Japanese printer company Brother has invented a battery that can be recharged by shaking it. It’s intended for devices like remote controls that use very little power and would normally require infrequent battery charges, so unfortunately you couldn’t use it to power a car that could drive forever on a bumpy road.
… at least, it works a little bit. You can often squeeze a bit more use out of a “dead” alkaline battery by vigorously shaking it, it seems to work by mixing the chemicals inside. But it usually only works once, and only for a short time. Also, while I’ve had success squeezing a bit more life out of alkaline AA batteries this way, it doesn’t seem to work at all for NiMH batteries.
Is anybody else thinking of an over-unity bedroom-drawer application for this thing?
Well, now we can make a vibrator that gets energy from vibrations.
Well, now we can make a vibrator that gets energy from vibrations.
I was just thinking of that
Gee, I’d never have to change batteries, it’s so annoying when they die in the middle of something…. 
Gee, you did it! You just invented perpetuum mobile!
Energy is always lost when something is using it, usually converted to heat. A perfect system would be a perpetual motion machine, but that is impossible.
However, you can create systems that recycle as much of the energy as possible. For example, when we are walking, all of the energy we expend is lost. A system in our shoes that converts pressure to electricity (piezoelectricity it is called) can recharge our iPods or mobile phones.
Also the same technique can be used in roads specially constructed to create electricity when a moving car passes over them. Such a project is already being used experimentally.
+1 to vasper.
Period.
Q.E.D.
Edited 2010-07-21 09:56 UTC
Not really. A huge part of the energy is recycled through elasticity in our tendons and joints. That’s why a human can walk using only 50 W of power, while most human-sized walking robots need something in the order of 700 W.
The human body is efficient in it’s workings. That isn’t the same as recycling energy. Anyhow, the energy expelled from the body in the form of kinetic energy can be harvested by piezoelctric mechanisms to create electricity.
Emphasis for typo.
That is not true. The human body is really inefficient for walking. I do not have the data with me right now, but it is definitely quite a bit less than 50% efficient. That, of course, is compared to wheels, which are much more efficient.
What happens is that the robots are much more inefficient than humans, not that humans are efficient at walking. That is quite a big difference, and is also the reason why we can harness energy out of walking by having these machines in there.
Furthermore, I can tell you that efficiency is not what is evolutionarily selected for, so there is not much point in this discussion. I think a compromise between maximising power output (so that you can push harder than you need), efficiency, generality (not stuck to just flat land like wheels are) and minimising materials (to save on muscles and whatnot) is what is wanted, so the inefficient design is actually wanted to be so.
Given less constraints than nature, we ought to do a lot better, but alas the maths is not there yet.
Once there were wristwatches that worked on that principle, weren’t they ? Maybe still are… I don’t know.
Those are mechanical, mostly. (and they are called automatic watches, with the electric ones also known as automatic quartz).
Apparently, reclaiming minute amounts of energy in electrical form from shaking is terribly inefficient compared to what was achievable with mechanical systems. Hence the market proliferation of mechanical systems. Not to mention that automatic quartz have mechanical faces too.
I suppose we still have to thank brother (reminds me of big brother) for appropriating the idea into TV remote battery form. Quite ingenious.
Yeah my watch is an Invicta Ocean Ghost which is self winding and it has a glass backing which shows its mechanics.
There is a metal wedge that rotates around a pin in the center and winds the watch. If you don’t wear it every day it winds down and stops. I’m thinking it must be geared very well because winding older watches required quite a lot of torque.
I would suggest gear ratios to help solve that problem.
ie when manual winding, you can supply more torque, acceptable as long as you finish winding before you the day ends. When winding by shaking, you just have to average more winding than consumed in order for it to automatically recharge, which is a much lower constraint. That means, the winding can take hours on end to complete, in many more rounds than a human will have the patience for. That is why we can expect infinitesimal torque requirements in automatic watches.