The future of batteries?

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CasperFabricius
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The future of batteries?

Hi everyone,

I am growing increasingly annoyed with bad batteries in my laptop, in my phone, in my ipod and so on. While battery capacity is increasing, battery durability seem to be as bad as ever - after a few months, my batteries doesn't last anywhere near as long as advertised.

Lithium batteries seem to be the best technology for batteries currently, but what is the next big battery technology? All batteries available to consumers seem to loose capacity after a certain amount of cycles - how could this be prevented or minimized?

Cheers,
Casper Fabricius

jdh2550_1
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Re: The future of batteries?

Google on EEStor - and hope that these folks can actually deliver on their claims...

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

LinkOfHyrule
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Re: The future of batteries?

Me too. They would be a real boon. That (supposedly) 1MJ/Kg energy density is incredible. You really could match the range of gas cars with that.

Consider: Gasoline has a volumetric energy density of 38.4MJ/l. However, gas engines dissapate ~75% of that as heat. You can only really use 9.6MJ of that.
An electrical drive system (motor, controller, wiring, etc.) can easily reach 80% efficiency. So, you have 0.8MJ/l available to use.
This means that you need (volumetrically) 12 times as much capacitor when compared to gas. This might seem like a lot, but when you consider all the space taken up by CRAP in a gas engine that isn't needed by an electric motor it's not really a big deal. I'm pretty sure you could fit 12 gas tanks in a car minus the engine works.

Oh, also you could fill it up for, like, $10. What is that? Maybe 3 gallons of gas (soon to be 2)? ;)

About the capacity degradation on batteries: there really isn't much you can do about that.
Typically, this is caused by chemical and mechanical stresses on the electrodes. The charge/discharge cycle in batteries actually changes the chemistry and size of the electrodes. External thermal and physical abuse can make it even worse.
Capacitors, however, are different. Unlike batteries, they do not generate a charge. They store it between electrodes and insulators. Therefore, they do not change in chemical composition when charged or discharged, they simply gain an electrical potential. For all practical purposes, they have an unlimited cycle life. Their only disadvantage is that they have a linear discharge curve (oxymoron? :)). You need some sort of voltage balancing circuitry to keep the voltage stable.
I think the simplest (though possibly not most efficient) way of doing this is to have some setup that charges some smaller capacitors in parallel and measures the voltage across the individual capacitors. Then, when the stored potential reaches the desired voltage, flips on some relays or FETs to discharge them in series. Stick a smoothing capacitor in there to keep the ripple down.

...

Actually, that would be brilliant. Add a way to easily adjust the output voltage and...

Hmm...

Time to get out the protoboard...

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kevinwest
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Re: The future of batteries?

The oil and auto industry owns nearly all if not all the lead acid battery companies in the US!

It is the foreign companies that are making the breakthroughs in batteries. But US companies want you to buy batteries forever.

LED’s would use very little energy and last 1000 times incandescent light. The light bulb companies are not making LED replacement bulbs.

Rechargeable batteries are not pushed because they want to sell you the throw away batteries.

Good news, there are new batteries in research, some in the years past we said to last the life of the electric car, electronic device etc but never made it in production.

It will be a while for the ultimate battery to get here if ever. Too much money keeping things the way they are. Who will make a product that you sell once to someone and never again, no money in that!

LinkOfHyrule
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Re: The future of batteries?

Ultimate battery? What would that be like?

It seems to me the "uber-battery" would consist of thus:

1. Unlimited energy density. It just keeps on storing whatever you put into it.
2. No internal resistance. No voltage drop.
3. Infinite cycle life.
4. Flat voltage curve.
(Granted you'd need to calculate the state of charge by subtracting joules withdrawn from joules deposited, but I think it would be worth it.)
5.Extra large cupholders.

Hmm...I wonder. Exactly what would happen if you shorted it out? Since there is no resistance, it couldn't heat up, but then where would all that energy go? All I can figure is that it would generate some sort of super powerful EMP that irradited/atomized/otherwise annihilates everything within range...

Any thoughts?

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andrew
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Re: The future of batteries?

Hi everyone,

I am growing increasingly annoyed with bad batteries in my laptop, in my phone, in my ipod and so on. While battery capacity is increasing, battery durability seem to be as bad as ever - after a few months, my batteries doesn't last anywhere near as long as advertised.

Lithium batteries seem to be the best technology for batteries currently, but what is the next big battery technology? All batteries available to consumers seem to loose capacity after a certain amount of cycles - how could this be prevented or minimized?

There is no "best" technology. Lithium ion may have high energy density and specific energy, but they also have drawbacks such as cost, safety issues, discharge rate, cycle life, and shelf life.

