a battery to top.up garmin or phone etc.

How long are you going to go between access to mains power?

I’d consider something like a 20,000MAh battery pack fully charged at the start of the ride (you can get an Anker one for under £30 on Amazon, I’ve always found Anker stuff to be excellent).

If you’re riding off-road and mainly in the light then a dynamo may not be ideal: most dynamo-powered lights have road-specific beams which actually aren’t so good off-road, and they’ll tend to flicker at low speeds, which becomes a real issue on off-road climbs. There are some lights designed for off-road (eg Exposure, Supernova, Sinewave, the last of which will also provide USB output), but they’re expensive.

If you’re going for dynamo lighting then a Luxos U or a Sinewave is probably your best bet, but even then I’d charge a (smaller) battery pack rather than directly charge devices. You could even have two small packs if necessary: one charging from the light while the other charges a device.

But it all comes back to that first question; you may be overthinking it and it may just be easier (and a lot cheaper) to carry a battery.

I’d read that blog linked above, so true.
I did a 500km ride in Wales, gravel and road with 10000m climbing, on a road bike with a dynamo. I battled to keep things charged. Admittedly I used my phone for pics and social media updates, but the slow climbing speeds didn’t allow for charging. Then the descents which were fast, were not long enough before another climb started.

In the valleys and flat sections it works great, but in mountainous terrain, I’d rather take a powerbank that allows for rapid charging from a plug point. The USB-C ones allow for that.

Remember, the larger your wheel & tire combo, the slower the hub will spin. For that reason, I have not fitted one to my Fargo with 29 x 3″.

@turneround – I got the dynamo setup mentioned in my blog for the French Divide (I’ve a SON on my commuter as well). Like all ITTs (I’m assuming you are going for the group start) you can use “facilities” where you find them so charging up a battery whilst having a meal at a café is acceptable and given the French attitude to cyclists you probably just need to ask.

@Bez – he already has the dynamo wheel so it’s not a future cost. On last year’s FD it was roughly 60-40 between riders with dynamo and battery only. The northern part of the FD is a mixture of roads and tracks and is fast – I did 270km in around 16hrs including all my stops on the first day for example – so charging from dynamo is perfectly feasible. I just used an Exposure Joystick mounted on my helmet for lighting – by the time it gets dark you’ll have been riding for at least twelve hours so you aren’t going fast. A couple of hours per night on one of the low settings is likely usage.

Electrical priorities in order are:
GPS
phone
lights
camera

With GPS being way more important than the others. Using a Garmin Oregon with all power saving settings turned on and not looking at the map every minute or so will last a full day’s riding. Charging that overnight uses about 1/3 of the charge in a 10,000mAh powerbank. Plugging the powerbank into the dynamo would recharge it with the following day’s riding. Then repeat.

Phone would be in airplane mode until I needed it. You’ll get several days’ usage like this.

A couple of 10,000mAh batteries would be more than enough. 2×10 is better than 1×20 since you’ve a bit of redundancy should one fail. I managed two weeks’ riding using just one. Charging them, even intermittently, on more technical terrain will delay the point at which you need to find a mains charger.

One non-electrical tip for the FD: make sure that you can load and see all the individual GPX files. Quite a few riders last year got to segment 4 or wherever and the file would refuse to load or display but that very same file would work on an identical unit. I don’t think anyone found the reason why this happened.

Thanks guys, great advice there.

Just a thought, I’ve not tried it, but dynamos are a constant current source, i.e. for a given rotational speed they will output a given current (approximately*) regardless of the load. So at the nominal speed they output 0.5A, 6V through a light with ~12ohm resistance. You plug two lights in series it will output 0.5A 12V and be twice as hard to turn, you attach no lights at all and the voltage ramps up to something silly like 70-150V.

So if you want to charge stuff quicker, then get two cheap chargers and wire them in series?

*a bit like the opposite of a battery which is approximately constant voltage. It’s not completely constant but it doesn’t halve when you double the resistance, more like 9/10’ths.

Hmm, not sure about that (My electronics isn’t brilliant), but you need an AC/DC converter in the circuit and I think those limit the output, usually to the USB standard of 6V and 0.5A. The lights that attach directly do something similar to avoid being burnt out when freewheeling down long descents.

Hmm, not sure about that (My electronics isn’t brilliant), but you need an AC/DC converter in the circuit and I think those limit the output, usually to the USB standard of 6V and 0.5A. The lights that attach directly do something similar to avoid being burnt out when freewheeling down long descents.

Yes, but in theory you could just run two USB converters, either to two cache batteries, or some have dual usb inputs for faster charging.

I had an idea for a setup, if you measured the frequency at say 20mph (i.e. road descents) then built a rectifier that would sense that frequency and only switch on at high speeds, then charge a cache at say 20W which could then be used to charge your devices. Efficiency would become less important at higher speeds the loss in speed for a given power is lower. e.g. if 100W = 10mph, then 400W (100W pedaling + 300W of gravity) = 20mph. But 80W is 1mph slower on the flat, and 380W is only 0.5mph slower and any drag fron the dynamo is offset against braking less anyway.

This is exactly how I built my dynamo light. 3 X-ML LEDs. 2 come on at low speed, above 14kph the third one turns on.
You are correct that it’s constant current, but the load will drag the voltage down if you are not going fast enough. Voltage is needed to ‘push’ the current. You could use a switch mode power supply to charge batteries at a higher rate when going fast.
I used a Traco 5v 1A SMPS to supply my USB out.

