Viewing 23 posts - 1 through 23 (of 23 total)
  • Is there an absolute beginner's guide to dynamo hubs etc.?
  • I’m planning on building up a Singular Rooster 29+ for bikepacking.
    I intend to use my existing lights; Exposure 6 pack with 10 hours on medium setting and Exposure joystick with 3 hours on medium setting.
    I’ve already got a triple piggyback, which can extend either of those.
    I will also use a Garmin 800 with about 15 hours battery life, although I suspect that would be less if I use the live mapping and backlight rather than just a speed & distance display.

    So, I need to charge the Garmin while I’m riding, without it switching itself off.
    On longer rides I will also need to charge one or both lights.
    Is it possible to charge two, or even three items at once?
    At the moment, I’m only planning weekend trips, so maybe the piggyback for the Joystick with the 6 pack on it’s 24hr Low setting and an external battery for the Garmin would do me.
    I like the idea of knowing that everything is being kept charged while I’m riding though, so what do I need?

    Premier Icon scotroutes

    I don’t think you’ll be generating enough power to keep everything charged individually. You’d be best looking at some sort of buffer battery.

    If you don’t have a buffer battery between the dynamo (plus “regulator”) and the Garmin it’ll keep switching into battery mode. This is, apparently, quite annoying. I’m hoping to fool my Oregon 600 into recharging as I ride (it uses AA’s but has a built-in recharge circuit) and it doesn’t seem to have this same annoying feature.

    This whole subject has been done to death on the bearbones forum.

    All the threads I’ve found seem to assume some prior knowledge about buffer batteries and regulators and so on.
    I’m coming in to this as a beginner, so I guess I just want someone to do all the thinking for me and just say, “You need this hub, this regulator, this battery etc and it will all work with your lights and GPS”.

    Premier Icon scotroutes

    Ah yes. Details of power outputs and home-brewed solutions are somewhat over my head too.

    At the moment I’m just using a SP-8 with a Revo light, a Kemo regulator and a Garmin Oregon. I reckon I can get away with no buffer battery as that’s all I’m looking to power. I’ll likely opt for something cheap/small if I decide the mobile phone is important enough 🙂

    Premier Icon jameso

    SP hub > B+M USB-Werk charger > Garmin 800 with Edelux 2 light on my road bike. Works great, the USB-Werk has a very small cache battery so I only get the ‘lost charge’ warning on very long, slow climbs (ie European/Alpine, rare in UK).
    An additional (larger capacity) cache battery would be needed for the Garmin off-road as the speeds are much slower generally. So any AC to USB converter pack (Kemo, B+M, Sinewave etc) and a 2000mah r/c battery would do it. I’d probably want a small USB-charged bar torch for climbing or tricky descents too as most lights won’t put out much at 3-5mph. The K-Lite is impressive in terms of output and really wide, useful beam pattern.

    Thanks, so you’re both using a dedicated dynamo light then.
    I was trying to use what I’ve already got if possible.
    I’ve been reading everything I can find on the subject and it does look like everyone has to improvise in one way or another, buying bits from different places and making up cables etc. I reckon there would be a market if someone like Trout or MTB Batteries could sell a simple full plug in system.

    Anyway, going back to the using what I’ve already got idea, would this work…

    Dynamo to regulator (which one?) with two outputs charging my lights while I’m riding with the lights either on or off.
    Then, after I’ve stopped, using the Smart Charge Port on the Exposure lights to charge my phone and GPS.
    I have no idea if the Smart Charge Port can be used in this way.
    Is there enough battery capacity? Is it the correct voltage with enough amps?
    It sounds like a good idea, no need to buy any more equipment, other than cables and the hub and regulator and it uses the battery that I’ve already got inside the Six Pack.
    Would it work though?

    Premier Icon jameso

    would this work…

    Apart from not knowing about the smart port part, yes. At MTB pace it’ll take maybe 3.5-5hrs to charge a 2000mah battery, takes me 2.5hrs on road at ~15-16mph av using a std 5v/500mah USB regulator output, so you could estimate your pace vs charge rate and storage capacities off that. If you use a Sinewave with 5v/1000mah output (same as a Garmin wall charger) your charge times will be about half that. Much of this is stuff I’ve learned from input on the bearbones site so worth a trawl through there.
    Pretty sure that Mike Hall or maybe Jesse Carlson was using a sixpack running from an SP hub in the TDR last year, certainly it’s been used in that format by someone that knows what they’re doing anyway.

    Premier Icon scotroutes

    MidlandTrailquestsGraham – Member
    Dynamo to regulator (which one?) with two outputs charging my lights while I’m riding with the lights either on or off.

