Ultracapacitors Soon to Replace Many Batteries?

einhverfr writes "According to an article in the IEEE Spectrun, the synergy between batteries and capacitors — two of the sturdiest and oldest components of electrical engineering — has been growing, to the point where ultracapacitors may soon be almost as indispensable to portable electricity as batteries are now. Some researchers expect to soon create capacitors capable of storing 50% as much energy as a lithium ion battery of the same size. Such capacitors could revolutionize many areas possibly from mobile computing (no worries about battery memory), electricity-powered vehicles, and more."

Don't short it out...

[kcbanner]

...your fingers may become part of the capacitor.

Do they burst and leak fluid?

[Anonymous Coward]

Do they burst and leak ballast (the fluid between the plates of a capacitor) like the capacitors commonly used in cheap motherboards today? I've heard that this ballast can be a serious health and environmental hazard. Of course, we all know that it often destroys motherboards by causing them to short circuit.

NiMH are also affected, in a different way.

[porky_pig_jr]

NiMH can be screwed up by overcharging, with the end result exactly the same as the memory effect for NiCD: their capacity greatly reduced. This is my first-hand experience, not hearsay. You need fairly sophisticated charger for NiMH, the one that protects from overcharging. Mine didn't.

Re:Do they burst and leak fluid?

[Sanat]

In the early 60's i was working part time at a TV repair shop to augment my military paycheck. I was working on one of those old huge TV's in the wooden cabinet type of thing. i had traced the problem to a paper electrolytic of fair proportion.

I changed the capacitor and confidently looked at the waveform on the scope knowing now that there would be no more ripple on the line but to my amazement there was even more ripple. I looked closely at my installation job noting it was across the right terminals and the polarity was correct.

I pulled my head out of the TV cabinet to look at the schematic to envision what else might be wrong when the capacitor blew up like a small bomb leaving a boiling hot liquid paste where moments before my head was peering.

It turned out that the paper cylinder was installed backwards on the capacitor reversing the positive and negative terminals.

Even if the paper cylinder was backwards... one can still note the metal case of the capacitor being the negative terminal. I failed to do this.

This occasion added a new check I made each time for every capacitor installed after that.

 

What the engineers giveth...

[Colin Smith]

Microsoft taketh away.
 

Re:Do they burst and leak fluid?

[Two99Point80]

In about that same time period I was working on a homebuilt power supply for a ham transmitter. I had temporarily bridged in more filter capacity and shortly thereafter absentmindedly picked up the still-charged electrolytic by both leads - *one in each hand*. The PS was about 350 volts. Fortunately the muscle contractions flung the thing out of my hands. They say a learning experience is anything we survive...

Re:Lightning and capacitors?

[Wonko the Sane]

... yes, if you could build a capacitor that would survive a direct lightning strike...

Re:Don't short it out...

[ILuvRamen]

I dunno what exactly you mean by that but if it shorts out by natural circuit means as in a piece of metal touches both terminals on the capacity and it discharges half of the entire energy of a lithium ion battery all at once, UH OH! First it would probably arc enough to damage things around it. Second, if it doesn't them whatever metal takes the brunt of it would probably fly off in molten chunks. Don't say electrical shocks can't liquify and explode metal at the same time cuz I've got the burn marks in my arm and one of my tables to prove it. And third, I think that would release a bit of EM energy too so your HDD could be wiped.
It seems like the only advantages are that you can carry a full battery plus an extra amount of much less safely stored electricity and running the battery down to 0.0001% instead of 2%, which btw is extremely dangerous in the cold or for long periods of time because it will kill batteries so they can never be recharged again (that's happened to me too). This may be the dumbest idea ever.

Modern Ultracapacitors

[Anonymous Coward]

This news post excited me at first. Using ultracapacitors currently on the market you would something like 3Kg of big fat high quality ultra capacitors (3 or 4 at about $250US a piece) and a high-efficiency voltage boosting circuit to power your notebook computer for a time period comperable to a standard 2.5 to 3hr LiIon battery. Ultracapacitors, Supercapacitors, and other high-density high-capacity over physical space capacitors have a very delicate construction of internal plates (usually in the form of ribbons in a very tight roll with some sort of gel in between). Because of the special gels used and the tight and fine construction within them they usually have a tolerance somewhere between 2.5 and 3 volts or so. Your notebook computer probably runs off of 12V internally.

One thing to note is that capacitors can charge almost instantly. So if their claims are true going from a 3hr battery to a 1.5hr capacitor of the same size would have the benefit that you could charge up very quickly. For me I'd take the 1.5hr capacitor simply for this, as I'm usually in transit less than an hour when using my notebook on battery power. For people who need more extended periods there are always external batter packs (which I use when I go on international flights or other long trips).

Interesting - crashes?

[iced_tea]

A bank of ultracapacitors releases a burst of energy to help a crane heave its load aloft; they then capture energy released during the descent to recharge. Buses, trams, and garbage trucks powered by the devices all run for short stretches before stopping, and it's during braking that the ultracapacitors can partially recharge themselves from the energy that's normally wasted, giving the vehicles much of the juice they need to get to their next destinations.

So what happens if the vehicle has to make a series of emergency stops (or a series of emergency actions)? If a car powered by this technology wrecks or impacts with another car, would it not be feasible that a significant amount charge would be depleted during an impact because the energy could not be fully recovered?

I assume it would take a series of such impacts though to fully deplete a charge. *shrug* But it might be something worth taking into consideration.

Or make a handy exploit... just get the guy riding in the car behind you to bump you a few times and he's out of 'gas'. Or as another prank, find a way to fully discharge the capacitor of a stationary car in a few seconds, rendering it underivable without a booster charge.

Re:Myth

[AngryNick]

You use a cordless tool because:

a. You are climbing up and down ladders all day and don't want to trip over power cords
b. You work in a space with limited or no continuous power supply
c. You have 2 or 3 fully charged batteries and a quick charger
d. Not all tools work with compressed air
e. You kept slamming the cord to your old tool in the tailgate of your F350.
f. all of the above and a lot more.

Re:But entropy is reversible..

[Verte]

The problem is that the chemical processes involved do not coat electrodes evenly. If you are willing to try other methods of 'recharging', for example:

1. Pull battery apart.
2. Melt down the pieces.
3. Refurbish the electrodes and solute.
4. Rebuild the battery.

You can get the battery back to its original state. Otherwise, electrodes will always be built incorrectly [they become more and more 'fuzzy'] and performance will deteriorate.
The end result is that while it is possible to remove a sufficient amount of entropy from the system, it is not always easy, as in, easy enough to do on a regular basis. It is not a memory problem, it is an aging problem: as the act of recharging introduces entropy itself, and recharging happens within the battery, that is where the entropy goes.

Wrong technology

[einhverfr]

You are describing electrolytic rather than ultra (or super-) capacitors.

These are designed on a very different principle. Rather than using rolled up etched/oxidized aluminum foil (the oxide acts as the insulator), these use activated carbon electrodes and an ion-permiable membrane as the insulator. This creates a capacitor with a much larger surface area than a traditional electrostatic or electrolytic capacitor.

At any rate, that is the *current* generation (up to 2700 farad capacitance-- which is huge-- those capacitors they warn you about in the PC power supply are less than a farad). It looks like the use of nanotubes may allow for *far* more powerful capacitors.capable of delivering workloads sufficient to replace batteries in many applications.

Actually the current generations of ultracaps are already replacing batteries in electric vehicles and hybrid fuel cell vehicles, and a wide range of other applications. Especially in hybrid fuel cell vehicles, the reports at the moment indicate that they lead to better fuel economy than a traditional battery for storing eneregy from regenerative breaking, etc.

Re:Interesting - crashes?

[MillionthMonkey]

If a car powered by this technology wrecks or impacts with another car, would it not be feasible that a significant amount charge would be depleted during an impact because the energy could not be fully recovered?

