Phone charging from dynamo

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  • Phone charging from dynamo
  • Anyone got any recommendations?

    Just a trickle charge to keep a phone running is all i’m expecting. Running a 6v 3w dynamo and have an exposure dynamo light.

    Must be removable as it’ll probably beswitched between bikes.

    I used a Busch & Müller USB Werk to charge an iPhone and powerpack. Worked fine and seemes a robust piece of kit. Sold it on not long ago as wasn’t cycling enough to justify keeping it. Also found it easy enough to just carry an Anker power-pack when on short camping trips etc, giving 4-5 full charges and supplying led night-light for tent.

    scotroutes
    Member

    A Kemo M-172N will do that for you. Cheap as chips.

    Unless you are out for a few days at a time, a power pack will work better. In fact, I’d buy one anyway, use the Dynamo/Kemo to charge that, then top-up the phone when necessary.

    Kemo now ordered. Thanks

    aP
    Member

    I just use a battery pack charged from the dynamo and top up the phone and Garmin when necessary.

    damascus
    Member

    What Scotroutes said.

    In fact, taking into account the weight of a dynamo and the slight resistance, the cost and the fact it only really works after 12mph I’d use 2 or 3 powerbanks if touring in the UK. Its probably lighter too.

    If touring further a field then I can see the benefit.

    I use a 10000mah pebble, charges my phone 2 times and my garmin 3 times. When ever I stop I always try to plug it in. Less likely someone will steal a battery compared to a phone.

    Premier Icon Bez
    Subscriber

    +1 for using a battery pack unless you’re touring the back of beyond for a week or more. Had a Kemo; it fundamentally works, sort of, assuming your device gets on with a power input that’s constantly switching on and off (not all do), but IMO it’s also a bit crap and not worth the hassle. Bit late now, though 🙂

    scotroutes
    Member

    In fact, taking into account the weight of a dynamo and the slight resistance, the cost and the fact it only really works after 12mph I’d use 2 or 3 powerbanks if touring in the UK. Its probably lighter too.

    I’ve recently built up a new dynamo wheel for my gradventourer but that’s because I like not having to think about lighting.

    Premier Icon cynic-al
    Subscriber

    Weight of dynamo…similar to power bank?

    Resistance… equivalent to 6′ height gain per mile?

    twowheels
    Member

    @cynic-al

    SP PD8 disc weight 390g according to:
    https://www.sjscycles.co.uk/dynamos/sp-dynamo-pd8-disc-front-hub-black-36-hole/

    That >200g heavier than a Pro 4. Also, to get reliable charging I guess you’d at least want a super capacitor along with the rectifier and 5v regulator to smooth out the bumps from the dynamo and in practice likely a small cache battery. Depends how fussy your phone is I suppose. Anyway I reckon a minimal setup would be ~100g more than a 5000mah pack. Do you care? (probably not)

    Agreed resistance would be minimal but I suppose if you’re racing. I used the cheapest Nexus dynamo hub for commuting for years. I could barely notice it.

    Anyway, back to the original question OP if you are handy with a soldering iron you could probably make something for £10 in parts.

    I have an SP dynamo…the 2nd generation one. I used a cheap ‘velocharger’ to charge a power bank and my lights for lots of trips. Its been great. In the Italy Divide, it wasnt always possible to charge for periids at a stop and we were away from power when using bivvi at night. I didnt notice the drag or weight. thoughly recommended.

    whitestone
    Member

    There’s energy loss (roughly 10%) in each transfer from one device/battery to another but in practice unless you’ve loads of devices needing charging it’s not a problem.

    I’ve an SP dynamo (15mm axle version) and at steady touring speeds with eight to nine hours riding a day I can keep a Garmin Oregon and an iPhone going near indefinitely provided I’ve got sensible power saving options turned on – the only time I’ve had trouble is when recharging a camera drained my powerbank and it took a couple of days to get some reserve back. I prefer charging a powerbank during the day and then topping up the devices overnight whilst I’m sleeping.

    Converters vary in efficiency and at the speeds at which they will begin to charge whatever’s connected. I’ve an Igaro and it works down to 8kmh whereas my wife has a Velocharger and she needs to be moving at 12kmh or more for it to begin charging. The good ones are also a little more complicated than a rectifier and smoothing capacitor.

    A lot depends on length of trip, what you expect to be doing in terms of terrain, speed.

    Premier Icon Pawsy_Bear
    Subscriber

    Been traveling for six weeks and I use a battery pack to tide me over between charges. Camp sites, coffee shops, MacDonalds the list is endless where you can charge up. Can’t see why the average touring rider needs a dynamo. Your never more than a quick ride to the next shop, bar, garage in Europe and many other countries. When I crossed South Africa I took a power monkey and solar panel. Superb charging.

