Shakeable Batterys - Hmmm.....

The problem with using strange shape batteries is that, by default, they're less versatile. Imagine trying to cram a shoe-sole shaped battery in to your TV remote.

Aside from that, I tend to agree. There is a lot of wasted energy out there. The problem is that, sooner or later, fossil fuels will run out and we'll be forced to rely on other methods of generating enough energy to supply the world's ever-growing demand.

One thing we have to wonder, though, is whether these shakeable batteries (as well as possibly being more practical) are actually energy efficient. In other words, it will take energy to make the battery (almost certainly more than a normal battery requires) so is the net energy for this addition positive or negative?

Let's say it takes the equivalent of...*pulls a number out of a hat*...20,000 shakes to generate the same amount of energy as it would have taken to add the charger element to the battery (regardless of material components). If you shake the battery less than 20,000 times over the course of its life then you'll have spent more energy than the extra energy "available" that you've created.

One major physics problem is the law of entropy. In summary for those who don't study physics, nothing is 100% efficient so some energy is wasted. This results in energy "spreading out", so unless energy is put in to a system (from the Sun, for example) we'll eventually just end up with energy turning in to useless forms. Luckily for us, we've got the Sun so we can use that to create energy, either directly or indirectly (growing crops, which feed animals, which we eat, which gives us energy).

The important thing to realise here is that, overall, you'd be using more energy either way to convert to the same amount of electrical energy than if you used regular batteries.

Let's say that every battery (rechargeable or not) has E J of energy in it at maximum capacity. That energy is used at the same level of efficiency (namely once charged they are, in effect, the same) but they are charged at different levels of efficiency. Once you've used it all, you've used a total of E J of energy.

You now have three options, depending on which battery you used and whether you want to (if possible) recharge it or not:

1) Non-rechargeable battery: buy a new one, another E J of energy is available to you, generated at efficiency x.
2) Rechargeable batteries: buy a new one, another E J of energy is available to you, generated at efficiency y.
3) Rechargeable batteries: charge, generating another E J of energy at efficiency z.

Using this model (ignoring the idea of energy used going to the shops to buy batteries), we can work out whether it's actually worth buying rechargeable batteries or not.

Regular Batteries

x = E / energy input

Rechargeable Batteries

y = E / energy input
z = E / manual energy input

Looking at that, as E is constant throughout, to make rechargeable batteries worthwhile one (or both) of the following conditions neeed to be met:

y > x
z > x

If y is greater than x, rechargeable batteries are able to be created using less energy than non-rechargeable ones (efficiency-wise), regardless of their ability to charge. If this is the case, there's no need to buy non-rechargeable batteries.

If z is greater than x, you can charge rechargeable batteres more efficiently manually than non-rechargeable ones can be charged. If this is the case (assuming y < x, which is likely), there's a point where it becomes worthwhile to use rechargeable batteries over regular ones. This point is determined by the exact values, but the key here is that the less efficient it is to make rechargeable batteries over non-rechargeable ones (charging ignored), the more shaking you'll have to do. It also clearly depends on how efficient the charging process is.

Bear in mind that this model is still ignoring wasteful "dead" non-rechargeable batteries. I don't care how efficient they are, eventually you'll run out of material to make them, and have to start breaking apart the old batteries and making new ones out of them (pouring a lot of energy in while doing so). This may be a long term thing, but it still need to be thought about.

Anyway, charging the batteries manually may not be as inefficient as you might think. Current power stations are very inefficient, as a lot of the energy used to create electricity is "wasted" as heat. Compared to them, even if it is on a small scale, charging manually (assuming you don't jump up and down to do it, and move the rest of your body as little as possible) is relatively efficient, as there's less stages in it (sort of, it's a bit more complicated than that ).

My point is that, overall, you'd probably use less energy in the charging process, but the scale of it means that the time it would take makes it currently non worthwhile. If you don't charge the battery, however, it's still more efficient to get non-rechargeable ones than rechargeable ones. Basically, whether you should bother or not is pretty much entirely dependant on whether you intend to recharge it or not. If you're going on a hiking trek and want to recharge your phone it could be a valid option, but for everyday use putting the time and effort in to shaking it is generally too much hassle. They're almost certainly possible to make but only really useful for the majority of us if we can charge them passively (like in many of the methods I listed in a previous post).