If I'm reading your post correctly you're worrying about a loss of kinetic energy not being recoverable for recharging the capacitor. That's not more of a problem here than with any car. Air friction already produces similar energy losses without any crash. My Prius suffers from the problem you describe, but it's no big deal. It has ordinary mechanical brakes in case the regenerative braking cannot recharge the battery fast enough to slow down the car, but they rarely engage and the car has never needed a brake job because the battery (plus friction) is already pretty good at absorbing the energy.

With capacitors, the danger with a crash is an explosion. This could in theory release much more energy than the cars had in kinetic energy upon impact (like when an ordinary car's gas tank ruptures and ignites). While people like to worry about 911 workers with can openers unwittingly shorting out the NiMH batteries in a Prius, a short-circuited battery can only discharge energy as fast as the chemical reactions inside will allow. You don't necessarily get this protection with a cap. Basically the pulse width you can get from a capacitor is mediated only by its internal resistance and its magnetic induction.

That can still be considerable. I used to have a 100000 uF cap (they were just coming out in the early 90s, and this one was the size of a small stack of dimes). When I charged it to 5V and discharged it, I had to wait a few minutes for the thing to drain. It had electrical characteristics similar to those of a worn out rechargeable. But when one of those big HV paper-and-oil caps shorts out, wow. A friend of mine made a can crusher for the Rutgers physics department out of a car-battery-sized HV capacitor. It was the size of a car battery not because of its capacitance (it had an unimpressive 100 uF in that regard) but because of the high voltage rating (at least a few kV). Most caps can only handle 35 or 50 volts. The stored energy in a capacitor rises only linearly with capacitance, but quadratically with respect to voltage. This thing discharged through a coil of copper piping (6-7 turns) wrapped around a plexiglass tube with a soda can inside. When it discharged through the coil, it induced a circular countercurrent in the can. Then the magnetic repulsion between the coil current and the can current crushed the can into the shape of a pencil in an instant- BANG! It woke up all the engineering students, that's for sure. I think they still use it.

Re:Myth

[arth1]

While Li-Ion/Li-Polymer batteries don't have "memory", as per se, they do have load cycles with highly uneven wear. The more you discharge the battery, the more you wear your battery down per ampere used. Discharging from 33% full to zero (in reality when the protection circuitry cuts in) a single time cuts down your battery life more than discharging from full to 66% five times over.
    This is the main reason why it's recommended that you charge Li-Ion batteries as often as possible, and even "top them off" when used regularly[1]. If you use a quarter of a charge per day, your battery will last much longer if you charge it daily or every other day than if you charge it every three or four days, even though the "cycles" used are the same.
    I recommend keeping anything below 1/3 full for "emergency use" -- there when you really need it, but avoided otherwise.

If you frequently use a laptop (or cell phone) until it runs out of power, or even gets very low, it's better to go with a NiCd or other battery, cause Li-Ions will have a seriously short life span if used that way.

[1]: If a Li-Ion/Li-Polymer battery is stored, half charged is better -- the self-discharge and chemical damage done from this is lowest at around 40% charge, which due to the protection circuitry equates to about 50% on the meter.

Re:Interesting - crashes?

[fyngyrz]

With capacitors, the danger with a crash is an explosion.

No, it really isn't. There's this marvelous technology, instantiated in these crazy devices we call "fuses", see...

Seriously, all you have to do is fuse the array internally on a per-block basis, and any shorted module will blow the fuse(s) to its neighbors, and that's the end of it. No explosion. No nothing. Just pffft and some new fuses (which might take a service call, but heck, you just ran into someone else, that's the least of your problems.)

One of the many benefits of capacitor systems is that you can arrange them many ways for many varied benefits. Paralleled caps simply add, so there's no reason not to break a high energy system up into blocks, and many reasons to do so. Not the least of which is the above issue, but it also makes replacement and service less expensive, less complicated, and allows use of smaller, easier to manufacture parts. And of course it allows various kinds of charging models.

I'm inclined to trust the engineers. If I can think of it (and I am an engineer, but not that kind) then they've probably though of it a hundred times over. The main issue here is energy per unit volume, and to a lesser extent, per unit weight. When and if those issues are really solved, we're golden.

Re:Can you? There are other limits.

