[Cheesey]

Just found this:

http://www.reghardware.co.uk/2008/06/24/or..._phone_charger/

Quote

The Orange Dance Charge is a portable phone charger powered through the
kinetic movement of a system of weighs and magnets, which move as you groove.
The system’s contained within a jogger-style MP3 arm strap, which also contains a
storage battery for holding all the dance-generated energy.

So far, Orange has only developed a limited number of functioning prototype Dance
Charge models, which it’ll be dolling out to a test-bed of dancers at this year’s
Annual Mud Gathering, also known as Glastonbury.

Sounds pretty cool! Does anyone know where they'll be dishing out the prototypes?

[longshanks]

If my physics are correct (and its been a long time since I went to skool); A typical phone battery of 3.5v and 1000ma provides about 3.5wats of power. So to recharge it at 1.5 times the capacity of the battery (due to losses in the recharging process) would require 5.25 watts.

5.25 watts is aprox 4,500 calories you would need to put into the battery alone, that does not include the calories needed to run your body and other activity!

Hate to say this, but it aint going to work too well.

[Cheesey]

longshanks, on Jun 24 2008, 03:20 PM, said:

If my physics are correct (and its been a long time since I went to skool); A typical phone battery of 3.5v and 1000ma provides about 3.5wats of power. So to recharge it at 1.5 times the capacity of the battery (due to losses in the recharging process) would require 5.25 watts.

5.25 watts is aprox 4,500 calories you would need to put into the battery alone, that does not include the calories needed to run your body and other activity!

Hate to say this, but it aint going to work too well.

I think you've got a point about this not working too well. My physics is a bit rusty as well, but I don't think your calculation is right - you can't equate calories (energy) and watts (energy per unit time).

1 watt = 1 joule per second = 0.24 calories per second
1 battery holds 1000mAh at 3.5V = 1Ah at 3.5V

P = IV
=> 1Ah x 3.5V = 3.5 Watt hours
=> battery holds 3.5 x 60 x 60 joules = 12600 joules = 3024 calories

So I reckon you'd need to provide around 3000 calories of energy to fully charge a phone battery. That's about a day and a half's worth of food. However, a large proportion of the calories you consume are spent keeping you body temperature stable, or moving something other than your arm, so my guess is that it would take much longer to fully charge a battery this way.

You might be able to generate enough power to send a text or two, or make a short call, but I think it'd be much more effective to just buy a couple of spare batteries off ebay and charge them before you go

[snipe]

Guys your maths is off by a factor of a thousand. Calories that we talk about in food are actually kilocalories. Theres plenty enough energy to charge a phone from kinetic energy. Its not effecient (and a wind up system makes far more sense) but its perfectly possible.

[Cheesey]

snipe, on Jun 24 2008, 03:54 PM, said:

Guys your maths is off by a factor of a thousand. Calories that we talk about in food are actually kilocalories. Theres plenty enough energy to charge a phone from kinetic energy. Its not effecient (and a wind up system makes far more sense) but its perfectly possible.

Good point. I fail.

So a phone battery has a capacity of about 3 dietary calories (kilcalories). That's an impressively small amount actually.

This post has been edited by Cheesey: 24 June 2008 - 02:59 PM

[canish]

Cheesey, on Jun 24 2008, 03:56 PM, said:

Good point. I fail.

So a phone battery has a capacity of about 3 dietary calories (kilcalories). That's an impressively small amount actually.

hello i hope you get this and reply because i haven't got a clue about physics or electricity!!

this is something i have been trying to research for a while does anyone know the holding capacity of one of these devices? and how long it would take to charge it i don't know how much 3 dietrary calories is!!
also just going to throw it out there does anyone know roughly how much electricity glastonbury uses off the grid?
i have been thinking of a project for a while and your help would be much appriciated!
the idea is to use the people at glastonbury to create at least some of the energy being used there is no way of covering the whole electrical drain of the festival unless these new Nanogenerators are really as good as the americans say they are.
thank you for your time upon reading this!!

Regards

Adam