Author Topic: capacitor storage (Read 738 times)

solarbbq · « **on:** February 10, 2005, 11:06:34 AM »

Hi all,

did search found nothing on this topic

capacitors for storing electricity

Noticed some toy planes with small electric motors have capacitors for storage ( i think). Got given a torch today which stores electricity by small capacitor.

You shake the torch a fairly hefty neo-mag goes through simple coil producing electricity according to faradays law,

small capacitor stores the energy, one bright led acts as torch. 30 sec of shaking torch makes led on for about 5 mins.

My question is this:

anyone got any knowledge on storing energy in capacitors and how it is released slowly. Any ideas on potential for storing decent amounts of energy?

Are special capacitors used. I will do a google and search and see whats around about this.

JeroenH · « **Reply #1 on:** February 10, 2005, 04:28:33 AM »

Noticed some toy planes with small electric motors have capacitors for storage ( i think).

Those caps or for noise suppression. Electrical noise of course, not acoustical noise :-) They are fairly small caps and do not store much energy.

anyone got any knowledge on storing energy in capacitors and how it is released slowly. Any ideas on potential for storing decent amounts of energy?

I noticed this thread: http://www.fieldlines.com/story/2005/1/6/145010/1135

Scroll down some to a post by 'richhagen', he has posted a picture of a board with lots of caps on it. Doesn't store much energy though.

drdongle · « **Reply #2 on:** February 10, 2005, 05:40:37 AM »

Super/ultra caps are making there appearance in numerous devices, mostly for power backup, and peek demand applications, and the usual memory retention applications. check out http://maxwell.com/go.php?id=102 for more info.

finnsawyer · « **Reply #3 on:** February 10, 2005, 07:59:14 AM »

A one farad (humongous) capacitor at ten volts will store 50 joules of energy. Discharge this in one second and you only get 50 watts average. I can design a circuit that will discharge a capacitor at a linear rate, but maybe not at the current level you'd like. Not really practical for energy storage.

TomW · « **Reply #4 on:** February 10, 2005, 09:16:48 AM »

solarbbq;

This has been an ongoing topic of discussion on IRC along with devices that could use them. With the advent of Car audio stiffening caps the size of huge value caps has gone way down. They come in values of hundreds of farads in smallish packages and are pretty expensive yet.

I believe that sooner or later we will see caps replace some batteries.

Caps have the big advantage of being able to cycle from fully discharged to zero to fully charged to rated voltage indefinitely with no "memory" and no damage.

Just a matter of time.

Cheers.

TomW

richhagen · « **Reply #5 on:** February 10, 2005, 09:49:20 AM »

The super or ultra capacitors (EDLC) made by Maxwell, Tavmirina, Ness and others are able to discharge and charge much more rapidly than batteries. They are finding uses in vehicle power trains for this reason, they are better for accelerating a car quickly and at recapturing the huge inrush of current from regenerative breaking. They are essentially always used in conjuntion with batteries as while the power to weight ratio (ability to discharge a given amount of current all be it for a short time) is better than batteries, the overall energy density is currently much less than batteries. ECASS of Japan has plans to build a primary power system for vehicles using capacitors, however it is quite a ways off in the future by my best guess. Capacitors have improved their energy density by orders of magnitude over the years, and if they can push that envelope another order of magnitude, then they will have distinct advantages to batteries in life expectancy and efficiency of charging and discharging. Leaving a typical carbon based ultra-capacitor at a 0% state of charge will not damage it. Unlike batteries, which rely on a chemical reaction that takes a specific amount of voltage to initiate, and hence are relatively flat in voltage as they charge and discharge, capacitors increase in voltage as they charge. The equation for the amount of energy stored in a capacitor is 1/2C*V^2 where C is the capacitance in Farads, and V is the voltage across the capacitor. Because the stored energy is related to the square of the voltage, if you discharge a capacitor down to 75% of its fully charged voltage, you are discharging 1/2 of its stored energy. This means that you either have to have circuits that can tolerate a more significant voltage change than would occur with a chemical battery, or you would have to significantly oversize your circuits. I believe it is likely possible that the energy storage density of ultra capacitors can increase to be near that of lead acid batteries in the future with the use of better electrolytes and improvements to the microstructure of the electrodes. With lifetimes of over a hundred thousand charge and discharge cycles, I think they will become viable primary power sources for applications such as remote power, utitlity substation back up power, and eventually vehicle power trains. All of this is still off in the future however, and for now, storage batteries are a better option for remote power, as it would take a fortune in money and a tractor trailer full of capacitors to power your home at present. For now they will see ever increasing use in burst power type applications at which they excell relative to battery technologies. Rich Hagen

richhagen · « **Reply #6 on:** February 10, 2005, 09:51:39 AM »

in the paragraph above, the line "oversize your circuits" should have read "oversize your capacitor bank" Rich Hagen

richhagen · « **Reply #7 on:** February 10, 2005, 09:59:00 AM »

it stores about 1755 Joules of energy at full charge of 15.3 volts. This is equivelant to 1/2 watt for an hour if you were to fully discharge it, or about a quarter of a watt for an hour if you discharged it to about 11 1/2 volts for running 12 volt equipment. Rich Hagen

RatOmeter · « **Reply #8 on:** February 10, 2005, 10:11:42 AM »

to expand on what Tom mentioned...

ibedonc has built a (still somewhat experimental) DC-DC converter with which he has powered a 130V, 13W CF lamp from a 16V, 123F supercapacitor bank. It operated with power from the caps from 12.5V down to 3V. Hopefully I remembered all those numbers correctly.

He's getting so enamoured with supercaps that he's changed his IRC nick to ibedonc_capman!

stop4stuff · « **Reply #9 on:** February 10, 2005, 10:19:25 AM »

More than likely, the 'capacitor' is a tiny rechargeable battery...

We've got several small RC cars that plug into a handset to recharge, I originally thought the cars had capacitors in them... but they turned out to be miniature nicads, 1/4" dia x 1/2" long.

Currently, I'm messing with caps and LEDs...

The cap bank is a mish mash of high value, low voltage caps totalling around 26,000 uF (micro farads).

The cap bank gets charged to 25v, I have a single 10,000 mcd white LED and resistor in a circuit with a 5v regulator. The circuit draws 9ma, and the caps power the LED for around 45 seconds... not bad... except the cap bank is approx 1" tall x 2" wide and 4" long and weighs more than a couple of 'D' cells.

So far tho, all of the caps have been free... found in PC power supplies and monitors.

having fun,

paul

troy · « **Reply #10 on:** February 10, 2005, 11:49:08 AM »

Actually, all of the farraday effect flashlights (like www.shakelight.com) use capacitors to drive the led. See for yourself on the website. Also, this particular flashlight is waterproof to 2,000 feet underwater. I love mine!

Best,

troy

iFred · « **Reply #11 on:** February 10, 2005, 03:06:02 PM »

what no one has mentioned so far is that; small batteries are capacitors basically. The origins are similar. The only major difference between caps and batts is the storage capacity of the potential charge. An example is that a battery can handle and store something like a couple million times more charge then a large capacitor. If a large cap could store 500,000 uf and be like 12" x 12" round then a batterie can store like 5,000,000 uf or more of charge in the size of 9 volt cell... that sort of idea I am trying to say.. In any case.. the cap is the ideal battery because there is no degradation of material or storage of the charge, whereas batts do have material problems. another issue is that you can discharge a cap without harm to the internals as many times as you want, but on a batt you can't do that, not rapidly in any case.

My two cents worth..

ibedonc · « **Reply #12 on:** February 10, 2005, 03:13:30 PM »

Well I could power that LED for days with my 123F bank

I am working on getting a 933F bank by next month

also supercaps are down to about 6 cents a Farad

ibedonc · « **Reply #13 on:** February 10, 2005, 03:15:07 PM »

I disagree

ibedonc · « **Reply #14 on:** February 10, 2005, 03:19:25 PM »

Question , how many people knew you could run a 13w 120vac CFL off 130vdc ?

they start at 90vdc

and it only was using @90vdc 10watts also no difference in brightness

TomW · « **Reply #15 on:** February 10, 2005, 04:30:27 PM »

Sorry, Fred but I have to disagree. Small batteries and caps are very very different.

Batteries store power in chemical reactions.

Capacitors store power as static charges.

Both store power but in very different ways.

Plus Don is working with capacitor banks in the hundreds of Farads range so i think he could jump start a truck with that bank.

Maybe Canada is different.

Accuracy is important.

Cheers.

TomW

tecker · « **Reply #16 on:** February 10, 2005, 06:00:10 PM »

Copper Bussmann ( power stor) seem to have the hottest brand for the money 1 farad 5 volt for around 6 bucks at Mouser chainem up and wala . The resistance is low with the Carbon Aerogel electrodes . Very exiting tech there.

richhagen · « **Reply #17 on:** February 10, 2005, 06:41:49 PM »

Just curious, how is your 123F bank constructed? Did you use Maxwell Boost caps or something else? Rich Hagen

newguy · « **Reply #18 on:** February 10, 2005, 07:01:45 PM »

i had a question about capacitors in the shakelights a while back and i did some research and well there are capacitors in disposable cameras that have flashes i wanted to run a led off one of these capacitors but i dont understand how to slow down all of the electricity so it all doesnt go at once does that make sense like a flash it is all used up and then you have to recharge the capacitor can you make it slower so if i hooked it up to a led it would work? well ive been shocked a couple times by the capacitor and curriosity got the best of me and i opened one of them up just wraps of metal that are separated by paper.

thanks i think

pyrocasto · « **Reply #19 on:** February 10, 2005, 07:41:07 PM »

I think I'm going to wait to start experimenting with caps, but they are very cool things.

And yes, you can make them by winding up some tin foil, seperated by saran wrap.

richhagen · « **Reply #20 on:** February 10, 2005, 08:02:29 PM »

I did not know this! I'll have to give this a try. Rich Hagen

Kevin L · « **Reply #21 on:** February 10, 2005, 08:23:43 PM »

Yes you can make your own condenser's but be VERY careful with them. They can discharge very quickly and shock the bejibberish out of you, expessially with 90 to 120 volts. If you want to limit the condenser's current draw place a 330 ohm resistor in series with the LED at 12 volts. This will give you a very slow drain on the condenser. Increase the resistance for longer voltage draw, reduce for a brighter LED. R=E/I with I target of 5 to 20mA. Have fun but be very careful, people have been killed by the high voltage condenser's in televisions of old.

ibedonc · « **Reply #22 on:** February 10, 2005, 08:35:28 PM »

here is my 123 Farad supercap , it is www.nesscap.com caps

when I get the 933@16v it will be made from 6 5000 Farad 2.7v caps

those are about 5 cents a farad

stop4stuff · « **Reply #23 on:** February 11, 2005, 12:35:08 AM »

use a resistor in series with the LED...

e.g. for 5v supply to a 50ma LED use a 100 ohm resistor to limit the current to 50ma. (5/0.05=100) The capacitor then drains more slowly.

Use the Ohm's Law equations V=I*R, I=V/R, R=V/I (V-volts, I-amps, R-resistance) to find the right resistor for different voltage & current values.

stop4stuff · « **Reply #24 on:** February 11, 2005, 12:36:41 AM »

thanks troy... i checked out the flashlight.com site they do use a small cap... anyone know of a UK supplier?

finnsawyer · « **Reply #25 on:** February 11, 2005, 10:00:37 AM »

Got any examples where it's used effectively?

ibedonc · « **Reply #26 on:** February 11, 2005, 10:33:56 AM »

http://www.fieldlines.com/comments/2005/2/10/11634/0951/22#22

iFred · « **Reply #27 on:** February 11, 2005, 11:06:50 AM »

Charge is charge, regardless if it's stored in a cap or a batt. Chemically or other means of storage. the point is the storage of charge and the amount- which is what I was saying... if your going to argue on semantics lets get that at least right, however I don't know how they measure things or do in the US! By all indications thus far, it's been a guessing/head game.

iFred · « **Reply #28 on:** February 11, 2005, 11:09:45 AM »

Got a schematic on this? would like to see it!

richhagen · « **Reply #29 on:** February 11, 2005, 11:53:19 AM »

I had looked at the Ness site, They were aiming to have a 5000Farad 3 volt model soon. Right now, they have that 2.7V 5000 Farad model. Did you get these direct from Ness, or through a supplier? I would love to get my hands on some of those to play with. I've had lots of fun with the little 15Farad bank, but bigger toys = more fun! If you are going to order a bunch more, maybe we could pool resources for a better price. Rich Hagen

ibedonc · « **Reply #30 on:** February 11, 2005, 01:58:32 PM »

those in the pic came out of audio caps off ebay , pay a lot for them could have had the 933 for what I paid for those , I now have contacted a supplier , and can get the 5000F 2.7v for $200 each

ibedonc · « **Reply #31 on:** February 11, 2005, 02:00:25 PM »

als0 the 100F 2.7v as on those boards are $7 each

TomW · « **Reply #32 on:** February 12, 2005, 12:22:31 AM »

ifred;

Sorry, but you tend to make broad statements that are just not accurate. Like this:

The only major difference between caps and batts is the storage capacity of the potential charge.

One other "major" difference would be that capacitors can absorb and release a charge much faster than a battery.

Another would be that capacitors do not suffer damage from extreme depth of discharge or repeated deep discharge over millions of cycles.

Both of these qualify as major differences in my estimation.

I think that it is important to be accurate but its not really worth arguing over since you tend to take it as some kind of personal attack. Some would call it semantics others may think of it as accuracy.

You seem to have acquired a following of folks who take your advice and it is only fair to them that you hold yourself to a higher standard when making absolute statements that may be referenced as factual.

I guess we can agree to disagree.

T

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Author Topic: capacitor storage (Read 738 times)