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Charging a Li Polymer battery with Super Capaciters

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cobra1

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Hi

I have been asked by a friend to build a device to keep his phone charged while out walking.
I have built a very nice coil to generate power but im having trouble with a part of the electronics.

My idea is to take the tiny amounts of power generated in the coils and store them in a Super Capacitor(s)

I have found some 20F/2.5v Supercaps at a decent price.

Heres the problem, i know how to make the capaciter charge and then power an led etc, but i dont know how i would go about feeding that power to the phone.

The phone requires a 5v source, and needs to be fairly constant, so i was going to use the supercap to charge up an internal battery (3.7v) this would then be stepped up to 5v for charging the phone.

does anyone have any ideas on how to use a 2.5v capaciter to charge up a 3.7v battery.
the capaciter can only be charged by the coils and its power needs to be transfered to the battery. Once it is in the battery i think i know what to do after this.

Hope my rambling makes sense
 
Kinetic piston chargers like the nPower PEG produce almost no real power, they simply keep their internal LiPo battery charged for emergency use only.

Your first step should be determining how much power your coil generates while walking.
 
I am aware that only small amounts of power are generated, on one site i looked at for some infor it said that after 2 mins of shaking (shake torch) the capacitor had 1v, not much power for sure, but imagine the cumulative power generated, just from walking..

Lets say for arguments sake i have a capaciter that has 1v of charge, how would i go about putting that charge into a 3.7v battery?? all the Li polymer battery chargers i can find require a higher input voltage than the battery itself, i.e 5v,
So does this mean i could do something as simple as use a dc-dc converter on the capaciter to provide me with a 5v supply to the battery??
This may not be very efficient so im thinking there might be a better/simpler way
 
For emergency phone use the Energizer Energi to Go (uses a pair of AA alkaline batteries ~5Wh for two batteries in series) can supply scads more power than a small kinetic charger. Your supercap is no match for a chemical battery on a weight basis.
eg: 2.4Wh per kg
WIMA SuperCap C Double-Layer Capacitors

Folks using the nPower PEG (did you at least look at the PEG?) would take 30hrs of continuos walking to charge its internal 1,000Ah battery (no indication on voltage so no idea of the Wh capacity on the PEG). A typical smartphone battery is around 4Wh and you'd need to supply more than that to charge it. If you want a really powerful battery pack the 60Wh Hypermac battery can power a cell phone for ages.
 
I have looked at the "PEG" and also at the system that M2E have, IT was this system that i liked best. They take small amounts of power store acumilate it in a super cap and then use it to charge an internal battery. This battery can then be used for a number of things. I like this idea better also due to the fact that once the capacitor is charged (only holding a fairly small charge) any further motion is wasted as it cannot be stored. By storing it in a larger battery it will be more benificial long term.

I know there are probably a million other "better" ideas to make a phone last longer, but with such a device just having it in the glovebox for a month will charge it up for when it is required, solar panels, and wind in this case are not much good.

The battery to be charged in my case would be a 3.7v/1300mAh
 
was using the glovebox as a example of how the general movement of things can accumilate power over time, probably a really bad example actually now i think about it lol
 
I expect you've thought of this but why not put 2 caps in series making one 10F at 5v,.... then you wouldn't need the battery would you? .. might have to increase windings on coils though....
 
There are some low power boost switchers that work down to about 0.8 vdc input. Look at the sites for Maxim, Linear Technology, and Texas Instruments.

Most small AAA or AA single battery MP3 players have these switchers to boost the battery up to a voltage similar to that required to charge a LiPo battery. Because they work down to such a low voltage they can 'milk' an AAA or AA battery dry, extracting every bit of capacity from battery.

For a cellphone charger, you are better off with a hand cranked dynamo generator.
 
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I bought a cheap Eton Clipray crank powered flashlight with USB charger. Pretty neat and should be fairly easy to hack (the USB is not on the battery and has to be constantly cranked to charge your cell phone)
**broken link removed**
 
How about a small solar panel when out walking as a primary source? Have it secured by some sort of harness that you wear on your back, a bit like a solar backpack.. :)

Caravanners use them to keep the 'van battery charged when there is no mains power available
 
I bought a cheap Eton Clipray crank powered flashlight with USB charger. Pretty neat and should be fairly easy to hack (the USB is not on the battery and has to be constantly cranked to charge your cell phone)
Always thought u were a bit of a crank
 
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