    I guess you’ve tested whether or not the battery in your light will charge and discharge at the same time?

    Good point, Scotroutes.
    The Exposure light will definitely work while charging, unlike a Garmin 800, I’ve tested that, but whether the charger will keep up, I don’t know.
    The Exposure manual quotes 24 hours to fully charge a Six Pack, which is exactly it’s burn time on low setting, so I suppose the best I could hope for is to break even by starting the trip with fully charged lights.

    So, I’m thinking now;
    Start with everything fully charged
    Riding in daylight:- charge phone to keep it topped up. GPS is running down.
    Riding in the dark:- charge lights while they are on to retain battery charge. GPS and phone are running down
    Camped up:- Use light battery to recharge GPS. Phone is running down.
    Sleeping:- Switch phone off.

    Edit to add;
    Second day:- charge lights while riding in daylight

    I won’t know for sure that this works until I actually buy a hub and regulator, but I can simulate it for now by using a wall charger and seeing how many days of commuting it takes before something goes flat.

    Premier Icon scotroutes

    How about
    Riding in daylight:- switch phone off to retain its charge
    Riding in the dark:- keep phone switched off to retain its charge


    That’s an even better plan. If I’m out on the bike I’m unlikely to be able to do anything about any urgent calls, so I might as well just switch the phone on occasionally to see if I’ve got any missed calls or texts.

    Premier Icon scotroutes

    Whatever did we do about urgent calls before mobile phones eh?

    Premier Icon zilog6128

    The Exposure light will definitely work while charging, unlike a Garmin 800

    You definitely can use an 800 whilst charging – I’ve done it – you just can’t use a regular USB cable. I think you need one that doesn’t have the data pins wired up (so the Garmin will accept power but not go into file transfer mode i.e. you can still operate it normally). I have a cable that (I think) came with an external battery and that works fine.

    Premier Icon imn

    As a tangent to the OP’s question, could you use a solar charger during the day? I’ve no experience, but something like Bushnell portable solar charger with 5V/1A output looks like it might help.

    Martin B

    If your anywhere around Cannock, your welcome to have alook at my set up. Similar to some posts above I run a SP PD8 to Revo light, but then I take power through a Plug 111, to power phone GPS etc
    I can talk you through some options and different set ups (Pro’s and Cons)

    Let me know


    Thanks Martin, by coincidence there’s a BMBO event at Cannock this Sunday, but we’re doing the Tandem Club ride at Ledbury, so won’t be there.

    zilog6128, that’s interesting. I searched for information on how to get round this and it seems to be a common question on several forums with people talking about modifying leads and putting resistors in series.
    I’ll get one of these anyway, and see what happens. There’s only two contacts on the plug end, so I’m guessing it might work as yours does.

    What’s the difference between the PD8 and PD8X, apart from the obvious 15mm axle, although there is a 9mm converter available.?
    There’s not that much information on
    The SD8 is only 2.4w, so I’d go for the 3w PD8, but what makes a PD8X worth nearly twice as much?

    Premier Icon scotroutes

    The 8X is supposedly less draggy. I don’t know how noticeable that would be.

    I’m surprised the price difference is so great though, I thought RRP was only 30% or so more. I guess folk are just dumping the old PD8 now.

    It’s a bit of a small picture, but it looks like there’s only 1w in it at 30km/h under load and less than 0.25w with no load.


    CTC forum always good with dynamos.
    Why the fuss with the phone. I assume you are going to be away from home. why not report in, from the pub, every evening? Surely thats plenty.

    Yeah, I’ve realised I was worrying too much about the phone, it’s not really a problem.
    At the moment, I’m only doing local overnighters and what I’ve already got is working fine.
    As I start wandering further afield, the GPS, not the phone or lights, is going to be my electrical limit.
    Hopefully, that lead I linked to above and my Exposure Triple Piggy Back plugged in overnight will charge it up enough for the second day.

    I’m building up a 29+ bike though, mainly for bikepacking, and I need to build a pair of wheels anyway, so it makes sense to future proof it for any multi day rides I might do by using a dynamo hub.

    Martin B

    If your building wheels anyway, it doesnt cost much extra with a SP PD8 hub, and you get loads of options / flexibility

    Let me know when your about as Im quite often over the chase
    had a little bivi trip last weekend and got woken by a rutting stag, chasing a couple of hinds through the trees. Fantastic to get so close to nature, and right on the doorstep 🙂

    Premier Icon composite

    I wrote this blog about my particular set up.
    “Dynamos, Lights & Power On The Trail” –

Viewing 23 posts - 1 through 23 (of 23 total)

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