I'm surprised your batteries are losing capacity so quickly. Spec sheets I've seen for lithium-ion say they will last at least 300 cycles to 80% capacity for the chinese cells. Maybe yours are getting very hot (because the electronic device is heating them up) and this is shortening the life? Maybe the high discharge rates are also adversely effecting the life?
Check this spec sheet for 2000 mAh 18650 cesls: http://www.batteryspace.com/productimages/li-ion/LC18650-2000.pdf

If it is battery cycle life you are worried about, consider buying electronic devices that will allow you to use AA or AAA batteries. Than you can either use NiMH or NiCad which will both last longer than lithium ion in terms of life. I've had the best experience with NiCad, but the energy density is much lower. I don't like the way most electronic devices now use special non-interchangeable lithium-ion batteries. I bought a digital camera that allows me to use AA batteries. NiMH and NiCad AA or AAA batteries are now pretty cheap and the capacity has been improved a lot. Good chargers for them are also pretty cheap, I got one from Energizer with circuitry to detect end of charge for $10.

I'll bet you could buy or construct a NiMH or NiCad C or D cell pack and put it in your laptop bag and run a cable to plug in the charger jack. If you can match the voltage it should work.

The next big technology to my understanding is LFP (lithium ferrous phosphate) which includes LiFePo4, and nanophosphate (A123s). They should offer much better cycle life than Cobalt Lithium-ion, higher discharge rates, faster charge rates, be safer, and have about half the specific energy. A123 is already selling cells to Dewalt to use in power tools.

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davew
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Re: The future of batteries?

Google on EEStor - and hope that these folks can actually deliver on their claims...

Years ago when Gizmodo started talking about eeStor they used a cheese sandwich to demonstrate the concept of a capacitor. (You want really wide pieces of bread and thin cheese.) Just recently they noted that they are still using the same picture of a cheese sandwich because there is still no product. They, and I, are starting to get a little pessimistic about eeStor's chances of coming up with a marketable product. I still hope, though.

"we must be the change we wish to see in the world"

jdh2550_1
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Re: The future of batteries?

Cheese sandwiches (daveW) AND extra large cup holders (linkofhyrule)! Now I understand - it's a conspiracy (kevinwest) by all the 7-11 owners! Who says I can't learn things from the Internet? :-)

Apparently EEStor have pushed back their delivery date. They were supposed to deliver a pack with enough capacity to power a NEV to ZENN motors by the end of this year. I believe they are now saying middle of '08. Of course there are still plenty of folks saying "never gonna happen".

The other exciting thing about EEStor is that they claimed a 54kW device produced in high volumes would cost around $2000. That would be amazingly cheap compared to batteries.

I too heard the cheese sandwich example - and the analogy that EEStor has made bread that is full of holes (nanotech sized holes) so that you can get more surface area for the cheese. But, alas, my understanding of capacitor technology is slightly less than my understanding of cheese... I'm hungry - please pass the grilled cheese and the super slurpy...

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

LinkOfHyrule
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Re: The future of batteries?

LOL cheese sandwich.

Anyway, I'm not the expert but it goes something like this:

A basic in electronics is that you can store electrons between a "sandwich" of insulators and conductors. Naturally, the more material you have, the more electrons you can store. However, the amount of electrons stored is directly related to the voltage applied. Eventually the capacitor and voltage source will balance out and the cap will stop charging.

Now the tricky stuff. The voltage required to store a certain number of electrons is also directly related to the amount of space (as in a variable capacitor for you radio junkies) or insulator (as in everyday capacitors in electronic circuitry, and supercaps) between the electrodes. The closer they are, the less electrical potential is required. However, this introduces a new problem: If you apply too great a voltage, the insulator between the electrodes will suffer dielectric breakdown, and the cap will be destroyed.

However, the voltage required to do this is different for different materials. You can use literally almost anything to produce a capacitor. In fact, if you stuck some aluminum foil on the two sides of that sandwich, you could transform it into a literal capacitor instead of just an analogy! Granted, foil wrapped sandwiches (be they cheese or, mmmm, turkey) don't make very good capacitors. You need dagerously high voltages to store any decent power, and they don't last very long, what with the molding and all. The relative abilty to resist high voltages is called a materials dielectric constant. The higher the dielectric constant, the higher voltages they can withstand. Two of the best (known) ones are aluminum oxide (big ones are commonly used to power microchips) and aerogel (the superlight carbon foamy stuff that you can make supercapacitors out of). I have a couple of the aerogel Pseudocaps (2.3V 50F, 2.5 V 20F, and a little 2.5V 1F one). Neat little things, but they don't come close to matching the energy density of batteries, though (when compared to batteries) they are pretty much unmatched in power density.

To put it simply:
To get the highest possible amount of energy stored, you want lots of very thin componentry in the cap, and the insulator should have the highest dielectric constant you can get. Nanofine materials make this possible.