[MadUndergrad]

That's why you have a household capacitor bank that sips juice from the grid, then discharges quickly for just these sort of applications.

Re:Myth

[Duncan Blackthorne]

I assume you're using quick-charge batteries, charge in one to three hours? Here's why your battery packs are wearing out so fast:

1. They have limited charge/discharge cycles to begin with
2. Quick-charging batteries (e.g., at a rate faster than C/10) dramatically shortens the lifespan of the cells, regardless of whether they claim they're designed for quick-charging
3. Rapidly discharging the cells (as in high discharge-rate applications like a screwgun) also causes heating, which shortens the lifespan
4. Commencing a recharge cycle before the depleted cells have had a chance to cool after a high-rate discharge cycle is also very hard on them, further shortening their lifespan

Unfortunately that's just the way it goes with the application you're using them in; you have to keep working during the day, and that means keeping your screwgun supplied with current, which means quick turn-around on your battery packs. Ultracaps don't have a fraction of the capacity per cubic centimeter versus basically any rechargable battery technology, even if the huge ones that (for instance) Maxwell [maxwell.com] makes for things like subway cars and streetcars do have an incredibly low equivalent series resistance (and therefore capable of tremendous charge/discharge rates). Compare that to the energy storage density of Li+ [wikipedia.org]; we're talking roughly 29 times the density with currently-available COTS technology. I have every confidence that if enough research money is invested in developing the technology they can reach the aforementioned 50%, but they've got a long way to go to get there.

Re:What the engineers giveth...

[dintech]

Why is this off-topic? It's quite relevant. Why spend all this time developing energy efficient hardware without developing energy efficient code? Of course Microsoft aren't the only culprits of this. McAfee, I'm looking at you...

Re:Interesting - crashes?

[saigon_from_europe]

My Prius [...] has ordinary mechanical brakes in case the regenerative braking cannot recharge the battery fast enough to slow down the car, but they rarely engage and the car has never needed a brake job because the battery (plus friction) is already pretty good at absorbing the energy.

Actually, recuperative braking cannot stop the car efficiently. So you can use impractical but energy efficient recuperative braking + mechanical braking, or to use pure engine breaking.

These two processes are essentially the same thing - invert the current inside the electric machine and it will brake the vehicle. The only problem is how to do this. If you want to do that in a manner that every single joule finds it way to the battery, breaking torque will decrease as the speed decreases and you will have to apply mechanical brakes in one moment.

If you do this by forcing the same braking torque all the time strictly by the engine, which is quite simple to do, in one moment energy flow will not be toward the battery, but from the battery. This is due to internal resistance of the electric motor.

In general, electric vehicle must have mechanical brakes simply as a safety measure. But electric vehicles are essentially more safe that IC-based ones, as they always have two truly independent braking systems.

Re:Do they burst and leak fluid?

[smellsofbikes]

In the late '90's I was working at a contract manufacturing place, diagnosing failed motherboards. We had these enormous quad-CPU PA-RISC boards that had 5000 components on them.
Someone somewhere in the supply chain had gotten a reel of caps that had been loaded in the reel backwards -- I have no idea how. Anyway, the pick-n-place machines stuck them down, just like normal, some 500 per board or so, all with reverse polarity. We were building that type of board at about 30 per hour, and it took almost an hour for the first boards to get to functional (power-up) test.
At that point, the RP caps all vaporized at the same moment.
It was like a miniature war zone: the caps would blow out tiny flaming chunks of stuff, leaving little spirals of smoke, while tiny flames shot upwards and downwards out of the test racks. It was awesome, although I'm sure glad I wasn't standing right over the first boards when they went. They burnt holes deep into the 22 layer circuit boards.
Then we had the job of finding, removing, and replacing, by hand, 500 caps on each board, and if we missed even one: fwoom! there goes another board.
I don't think we managed to get a single board from that lot repaired and out the door.

Much smaller than your experience, but very impressive nonetheless.

Re:mod parent up

[Lord Ender]

If what you say is true, then who do the makers of NiCd batteries say instruct you to fully deplete batteries on the instructions that ship with the products? They don't know the properties of their own products?