> > Why does your client need a battery only? > =A0its their specification No. That's their request :-). Their specification is what they want to do - not HOW they want to do something - especially important as the "how" which they talk about may be irrelevant. To decide that a capacitor and a battery are not the same for the task you need to know what attributes they are looking for and then decide what can provide them. Some types of modern ultra high capacitance "capacitors" tend to be "battery like" in their action - the boundary is blurred. The most likely attributes of a battery which are considered important are energy retention with time or energy density. The latter is almost certainly unimportant here and some capacitors will do a very very good job of energy retention over time periods which are probably of interest. If you want a really good answer you need to ask really good questions. If you want an interesting wander through related and unrelated issues then doing it the way its been done so far is an excellent way to achieve that. Are you able to tell us as much as you know technically that isn't subject to non disclosure? Also, fwiw, the amount of energy that you say you can acquire is extremely small compared to the energy available in a single stride. A far more efficient harvester may help things greatly. eg a 70 kg person who loses the ebrgy taken to fall 10 mm in one footfall loses mgh =3D 70 x 9.8 x .01 =3D 7 W.s =3D 7000 mJ. If you are getting 0.3 mJ/ste= p as you report you are getting 0.3/7000 =3D~ 0.5% of the total energy. Even if you allow energy losses equivalent to 1mm fall you are acquiring only 5% of it. As padded soles or air soles may well flex by more than 1mm that energy should be readily available. eg using an air driven alternator using air from an air sole in tyhe show is liable to produce vastly more energy than you are getting. Using a rare earth magnet moving against a spring in a coil that forms part of a shoes padding action would produce substantial enhergy. Even pendulum harvesters should be able to produce more than that. 0.3 mJ =3D 3E-4 N.m =3D 0.3 n.mm ie a 0.3 Newton force from a 30 gram mass, moving 1 mm should produce the energy you are getting. A vertical resonating mass on a spring (Shaker torch with mods) should achieve more. Note that at very low voltages the losses in rectification can form a very large & of available voltage and synchronous rectification is desirable. There are energy harvesting Is available that will turn mV into V for charging caps or batteries. I mentioned one on list within the last few months. ...digs ... LTC3588 made specifically for pizo harvester. http://www.linear.com/pc/downloadDocument.do?name=3D35881f.pdf LTC3108 - TEG etc http://www.linear.com/pc/downloadDocument.do?name=3D3108f.pdf .... Russell > > > > > How does your client define battery? What chemistry? What voltage? > > > > > When you say you are able to generate 3mJ per 10 steps - How? Piezo, st= atic > > charges? How much current/voltage per pulse/step? > > > Piezo > > > > > First you said 40mJ, then 100mJ and now 60mJ. Which one is it? > > > you can store 40 and 60mJ in a 100mJ battery... > > > > > Is there any reason why the battery can't store more than xxmJ? > > > i need 3V output > > > > > There are still too many unknown parameters here to get you an answer t= hat > > may > > be of use to you. > > > > /Ruben > > > > > > > I am harvesting energy while walking. i am able to generate 3mJ (m st= ands > > > for milli) per 10 steps. > > > so in 200 steps i can generate 60mJ. i need to store this energy. If = i am > > > using an ordinary battery of 50mAh and 1.2V battery, 60mJ wont give m= e > > > enough voltage for power an LED. So i need a battery to store the ene= rgy > > and > > > power an LED for 1-2 seconds. I know i can use a capacitor, but > > > my client need a battery only. > > > > > > *Sarin Sukumar A* > > > > > > *Design Engineer* > > > > > > *ni Logic Pvt Ltd, Pune* > > > > > > *** +91 9372195481* > > > My profiles: [image: > > > Google]< > > http://www.google.co.in/search?q=3Dsarin+sukumar&ie=3Dutf-8&oe=3Dutf-8&= aq=3Dt& > > > rls=3Dorg.mozilla:en-US:official&client=3Dfirefox-a> > > > [image: > > > Blogger]< > > http://electronicsadvices.blogspot.com/2009/04/full-featured-pickit2- > > > clone.html> > > > Contact me: [image: Google Talk/] sarinsukumar [image: Skype/] > > sarinsukumar > > > > > > > > > > > > > > > On Wed, Oct 20, 2010 at 8:07 AM, Olin Lathrop > > > wrote: > > > > > > > Ruben J=F6nsson wrote: > > > > > A 2000uF capacitor charged to 10V. > > > > > > > > Yes, but you have to drain it to zero to get the whole 100mJ out. = =A0In > > > > practise you'll need a bigger cap or higher voltage. > > > > > > > > > > > > *******************************************************************= * > > > > Embed Inc, Littleton Massachusetts, http://www.embedinc.com/product= s > > > > (978) 742-9014. =A0Gold level PIC consultants since 2000. > > > > -- > > > > http://www.piclist.com PIC/SX FAQ & list archive > > > > View/change your membership options at > > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > > > -- > > > http://www.piclist.com PIC/SX FAQ & list archive > > > View/change your membership options at > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D > > Ruben J=F6nsson > > AB Liros Electronic > > Box 9124, 200 39 Malm=F6, Sweden > > TEL INT +46 40142078 > > FAX INT +46 40947388 > > ruben@pp.sbbs.se > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D > > > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .