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  1. #1
    Senior Member robert schlatte's Avatar
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    Dynamo hub charging question

    I have a Shimano 3n-72 dynamo hub and I have a LightCharge USB charger so I can charge an external battery pack. When I took off on a recent trip, my battery pack showed three out of five bars of charge. I hooked it up to the charger and rode for approximately 5 hours. The battery indicated that it was charging as I rode (bars lighting sequentially as I rode) but at the end of the 5 hours the battery still only showed three bars. When I got home I connected the battery to a USB port on my computer and the next morning the battery was fully charged.

    My question is, from what I have described, does it appear that my battery charging while on my bike ride? Is the output of a dynamo low so that it takes a long time to charge a battery? Anyone have any experience here? I am going on a long bike tour in the next couple weeks and I want to be able to keep the battery charged up. Any advice or thoughts are appreciated.

    I have posted this in electronics as well.

  2. #2
    coprolite fietsbob's Avatar
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    it is a trickle charge.. know anyone that can measure the output with the multimeter to see what the values of Your system actually is putting out?

    3 bars on an indicator is not real data .. volts ohms amps is the units of measure in this case..

    USB - Wikipedia, the free encyclopedia

    USB.org - About USB-IF

  3. #3
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    I have nothing definitive to offer. But in case it helps here's what I see with my dyno.

    I have a HUB SHIMANO ALFINE DYNO 36H BLACK DISC dyno. I used to use it to charge a POWER CONVERTER PEDALPOWER+ W/ iCABLE AND V4i BATTERY battery pack. On that particular battery pack it would flash indicating a charge. But I'm pretty sure that it was not really charging, or not charging significantly. When my cycle speed increased from say, 5 or so mph to around 12 mph, it would start glowing steady instead of flashing.

    That arrangement worked OK for a while. But I've since starting using a Mophie Juicepak Pro as my battery pack. This holds about 4-5 charges of my iphone. The Juicepak indicates charges with four bars. That's not very accurate but it's workable for me. The juicepak, unlike the iCable, always flashes - never glows steady. On average it will go up something less than two bars or so in a day of riding.

  4. #4
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    I did this write-up a few days ago that may be on interest.

    Review: Charging gadgets from SONdelux and Sinewave Revolution.

    I tested two different battery packs with my dynamo. One would not accept a charge at all. As mentioned above, the best way is to answer your questions is to measure the actual output. You can buy USB "power meters" to do this, but the easiest way, if you have some basic electrical skills would be to measure with a multimeter.

    What's the capacity of the battery pack? (mAh) Keep in mind that if it's a large pack, it may take a long time to charge with a dynamo.

  5. #5
    Senior Member robert schlatte's Avatar
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    Quote Originally Posted by Jonnythecanuck View Post
    I did this write-up a few days ago that may be on interest.

    Review: Charging gadgets from SONdelux and Sinewave Revolution.

    I tested two different battery packs with my dynamo. One would not accept a charge at all. As mentioned above, the best way is to answer your questions is to measure the actual output. You can buy USB "power meters" to do this, but the easiest way, if you have some basic electrical skills would be to measure with a multimeter.

    What's the capacity of the battery pack? (mAh) Keep in mind that if it's a large pack, it may take a long time to charge with a dynamo.
    After I posted I did see your post. Thanks. I think that I just need to know it is charging regardless of how long it takes. I think reading everything makes me feel it is working.

  6. #6
    Senior Member robert schlatte's Avatar
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    Quote Originally Posted by Jonnythecanuck View Post
    I did this write-up a few days ago that may be on interest.

    Review: Charging gadgets from SONdelux and Sinewave Revolution.

    I tested two different battery packs with my dynamo. One would not accept a charge at all. As mentioned above, the best way is to answer your questions is to measure the actual output. You can buy USB "power meters" to do this, but the easiest way, if you have some basic electrical skills would be to measure with a multimeter.

    What's the capacity of the battery pack? (mAh) Keep in mind that if it's a large pack, it may take a long time to charge with a dynamo.
    Thanks for your response from over a year ago. I am still trying to make my lightcharge device work for touring. This morning I hooked the device up to my hub and to my battery pack and the light bars lit up sequentially just like it was charging. The battery is a Rosewill lithium polymer with a capacity of 7800mAh. The instructions say it takes 15.6 hours or more depending on the charging source. From reading your previous posts, it looks like I would need a measuring device such as a multimeter to measure the battery's output to determine if the battery is accepting a charge from the dynamo charge via my USB charging device?

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    If you just want to make sure it's charging at all, run it dead, plug in to the bike to charge, and go for a long ride. If it's still completely dead, it's not charging. If it's only Mostly dead, it's just charging slowly.
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    Quote Originally Posted by scyclops View Post
    Oh yeah, sure, what if everyone thought that way? Then internet forums would merely be places where rational people exchange useful information and ideas - instead of the chaotic, emotionally-charged circuses that they are.

  8. #8
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    Quote Originally Posted by Jonnythecanuck View Post
    I did this write-up a few days ago that may be on interest.

    Review: Charging gadgets from SONdelux and Sinewave Revolution.

    I tested two different battery packs with my dynamo. One would not accept a charge at all. As mentioned above, the best way is to answer your questions is to measure the actual output. You can buy USB "power meters" to do this, but the easiest way, if you have some basic electrical skills would be to measure with a multimeter.

    What's the capacity of the battery pack? (mAh) Keep in mind that if it's a large pack, it may take a long time to charge with a dynamo.
    After looking at the above post, I wondered how easy it is to buy a cheap amp and volt meter with USB plug and jack so I would not have to assmble one myself. I did a quick ebay search and found quite a few. My search was for "USB power meter". I ordered one of these.
    USB Power Detector Voltage Current Meter Charger Doctor Mobile Battery Tester | eBay

    I have ordered stuff on ebay before that is shipped from China, sometimes it takes over a month to get it, so if in a big hurry, this is not the best source.

  9. #9
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    I've been charging a battery pack with my dyno for a few years now. But batteries keep getting better and better and charging with my dyno seems almost pointless now. My latest battery pack is a Mophie Power Station which holds 8 charges of my iPhone. That amounts to about eight days of riding. I tend to stay in a motel where I could plug in more often than that.

    If I were investing the money today, I'm not sure I'd put a dyno hub on the bicycle. Maybe somebody on an expedition type tour would do that. If eight smart phone charges are not enough, you're charging multiple tablets, etc. you could also bring two of these battery packs.

    Edit: I personally do like having lights that always work with no fumbling around with batteries. That's a valid reason alone, to use a dyno.

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