    Premier Icon jameso
    Subscriber

    Kemo works well ime, USB Werk is more compact but does same thing. Had the USB Werk a few years and it’s been great.

    Can’t see why the average touring rider needs a dynamo.

    So I don’t need to stop in cafes for any longer than I want to 🙂

    but mainly so I always have lights, but that’s only a benefit if you ride early or late regularly. Did 6 days recently with just a powerbank, was fine but the need for charging at stops was a very minor faff. Half the time I just forget, too busy thinking of food/beer/coffee..

    twowheels
    Member

    Here is some drag testing for SON and SP https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/

    Light Switched ON While Cycling @ 10-30km/h
    Schmidt SONdelux // 2.50w-6.50w drag
    SP Dynamo PV8 // 2.75w-7.00w drag
    Schmidt SON28 // 3.00w-6.50w drag
    Sanyo H27 // 3.75w-7.25w drag
    Shimano DH-3N80 // 3.50w-7.50w drag

    – The most efficient dynamo hubs when switched ON add between 3min 24sec and 5min 47sec to a flat ride over 100km when compared to a regular hub.

    CraigW
    Member

    The Igaro charger looks good. It claims to be more efficient and more stable power supply etc than the others. Not currently available to buy, but a new improved version coming soon. https://www.igaro.com/

    twowheels
    Member

    The Igaro looks well made (in the UK apparently) but tbh £110 seems expensive as I believe you could hack something for ~£10 that can safely and efficiently charge a power bank. The Igaro will still only be using a (good) off the shelf switching regulator. It’s possible they are doing something smart to efficiently deal with the over voltage thing (I note they seem to mandate use of an intermediate battery so perhaps they cut the input from the dynamo when charging current falls too low).

    twowheels
    Member

    I ready more on the Igaro [ ref: https://www.igaro.com/d1 ]. Nice Ti case and they claim 88% efficiency. A decent switching regulator alone already loses 4% so they’re getting AC-DC conversion, voltage protection etc done around 8%, which is OK I suppose. So I can see why people like it but yikes £110 + £110 (min price I’ve seen for the PD8 disc 15mm version) is quite a price to charge your phone 🙂

    whitestone
    Member

    I’m no electronics expert (closer to numpty really) but I assume that most of the converters use pretty much the same kind of circuitry and components. One “homemade” converter is the forumslader and looking at the images of this it looks a little more than a hack.

    I got my Igaro second hand but I’d considered buying it new, I think mine’s the v3 model. TBH, none of the available models are particularly cheap – https://www.spacycles.co.uk/m2b0s208p0/Parts-and-Accessories/Lights-Dynamo-Lighting-Charging-Devices I suppose everyone charges what the market will stand and once someone charges X then if you charge a quarter of that people will think it’s nowhere near as good regardless of the actual performance. I read somewhere that the Igaro needs a sink such as a battery when riding at high speeds for an extended period (long alpine downhills and the like) otherwise it burns out. I don’t know what they claim but as I noted above, mine will supply power at speeds of 8kmh and above whereas my wife’s Velocharger needs at least 12kmh.

    Here’s a page discussing various chargers – https://www.cyclingabout.com/best-dynamo-usb-chargers-bicycle-touring-bikepacking/

    On another forum I promised to check the output of my Igaro at steady touring speeds which I’ve still not done. I suspect it will output around 300-350mAh so ten hours or so to charge the typical 18650 battery.

    twowheels
    Member

    @whitestone – thanks for the interesting link and mentioing the forumslader- I’ll take a look (yeah maybe I was wrong to describe what I had in mind as being a “hack”- it’s more like what could a normal person make with off the shelf chips and a soldering iron). Oh and I suspect you’re being modest about electronics!

    I am no expert either but I think to practically and efficiently deal with the over voltage issue you need some kind of “sink” at some point. I haven’t checked the theoretical efficiency but I was thinking of having a super capacitor buffer that the circuit charges. When the super cap is nearly full (i.e. just before the current drawn drops off) use e.g. a MOSFET to completely cut the input from the dynamo, thereby letting it spin unloaded (so you’re not wasting pedal power). The super cap would continue powering the chip and delivering 5v at a modest current to your device. When the super cap charge falls below 10% (or whatever) it switches the dynamo input back on through the MOSFET. This ensures the circuit is either drawing a modest current or completely off. Sounds easy 🙂 I haven’t calculated the theoretical efficiency of this though (consistently low speed performance would suffer I guess).

    Based on the Igaro page I linked to it seems the circuits/component choice/quality do vary- they claim the “Supernova The Plug 3” just uses a linear regulator for example.

    [Editted for typos]

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