Ultracapacitors

[Leef]

Here's something I read today and wondered the obvious -- would ultracapacitors be a good power storage option for flashlights, esp. LED lights. Maybe the lower energy storage capacity is the hangup. Anyone know?
==============

Ultracapacitors are a newly developed technology positioned between the conventional capacitors and rechargeable batteries. Ultracapacitors offer a shift in thought, circumventing the battery scramble, and instead extracts greater efficiency from existing power sources. Ultracapacitors are free from the characteristic battery problems of limited cycle life, cold intolerance and critical charging rates. They are also environmentally friendly, help conserve energy, and enhance the performance and portability of consumer devices.

Ultracapacitors can be used to replace batteries in outdoor solar-lighting products. Although their energy capacity is not as great as that of batteries, it is enough to light areas in gardens, driveways, paths and mark roads. In solar lighting, the ultracapacitor has many advantages over batteries.

1. Ultracapacitors transfer electrical charges between conducting materials. They can be charged and discharged almost indefinitely. This removes the annoying maintenance problem.
2. Batteries work as a result of chemical reactions and can last ~1000 cycles.
3. The ultracapacitor can also be charged effectively regardless of weather conditions.

The ultracapacitor used in the SolarBrick, Solar Road Marker and GroundFlasher is called the EnegyCache. The EnergyCache is an improved version of the 'standard' ultracapacitor. The EnergyCache can hold twice as much charge in the same volume compared with a standard ultracapacitor. The EnergyCache is heavily protected worldwide by patents.


Ultracapacitors vs. Batteries for Solar Lighting Systems
Rechargeable batteries generate and consume electricity by chemical reaction. This leads to slower responses and the deterioration of performance over time. Usually the charge/discharge cycle is ~1,000 times at best. At this cycle rate, the rechargeable battery has to be replaced every 2-3 years. In addition, the operating temperature range of the rechargeable batteries is very narrow, from 0~45°C (32~113°F). Beyond this range, the performance of the rechargeable batteries drops rapidly. And so the proper working environment of the battery-based solar lighting system is limited. They require maintenance every 2-3 years and have a narrow working temperature range.

Ultracapacitors address the drawbacks of rechargeable batteries for solar based lighting systems. Utracapacitors are fast responding and show no deterioration of performance over time. The charge/discharge cycle of the ultracapacitor is more than 100,000 times. This translates into 273 years of continuous operation making it ideal for path lighting and buried traffic lighting. (One cycle of charge and discharge for solar lighting system is one day.)

 

[scott.cr]

This would probably be a good way to ignite lamps that need a high-energy/high-voltage pulse to get going, like HID, while using batteries that have high energy density/low peak current capability (like the Tadirans).

 

[Kram]

These do have some potential for providing energy storage for very low-level LED lighting. They indeed do have the advantages listed in your article. They suffer from some disadvantages, as well. Their power density (i.e. power storage vs. Volume) is very low compared to most batteries. They are pretty much the ultimate in terms of reliability, though.

These differ from some of the older large capacitors (physically very large in comparison) in that their voltages are typically much lower (say, around 5V) and are not really suitable for high current discharges.

Some of the better shake lights use these for storage of charge generated by the magnet moving through the coil. I have built homemade flashlights that use hand cranked stepper motors to charge the ultracaps which, in turn, feed one or two 5mm LEDs.

If your application does not require a lot of storage capacity, these are probably good choices. I think, though, that some further steps will need to happen in the technology before they gain wide acceptance as energy sources for LED lighting.

Mark

 

[chesterqw]

lol, i got some pictures of some super big caps...maybe i will go find them and upload them later

not safe for dial up users, srry unless someone resize them...

update: here they are! it seems that i found them

with the minimag 2aa incan as comparison.


see how dang thick and big they are?




from left to right, their labels.

don't have them now, they were picked up by my father as they were taking apart an obsolete machine they had and he kept it at some mysterious place as of now.

 

[jtr1962]

The best ultracapacitors are maybe 1/10 the energy density of NiMH and cost many times as much. However, the technology is in a huge state of flux. I personally feel within 5 years ultracapacitors will start to be competitive with chemical batteries. I think there's a good chance of them taking over entirely within a decade.

 

[andrewwynn]

what he said.. too early a tech to be useful.. it's what they use in the shakelights.. and they can barely run on the order of 1/10th of a watt.. consider this.. capacitors will only let out their current while the votlage is dropping.. they do not generate electricity like a battery.. i.e. a 1F cap can output 1A for 1sec.. but only by dropping from 4V to 3V.. meaning.. you'll get a brief blink of light as the cap discharges.

That said.. i sure have a lot of fun with my 4,000,000 µF (aka 4F) capacitor.. melts small wires really fast!

-awr

 

[chesterqw]

OMFG, how big is that 4F capacitor? 1m tall?

 

[andrewwynn]

nope about 10" tall, about 3" diameter. I use it for bench testing my 100W flashlight drivers.. since though they draw <10A running.. startup surges are more like 25A.. so i get the extra 15A from the 4F cap during the 1/3sec of the startup.. i have the vCap set to 1V+ over vLamp and it gets me a bit over 4 columbs of juice.. dividing by 1/3 sec i get 4x3 = 12A for 1/3 sec 'boost'.. the cap is completely drained during the 1/3sec startup of a 625 driver startup.. it actually doesn't quite reach full voltage, but the first 1/4 second is accurate and i'm able to bench-test with the power supply rather than having to use batteries like i did initially!

