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Old 2005-01-31, 08:22 PM   #1
mikepenton
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Dynamo on a Uni for GPS/PPC power

Has anyone ever tried a dynamo on a Uni?

I've just got a PocketPC with built-in GPS. Battery life is around 2 or 3 hours which is pretty hopeless if I want a constant fix & a track. The set-up I'm thinking of is a Pedal & Power charger so I could make a cup of tea, run a mini fridge or even keep the GPS charged.

Apart from the bulk of the dynamo (2 inches or so projection from the sidewall), lack of speed, the frame-fixing issues and the water damage from landing in puddles/rivers, can anyone see any major drawbacks?

Thanks
Mike
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Old 2005-01-31, 09:01 PM   #2
markf
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get a better gps unit. there are some that have much longer battery life. and it might not work so well for uni but i've seen touring bikers with photovoltaics on the topp of their gear to charge stuff.
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Old 2005-01-31, 09:10 PM   #3
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I use the Garmin E-trex, it is a little backpacking GPS but it can show agerage speed, top speed, current speed and what not, its really little too.



you can get them for about 60 bucks
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Old 2005-01-31, 09:57 PM   #4
mikepenton
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A 'better' gps unit is not a sensible option. As I already have vector & rasterized mapping on the PPC there is no point wasting money on a second unit which duplicates the same tasks or offers much less. I know that I could have had a basic non-mapping GPS with a longer battery life and a seperate PPC for less money.
Hence the option of the dynamo.
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Old 2005-01-31, 10:18 PM   #5
Seager
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What type of batteries are you using? Try using NiMH with a high mah rating. Those last a ton longer than alkaline and are rechargeable.
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Old 2005-01-31, 10:36 PM   #6
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Re: Dynamo on a Uni for GPS/PPC power

Quote:
Originally posted by mikepenton
... can anyone see any major drawbacks?
Going through the electrical engineering pain of building such a unit. You can't just inject the power of the dynamo into the ppc. You need a regulating device with capacity in between. I don't know if such a thing exists on the market.

Edit: If I had clicked on your Link I'd have known better

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Last edited by wogri; 2005-01-31 at 10:39 PM.
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Old 2005-01-31, 10:36 PM   #7
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hmmm ... any of you guys seen the 'charging unit' part of that kit posted available for sale ...?

Cuz, I still have a generator that I've had since I was a kid that still works.
I believe it supplies the same volts/amp as the one in the kit.

Thx in advance.
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Old 2005-01-31, 10:37 PM   #8
john_childs
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I'd be concerned about how well it can charge the battery. It probably doesn't give a constant charge to the battery which could be bad for the rechargeable batteries. It might lower the useful life of the batteries. Could it end up over-charging the batteries?

Will the PPC be able to run off the external power? Will the Pedal Power thing give a consistent enough source of power so the PPC can run off the external power? Can the PPC switch from external power to battery power on the fly (for example when you stop pedaling)?

What happens if you run the Pedal Power backwards during an idle?

I'd also be concerned about the durability of the PPC. Those things aren't made to take rough or outdoor treatment.

The thing would probably be better suited for a 29er or a Coker on the roads (asphalt).
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Old 2005-01-31, 10:39 PM   #9
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Quote:
Originally posted by john_childs

What happens if you run the Pedal Power backwards during an idle?
It's AC current ... so doesn't matter.

I'm assuming it's got a capacitor to hold a converted DC charge.
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Old 2005-02-01, 03:48 AM   #10
Ken Cline
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Re: Dynamo on a Uni for GPS/PPC power

"Seager" <Seager@NoEmail.Message.Poster.at.Unicyclist.com> writes:

> What type of batteries are you using? Try using NiMH with a high mah
> rating. Those last a ton longer than alkaline and are rechargeable.


Not so. High capacity alkaline AA cells have more charge (2850 mAh)
than high capacity NiMH AA cells (2300 mAh). Not only that, but some
equipment (especially high current equipment like my Nikon Coolpix
800) can't cope with the lower voltage (1.2V vs. 1.5V) of nickel
chemistry batteries.