Now, if you'll excuse my, I'm hungry. I'm going to go make myself a cheese and tantalum...er...plastic film...dammit...turkey sandwich.

JD, your on your own. My fax/teleporter is on the fritz. Sorry.

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andrew
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Re: The future of batteries?

LinkOfHyrule,

You got me thinking about giant cheese sandwiches, err umm capacitors. What about a giant insulator? Or taking a traditional insulator and putting a whole lot of it in so you could up the voltage a lot?

Energy stored in a capacitor is E = C * V ^ 2

E = potential in volts

C = capacitance in Farads

E = energy in joules

The mathematical relationship demonstrates that an increase in voltage could lead to a lot more energy stored.

Say you take a 100 Farad ultra capacitor. It might be designed for about 2.5v. That'll store 312.5 joules or .087 whrs. Not exactly enough to drive to work.

What if you disassembled the capacitor and put a lot of insulator between the electrodes. If you could insulate it well enough to up the voltage to 1,000 v than you could store 50 million joules or about 13,890 whrs. Enough energy to drive about 50 miles.

This would be like adding a load of cheese between the bread. Aside from all the calories and cholesterol you are looking at a better insulator.

Please tell me why this won't work, as I'm sure someone has thought of it.

Dammit now you got me hungry too. Cheeseburgers anyone?

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LinkOfHyrule
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Re: The future of batteries?

Well, that's sort of what they're trying to do:

You could technically do that, but it wouldn't really amount to better energy storage. Like I said, the further the electrodes are away from each other, the more electrical potential you need to store the same amount of power. What is important is the converse (no, not the shoes) of this: If you move the electrodes farther apart, you won't be able to store as many electrons per volt. So (assuming in the unlikely event that you can match the nanoscopic construction of the capacitor) you are going to need more capacitor.

Hmm, that's seems worded funny.

Maybe I can put this in simpler terms with an example:

Take your 100F supercapacitor. For all intents and purposes lets say you could actually take it apart and put it back together without destroying it. Also let's assume we don't alter any of the electrical properties of the materials while were doing it.

"Energy stored in a capacitor is E = C * V ^ 2". You got the right answer (312.5J) so I think you forgot the divided by two part: E = 1/2C * V ^ 2. I usually (I use that term loosely: I don't think I've actually written it out in my whole life) write it as 2E = C * V ^ 2. Just seems easier that way. Don't know why.

Now, assume we keep the cap the same size. You start with a maximum potential of 2.5V. You want to up that potential to 1,000V (seems kinda dangerous, but all the more fun ;)). So your going to need 400 times the insulator. Were talking nano-scale here so that's reasonable. So you stuff a bunch of insulating material between the electrodes.

But what happens now? You've increased the distance between the electrodes! So now the capacitance value goes down. But it is not 1/400 of the original capacitance value. You are now down to a measly 0.000625F (625uF)!

Let's plug that in to our equation: E = 1/2(0.000625) * 1000 ^ 2
E = 0.0003125 * 1000000
E = 312.5!
You get the same value!

Now, let's take for example my two capacitors: One is an ELNA Dynacap, rated for 2.5V at 20F. The other, a Gold Cap, rated for 2.3V at 50F. The ELNA is an aerogel Pseudocapacitor (I think that's a proprietary thing). The Gold Cap is made out of idontrememberwhatium. They are almost exactly the same size (maybe 0.5mL different).

ELNA: E = MC^2

wait...no...

ELNA: E = 1/2(20) * 2.5 ^ 2 = 62.5J

Gold Cap: E = 1/2(50) * 2.3 ^ 2 = 132.25J

More than double the energy density for the Gold Cap.

I probably screwed up something somewhere, since it gets way more complex than that, but basically:
In order to store more energy in an identically sized cap, you don't need more insulator, you need a better insulator.

If you really want to really get technical you going to need all of this. Good luck.

Now about that cheeseburger...

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CasperFabricius
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Re: The future of batteries?

Very interesting discussion. I'm sorry I haven't participated the last few days, but the email notifications got caught in my spam filter, and I only just discovered all your answers today.

jdh2550_1; I've heard about EEStor elsewhere, but the whole thing seem very secretive and could be just hype. So it is interesting to hear that they could be ready as soon as next year.

LinkOfHyrule; thanks for explaining the issues and possibilities on the subject. Except perhaps for your last post I think I'm able to follow, and I'm neither an engineer nor physicist. I especially find your point about better insulation interesting.

Andrew; I understand from your post that my lithium-ion batteries are supposed to have many more cycles in theory, but they just don't seem to in practice. I guess I'm not using them in an optimal way, but then again, li-ion is not supposed to have any memory, right? Thanks for pointing me to LFP, I'll look into that as well.

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