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

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.

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

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.

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.

Re: Dynamo on a Uni for GPS/PPC power

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 :slight_smile:

Wogri

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.

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).

It’s AC current … so doesn’t matter.

I’m assuming it’s got a capacitor to hold a converted DC charge.

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

Re: Re: Dynamo on a Uni for GPS/PPC power

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.

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

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).

Klaas Bil - Newsgroup Addict

It’s impossible to get old when you ride a unicycle - John (what’s in a name) Childs

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?

Klaas Bil - Newsgroup Addict

It’s impossible to get old when you ride a unicycle - John (what’s in a name) Childs

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!

Re: Dynamo on a Uni for GPS/PPC power

Klaas asked if the higher voltage of alkaline cells results in more
current drain (thus shorter life). The answer is a qualified yes -
current draw will be higher at higher voltage into a resistive load -
but there are some significant qualifications.

First, if the resistance of the load is not significantly greater than
that of the battery, the battery’s voltage will drop. Unfortunately,
that means energy within the battery is being wasted, heating the
battery. Additionally as you increase the current being drawn from an
alkaline battery, you reduce the total charge it can provide. NiMH
cells have a flatter voltage vs. discharge curve and are consequently
far less susceptable to this.

But there’s more! High tech toys (er… I mean devices) these days
are beginning to use very sophisticated battery management technology
in order to maximize battery lifetime. The options include
step-up/step-down switch mode regulators, which suck only the required
power from the battery, drawing less current at higher voltages and
continuing to operate as the battery voltage drops below thresholds
that would ordinary mark the end of the battery’s useful life.

By the way, I was wrong when I suggested you could efficiently draw
current from an alkaline cell in an hour. That was a bad assumption
on my part, and devices that use current at that rate will definitely
benefit from Ni-, Li-, or Pb-chemistry batteries. You can find
discharge curves in the OEM section of battery manufacturer’s web
sites. To get near the rated charge out of an alkaline, you’ll neet
to use it in a device that runs for 8 hours. I even found a
recommendation on Nikon’s web site to not use alkaline batteries in
their Coolpix cameras! Go figure.

Ken