While we're on the topic, anyone heard about so called blood batteries? Could be pretty interesting in the future...

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I love your ideas, and your right, theres a very large amount of wasted energy that could be utilized to charge these batteries. perhaps we could have a much larger battery that was shaped like the sole of a shoe..
and put the battery between the sole and the rubber.

Sure, the battery would stink, but due to size it would store more energy/charge faster. Might hurt your feet a little too.

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Nice, 32J of energy...you'd have to really want to change the channel to shake it that much.

One thing I did think about, what if you had - for want of a better word - slots in your shoes or clothing in to which you could place batteries, so that when you walked or moved they charged up? Sure, the rate of transfer would be even slower, but over a longer period of time with little effort.

Thinking along the lines of "portable" charging, could you have clips on the wheels of your bicycle, on to which you could attack the batteries, which would charge them up a lot faster than normal. We know that you cna have dynamos on your bike to power a light on the front, so using the same principle you could quite happily charge up the batteries by shaking them.

I think the key here is to have batteries that can be manually recharged, rather than requiring specialist equipment or to buy a new battery. The shaking idea alone wouldn't provide enough energy, but there's probably a good deal of practical ways of using every "wasted" energy to do that for you. Attach it to your dog's collar and watch it charge as he runs about in a field, have a spring that clips to your washing line, letting it bounce (and charge up) in the wind, the ideas are there.

Assuming you need to charge it without any clips or whatever, it's still possible as you can just shake it manually. Don't expect to run anything for long, though.

Any other ideas?

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I think its a great idea, but I'm agreeing with Mordent in the that the energy created wouldn't really be worth the amount of shaking.

I weighed several AA batteries, of different brands, and found that they ranged from 22 - 25 grams of mass. That about halves the amount of energy mordent came up with, so lets say .045 J. Now he assumed the battery was its own charger, but then another problem comes up. How does it store its energy? Earlier things like on/off switches, storage units, ect. have been suggested. So lets say we have a small storage unit that takes up 1/8 of the battery for arguments sake, along with an "on/off" switch on the side of the battery which takes up 1/16 of it (unrealistic but work with me here). Thats 3/16 of a battery, leaving 13/16 of it.

13/16 = .8125
.045 * .8125 = .0365625 (Be generous, call it .04)

So now you'd only be generating .08J per "shake" of your arm, instead of .2
Thats 12.5 "Shakes" for 1 J.
Now considering most people would get tired after a minute of shakes, especially at the previously given 240 shakes per minute..the shakes would likely decrease VERY rapidly, I'm gonna say 400 Shakes by the third minute.

400 / 12.5

Congratulations, you've generated 32J in 3 minutes.
Reminds me of nuclear fusion. Except much more wasteful?

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Not a damned clue. Using the idea of energy, plus a bit of physics, you can see that the amount of energy you'd generate by shaking is minimal:

work done = force * distance

distance = 0.2 (I'm guessing here, but 20cm sounds about right)
force = g * 0.05 (mass of battery: if anyone's got one to hand and can get the mass, that'd be useful. For the sake of argument, I'm assuming 50 grams)

work done = 0.05 * 9.81 * 0.2 = 0.0981 J (call it 0.1 J)

On the basis that all of the battery is the "charger", you'd get 0.1 J per move of your arm, so 0.2 J per "shake". Again, assuming 100% efficiency, you'll be able to generate 1 J every 5 shakes. Going for 240 shakes per minute (if you can last that long ), you'd manage 48 J.

In short, assuming 100% efficiency you'd be able to generate enough power to give a device that ran at 0.8W the equivalent of 1 second of charging for each second of running. Most battery powered devices (I believe - I'm assuming AA standard here) use more than 0.8W (don't quote me on that, I'm merely making an approximate guess. If anyone's got any decent number on that I'm happy to hear them), so you'd have to shake it for longer than you use it. So yeah, I'm not so sure it'd generate enough energy, really. Sure, in an emergency you could sit there and shake it for a few hours, but meh. For things like television remotes, or other low power devices, I guess it wouldn't be so bad.

Thoughts?

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