@Piesoup please can you share the circuit design for that light? Sounds good.

To get really geeky, you need to be able to match the load to the dynamo. The inductive resistance of the windings determine the power output in relation to speed.
Whatever happens, you are unlikely to get over 4w from a dynamo, regardless of your max speed.
I have not matched my load to the dynamo! It just works. Provides more light that I need at night, and keeps my Garmin powered all day. Keeps my phone topped up if I do not use it too much.

@supersessions9-2 Certainly! You are in luck as I have a few circuit boards left over. No components though

Whatever happens, you are unlikely to get over 4w from a dynamo, regardless of your max speed.

Back of a fag packet, but at ~100lumen/watt the Revo must generate about 8W at 17mph unless my efficiency figure is way out. Though suppose as it’s a dynamo/light bundle they can do more clever stuff in matching the load to they dynamo to maximize the power generated.

This is exactly how I built my dynamo light. 3 X-ML LEDs. 2 come on at low speed, above 14kph the third one turns on.

How does it measure speed, or is it measuring the voltage?

I suppose one way would be to make a circuit act like the MPPT on a solar panel, constantly tweeking the impedance to maximize (or generate a fixed) output power.

Discussion with circuit designer

Here is a link to the forum where I worked through the light.
I have an EasyEDA account with the schematics, so if you want to build it, it’s worth getting an account (it’s free) so I can share the files with you.

Back of a fag packet, but at ~100lumen/watt the Revo must generate about 8W at 17mph unless my efficiency figure is way out. Though suppose as it’s a dynamo/light bundle they can do more clever stuff in matching the load to they dynamo to maximize the power generated.

Yes I reckon they have invested a lot into theirs! My info was a few years old. The XP-G LEDs that are in the Revo are capable of 200 lm/watt. And that’s at 350mA, most likely the output of the dynamo. Amazing little things! So that goes back to 4w to give 800 lumens.

All about dynamos and charging

How does it measure speed, or is it measuring the voltage?

I suppose one way would be to make a circuit act like the MPPT on a solar panel, constantly tweeking the impedance to maximize (or generate a fixed) output power.

Yup, a dual monostable multivibrator was used. It switched a third LED in at a certain speed. If I tried this a too low a speed, there was flickering. A few test runs up and down the raod a night was needed to find the sweet spot.

Yup, a dual monostable multivibrator was used.

Do I get that from RS or Pornhub?

Another option is K lite if you don’t want to build your own. I did that same ride as Piesoup, and have done SDW, multi day road rides etc. using a K lite Bikepacker, a Sinewave revolution and a small pass through cache battery to keep a phone and eTrex charged and always have enough power. For shorter trips at lower average speeds with no night riding a big power bank would be my choice though.

https://www.kliteusa.net/kliteusaproducts

Also look at the Igaro D2. It claims to be more efficient and more power output than others. https://www.igaro.com/d2

@supersessions9-2 Certainly! You are in luck as I have a few circuit boards left over. No components though

That sounds great, thanks. Can it be built without the usb charge aspect? I’m only interested in the light and I want the automatic switching of extra lights at speed. This is for road commuting

I went from a home build twin led with super cap standlight to a busch and Muller cyo premium.

I like the reflector on the b&m but can’t help thinking it could be brighter at speed.

My home build was great for light spread and side visibility but lacked brightness for unlit damp roads at speed.

I was thinking of taking a b and m reflector and custom fitting multiple led with the option of a speed sensitive boost.

Yes, that light is just the light. It’s plenty bright!
One thing though, buy genuine CREE LEDs, the cheaper ones from the Far East didn’t behave probably.

What is it that makes these dynamo USB chargers quite so expensive? You can convert just about everything else into regulated 5V for a few quid so I was surprised to see the cost of these things.

I was thinking of taking a b and m reflector and custom fitting multiple led with the option of a speed sensitive boost.

Isn’t the issue there that reflector-style lights need the LED(s) to be in exactly the right place, so switching LEDs on and off will alter the beam shape?

What is it that makes these dynamo USB chargers quite so expensive? You can convert just about everything else into regulated 5V for a few quid so I was surprised to see the cost of these things.

Dunno exactly: Most other converters have a reasonably steady input so converting isn’t that big a deal whereas dynamos can be anything. Wanting/needing to make a profit from low production runs will come into it as well.

I made a usb charger with an ldo regulator, bridge rectifier and a few smoothing caps. Only cost a few quid. Seems to work fine although don’t use it much.

I suspect packaging and trying to make a profit on small volumes is probably why they are so expensive.

What is it that makes these dynamo USB chargers quite so expensive?

It’s a surprisingly tricky problem. Devices that charge over USB assume a steady power input, and react badly to fluctuations. Eg, phones generally expect a solid 1A at 5v, and even if your regulator can keep the 5v at lower speeds, the current will drop, with very unpredictable results. Also, 1A at 5v = 5w, which is most of the power a dynohub can output, and needs fairly high speed to do so, and lighting can’t be used at the same time. Solutions to all of this can be complex – a cache battery, speed sensing, lighting control, etc. The finished unit needs to be sealed and waterproof, which calls for expensive connectors. The market for this product is also very small, and apparently mostly consists of tight-fisted hairy old cyclists 😉