-awr

 

[chesterqw]

wow.... that BIG!

 

[Josey]

Ultracapacitors are going to be used in hybrid vehicles, and that market is big enough to drive a lot of research. So maybe in the not-to-distant future, we'll have applications for flashlights and solar systems.

 

[hotbeam]

OMFG, how big is that 4F capacitor? 1m tall?

The statement should be... "How small!!"

Let me see if I can get the 120F one out and take a pic

 

[NewBie]

External fuel tank, quick mod, removed NiMH cell inside, 27-Nov-2004.

2x runtime on car, instant recharge.

Yes, that is 10,000,000 microfarads.

Discussed on CPF around 2002 or so:
https://www.candlepowerforums.com/threads/8845

More info here:
http://candlepowerforums.com/vb/showthread.php?t=55044

 

[andrewwynn]

Oh.. i should point out.. 24V capacitor = my 4F cap... but nice on those tiny little caps and love the external fuel tank.

-awr

 

[tebore]

lol, i got some pictures of some super big caps...maybe i will go find them and upload them later ...

I've played with those kinds of caps in EE. Let me tell you it's not fun when someone from the last class leaves them charges and you accidentally finish the circuit with your arm. ZAP and it's numb for a few mins. After a few zaps it's kinda fun.

It's sort of an initiation for first year EEs.

 

[andrewwynn]

reminding me of labs with the megohm meters!.. the good ol analog ones with the crank to generate the 500V required...

1) close ckt (with a friend)
2) start turning slowly
3) how much can he or you take!?

oh.. the first time i figured out the charge cap and zap fun was when i was about 15 and took apart a camera flash.. i think they run about 200v

-awr

 

[scott.cr]

Those ain't no capacitors...

THIS is a capacitor! ;-)

http://205.243.100.155/frames/shrinkergallery.html

 

[mpteach]

I remember taking apart disposable cameras in high school and attaching wire prongs to the flash capacitor. hehe, everyone in my shop did it. cheap fun. They dont charge up nearly as fast as expensive camera flashes but theyre easy to take out and cheap. If you heard the whine of one charging you knew to move out of way

when charged the litttle neon status light blinked. I remember ane kid used one in his "build a better mousetrap" science project.

Future supercapcitors made out of carbon nanotubes will have energy densities less than but comparable to batteries. With fuel cells coming out i dont think there will be much of a need for rechargeable chemical batteries unless of course supercacitors cost a lot more

 

[andrewwynn]

scott.. thanks for sharing that.. what a fun little trip i just went on reading all about shrinking quarters.. i'm going to order one of my state of wisconsin.. very fun stuff.

all the fuel-cells i've seen even on the <10 yr horizon are high energy capacity and LOW power density.. i.e. they suck for high-power lights but work ok for low power lights.. there is a hydrogen fuel cell 1W LED flashlight already being produced.. runs for 24 hrs straight from a 15 minute charge of hydrogen... 24-WH.. impresseive but i want to pull that out in an hour not a day!

-awr

 

[billw]

You know, "Supercapacitor" usually refers to one of the new-technology (Double later, activated carbon, carbon aerogel, carbon nanotubes, etc) that have exceptionally high capacitance in a small size. Capacitors that are merely large or capable of discharging their energy in impressive ways (high voltage) need not apply.

There's a good article here: http://www.europhysicsnews.com/full/23/article2/article2.html
about 280x of 1000+F supercaps (about coke-can sized) deliver 50kW over 15s.

The supercaps are generally low voltage (2.5V), so you need to pay attention to get typical LED voltages, and you need a significant electronics infrastruction to develop the sort of midrange voltages (300V) that electric cars seem to like.

The energy in a capactor is 1/2 * C * V * V, so the typical 100uF 300V photoflash cap contains about 5J or energy, while the 10F 2.5V supercap that is about the same physical size stores 30 J (six times as much) (and at 2.5V, it's less likely to discharge through YOU to tragic or humerous effect.) The Coke-can sized 1500F caps store about 4500 J.

A Joule is a Watt-Second, and a 2500mAh 1.2V NiMH cell holds 10000+ Joules (if I did my math right), so supercaps have a long way to go before they'll match batteries in energy capacity. The combination of a high-power but low-capacity supercap and a high-capacity but low-power technology (battery or fuel cell) is particularly useful for a lot of applications (flashlights NOT amoung them!)

 

[jtr1962]

The combination of a high-power but low-capacity supercap and a high-capacity but low-power technology (battery or fuel cell) is particularly useful for a lot of applications (flashlights NOT amoung them!)

EVs especially. A supercapacitor will save the battery from current spikes during acceleration and regenerative braking. The net result is a far longer lasting battery. In fact, with supercaps the battery will easily last the life of a vehicle designed for a million miles. Another advantage of the high-power capabilities of supercaps is higher acceleration rates. Basically you can end up with traction-limited acceleration rates from a dead start all the way to top speed. In other words, 0 to 120 mph in maybe 6 seconds. :rock: