Help: Building a bicycle power system circuit DIY

Discussion in 'The Projects Forum' started by hargisbb, Feb 12, 2016.

  1. hargisbb

    Thread Starter New Member

    Feb 12, 2016
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    Hello,

    This is my first time in this forum but it seems to be the right place for expert advice.

    (I will try to be brief but detailed)
    I am building a long-term touring bicycle that I will be living on for years. (a whole other story). The long and short of it is, I need to charge electronics, like professional camera batteries, devices, phones, laptops, etc. while being out in the sticks far from reliable power sources.

    I have limited knowledge of circuits but enough to grapple with concepts and I built a few basic circuits years ago in college courses. So, I have an idea of what I need but cannot connect the dots to build the actual circuit.

    I will have two power sources, solar and dynamo, but by nature they are fluctuating in output. Therefore, I want some power storage in the form of a substantial battery pack to charge devices with in the evening as well as redistribute my power to multiple devices at once.(I don't want to be stopping all the time to check if something is charged off a single port and can be swapped out for another device) FullSizeRender.jpg FullSizeRender.jpg

    I am aiming for the system to be rather hands free once it is assembled. In other words, the lights are auto engaging with daylight(they may already have this feature). Additionally, though power input fluctuates it is all neatly managed by the batteries and provides a steady output of charging and ideally, in the end, I would like to be able to disconnect the solar and battery case to take them inside the tent for the night.

    I'll attach a drawing of the system I am envisioning. It all rides on the cycle.
    Thanks everyone. I hope I can make this concept into more of a reality.
     
  2. hargisbb

    Thread Starter New Member

    Feb 12, 2016
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    Sorry the image upload repeated and inserted itself in the middle of the post.
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Your hub dyanamo will give out 6V DC at 3W @65% efficiency at 15Km/h, your lights take 3W each, thats not much use at night if your wanting to charge a 5V usb device, you need to be charging in daylight.
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    That could add up to a pretty significant energy requirement. Assuming the laptop alone needs 60W and is used for only one hour per day, with a 3W dynamo you'd have to be pedalling 20 hrs just to replenish its battery that way. Solar power sounds promising, but have you checked the spec of panels to see just how big a one you'd need for it to be useful?
     
  5. ian field

    Distinguished Member

    Oct 27, 2012
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    The generator is more or less a current source, so you can stabilise it at a higher voltage and not get all that much less current - the net effect should be an increase in power output. Its all in the greater scheme of things so you can pedal furiously downhill without blowing the bulbs.

    Let the dynamo voltage flourish and convert it down with a buck regulator.
     
  6. wayneh

    Expert

    Sep 9, 2010
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    I'm skeptical that you'll be able to make this work in the way you imagine, unless you can use a large panel while riding. This project should start with an energy audit: you need to know just how much power you need. Then realize that there will be losses in battery storage and voltage conversions. I'd use a factor of two, so for instance if you need 2kWhrs per day, you need a source that can produce twice that much. Then add a buffer for rainy days.

    Once you add it all up, I think you'll find that the dynamo, while useful, will be a trivial source and that the panel you need may be impractical on a bike.
     
    Evanguy likes this.
  7. hargisbb

    Thread Starter New Member

    Feb 12, 2016
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    Thanks for the help everyone. So, to clarify my aims and problems.
    • I realise that from an ideal power output situation I am not in the best of situations. I will never be able to catch up my power needs if I had the demand of recharging everything all the time.
    • Unfortunately, my priorities as a cyclist are more in weight and efficiency so I have to take the good with the bad and be ok with what power output I can hope to achieve.
    • I failed to mention, I will be able to duplicate this system across two bikes, my partner's as well, which will help.
    • ***Additionally, I know that I will never be able to charge up everything off this set-up but I will, hopefully, be around plugs and civilisation every 5-7 days. So this is a maintenance system to top up or recharge the occasional battery, not a full recharge of everything.


    The lights will more often than not, not be in use. When cycle touring, I plan to be in camp before night most days. Once the system switches to powering the lights, I do not expect to get much if any additional power output.

    Thanks for the estimates on that power need. What are some good places to source decent quality but reasonably sized solar panels? I am not opposed to building up a durable portable style one myself to gain higher power inputs into the system.


    I need to look the specs up in more detail but I think this dynamo has power output regulations in place? Son is the top dog in the cycle dynamo industry right now and blowing bulbs is a thing of the past, if you invest upfront. But the reputation can persist and I still see way to many questionable dynamos here in Japan that run on an incandescent bulb and look ready to blow at any moment.

    To go further on your point though, as you pointed out the dynamo is a decently steady power source, by cycle standards at least, but it won't be utilised for lights during most of the day so that's why I am shooting to aim that power to a storage bank and redistribute it as needed to other devices.


    Thanks for the input. I need to get more expert takes like that on the set-up. I guess I am approaching this from the opposite direction. I know I will never be in an ideal output to input situation, unless I tow behind a solar panel on a trailer, which is way too complicated. I am shooting to see how much I can get out of this setup, utilising the dynamo and best possible solar panels without being cumbersomely big. With those numbers in hand, I can decide what are my limitations in time away from power sources, how much I can use my electronics, and how many spare batteries I may need to carry. This system's aim is to off-set some of the usage and make me a little more self-sustained than carrying pounds of batteries and searching for power outlets like water sources in the apocalypse, ;)

    Thanks everyone. So to get back to my original aims. Is there a feasible way of linking this set-up together into a circuit? I want to build the board and batteries into a pelican case that can ride but detach from the rear rack. That way, hopefully, I can top up a decent sized battery pack during the day and recharge anything that might need a little juice in the evening.
     
  8. Evanguy

    Member

    Dec 21, 2014
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    If it was me i forget all the charging stuff and bring a small 600-900w generator either in a trailer or on a back rack and maybe a liter of gas. then at your camp sites fire it up and charge your stuff. also they are pretty light and small nowadays.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    One place to start would be with a charge controller IC for your chosen battery. You won't know what, if anything, you need to do with the incoming power sources until you see what your charger can accept. The absolute simplest way to "OR" power supplies together is to put a blocking diode in series with each one.
     
  10. hargisbb

    Thread Starter New Member

    Feb 12, 2016
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    What about something similar to this http://www.voltaicsystems.com/17-watt-kit. My only question for the manufacturer, unless someone can deduce from the specs, is whether you can also charge the battery via dynamo while charging with solar? This is more along the lines of what I am looking for.

    Generators are not a bad idea but from my searches, way to big for anything I would want to lug.
     
  11. Evanguy

    Member

    Dec 21, 2014
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    Last edited: Feb 13, 2016
  12. hargisbb

    Thread Starter New Member

    Feb 12, 2016
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    Thanks, I think I have decided to build a solar set-up out of marine grade panels. That is the smallest generator I have seen but 21 pounds, not including fuel, still weighs more than most of my camping kit combined.
     
  13. KJ6EAD

    Senior Member

    Apr 30, 2011
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    absf likes this.
  14. wayneh

    Expert

    Sep 9, 2010
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    The panels you choose may very well have the blocking diode built in. If your dynamo does also, you can just wire them in parallel. You'll still need a charger to care for the battery. Nicad and lead-acid are more forgiving, but anything else needs care.

    Once you have the battery defined, powering your loads will be the easy part. You may need a DC-DC converter, but those are cheap and very efficient these days.
     
  15. hargisbb

    Thread Starter New Member

    Feb 12, 2016
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    That's really interesting, I will have to look into it more. Thanks
     
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