Rather than dragging the wheel with a generator, I'd look into hooking
up a rechargeable (gel-cell or external NiMH pack) battery to the
computer/GPS.

Ken
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Old 2005-02-01, 10:58 AM   #11
Seager
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Re: Re: Dynamo on a Uni for GPS/PPC power

Quote:
Originally posted by Ken Cline
"Seager" <Seager@NoEmail.Message.Poster.at.Unicyclist.com> writes:

> What type of batteries are you using? Try using NiMH with a high mah
> rating. Those last a ton longer than alkaline and are rechargeable.


Not so. High capacity alkaline AA cells have more charge (2850 mAh)
than high capacity NiMH AA cells (2300 mAh). Not only that, but some
equipment (especially high current equipment like my Nikon Coolpix
800) can't cope with the lower voltage (1.2V vs. 1.5V) of nickel
chemistry batteries.
Ken
My Nikon Coolpix 950 ran off low mah nimh much better than it did Alkalines (10 hour battery life vs 3 hour) and this was with the nimh technology they had 3 or 4 years ago. They're much better now.

Different experiences I guess.
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Old 2005-02-02, 03:23 AM   #12
Ken Cline
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Re: Dynamo on a Uni for GPS/PPC power

"Seager" <Seager@NoEmail.Message.Poster.at.Unicyclist.com> writes:

> My Nikon Coolpix 950 ran off low mah nimh much better than it did
> Alkalines (10 hour battery life vs 3 hour) and this was with the nimh
> technology they had 3 or 4 years ago.


I am skeptical of those numbers, but it is possible that your Nikon
draws more peak current than an alkaline battery can supply. If that
is the case, then Nikon had no business designing the camera to use AA
cells in the first place. More likely, you were using regular
alkaline cells instead of the "ultra" version, or you tried anemic
rechargeable alkalines.

But the facts remain: High energy alkalines offer 20% more charge
(mAh) than the best NiMH and higher voltage. Except for applications
where internal resistance becomes an issue (i.e. devices which drain
the battery in less than an hour or have high peak current
requirements) the alkalines win. Even so, I use NiMH rechargeables
for economy, conservation, and projects with heavy current loads.

Ken
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Old 2005-02-02, 08:03 AM   #13
Klaas Bil
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Re: Dynamo on a Uni for GPS/PPC power

On 01 Feb 2005 20:18:34 -0700, Ken Cline <ken.cline@cs.cmu.edu> wrote:

>But the facts remain: High energy alkalines offer 20% more charge
>(mAh) than the best NiMH.


I was skeptical (triggered by the word "facts") and did some Google
research. And found it's true. While NiMH AA size are already sold in
2500 mAh nominal capacity, the best Alkaline AA cells come out at 3100
mAh. 24% more (and then there's the higher voltage).

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Old 2005-02-03, 07:38 AM   #14
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Re: Dynamo on a Uni for GPS/PPC power

On Wed, 02 Feb 2005 07:58:16 GMT, Klaas Bil wrote:

>(and then there's the higher voltage).


I wrote that as an aside, as in "so the energy content is even
higher". But on reflection, the higher voltage of Alkaline cells might
mean that the current drawn by the equipment is that much higher too.
So unless your equipment actually needs the higher voltage, it might
be a disadvantage and the running times of NiMH and alkaline would
come out quite close.

But I'm not a battery expert. Thoughts anyone?

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Old 2005-02-03, 01:12 PM   #15
mikepenton
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Quote:
Originally posted by john_childs
Could it end up over-charging the batteries?

Will the PPC be able to run off the external power? Will the Pedal Power thing give a consistent enough source of power so the PPC can run off the external power? Can the PPC switch from external power to battery power on the fly (for example when you stop pedaling)?

What happens if you run the Pedal Power backwards during an idle?
It shouldn't over-charge the batteries, as an indicator light changes when it's fully charged. If it's plugged in & the car engine's off it still works on internal batteries OK.

If it gives enough power, and what happends it if runs backwards, those questions I'm not sure about. I've contacted the manufacturers about the output (without response). As Dynamos have no strict instructions on mounting, I assume that they could rotate in either direction.

True to form, a good question and one that I had not thought of! Thanks John!
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