SuperCap 9V battery

9V batteries are often found in devices that aren’t used very often. If you use a NiCd rechargeable battery you may find it completely discharged by the time you need it. Capacitors on the other hand can maintain their charge for years. This circuit uses a 10F cap with a switching voltage regulator to increase the voltage from 2.3V to 9V. With a light load the cap will last up to 3 hours and once discharged it can be recharged in less than 20 seconds. Warning: PDF link.

[thanks nullset]

90 thoughts on “SuperCap 9V battery

  1. 10F! Whoa! I’m impressed with that alone… this is pretty sweet… now I’ve just gotta find something of mine that uses 9V batteries to try this out on!

  2. “The SuperCap can deliver a peak current of around 6 A, this equates to a lot of power (heat) dissipated in low resistance loads.”
    I guess you wouldn’t want to use your toungue to test one of these, like you would a normal 9V…

  3. I wonder why nothing like this is on the market? That seems ultra useful, especially for cameras, etc, where you may have access to electricity a lot but don’t want to wait hours for a charge.

  4. Cor, Elektor Electronics to the rescue! I remember reading them when I was a little nipper and they used to have lots of cool stuff like this in their magazines.
    Hmm, the article explains that one of the transisters is used as a zener to create an 8v value (the circuit produces around 8.5v).
    I’m tempted to adjust the circuit and create a dummy battery to make a super-cap based 3v cell to stick into my wireless optical mouse. That way, I don’t even have to worry about memory effects (quirk of NiCads) and even if it gets flat, it’ll charge in an instant!

  5. so, er , how about…

    take that basic idea of using it in a wireless mouse at 3v, and adding a kinetic charger, that that moving your mouse charges your mouse.

    might turn out to be a massive sized mouse…

    or convert the wheel , or better i guess, on a two wheeled mouse, make one wheel a charger, …

  6. This isn’t sold on the market because a AAA battery has 1000x the amp hours of this 10F supercapacitor. While a $5 10F supercapacitor is great for a capacitor, it is orders of magnitude too small for something like a camera. These caps are useful for a high peak power / low average power solar charged item as they have longer lifetime with less charge loss. See: http://electronics.howstuffworks.com/capacitor2.htm

  7. The article doesn’t talk about charging the cap. From the circuit it looks like you have to charge the cap leads. The circuit doesn’t support charging from the 9v terminals.

    bob: The voltage regulator limits the current available. The cap may be able to generate 6A, but the regulator will only do 1.5A (google the datasheet)

  8. If you put one of those tiny solar cells on the outside of a device with one of these inside, it could always be ready to go – as long as you didn’t keep it in a drawer.

    This is ultra-neat.

  9. Nice application of a supercap in such a way. But i dont like how it is done. A inductive switcher transistor pair with a zener clap is not energy efficient. (not to mention the quicent current usage).

    I would like something DC-DC up converter to upconvert the low voltage. It would increase the efficiency a lot, i have a setup here with a solar cell and a MAX756 to power a small microcontroller on 3.3Volts. The setup can power a white led for half a hour on a 2.5V 3.3Farad goldcap.

  10. rui maldonado: Yep, replace T3 with a 4-V zener and get a 4.5V supercap battery. I guess how appropriate it would be for your cheap digital camera would depend upon its battery compartment (determines the size of the caps you could use) and how much current it will draw.
    Crosius, alex, you could indeed charge it from a solar cell, but keep in mind that the total cell voltage static would have to be less than 2.3V at the cap terminals, or would have to at least 4V at the input of the charge regulator.

  11. #13 alex – google for “beam solarengine” for different ways of charging caps with solar cells … my understanding of supercaps had been that they weren’t good at discharging quickly, has this changed recently?

  12. rui maldonado: Yep, replace T3 with a 4-V zener and get a 4.5V supercap battery. I guess how appropriate it would be for your cheap digital camera would depend upon its battery compartment (determines the size of the caps you could use) and how much current it will draw.
    Crosius, alex, you could indeed charge it from a solar cell, but keep in mind that the total cell voltage static would have to be less than 2.3V at the cap terminals, or would have to at least 4V at the input of the charge regulator.

  13. hey steve! nice to see another beam/tilden fan around! I’m only just getting the time to really play with beam circuits, but I really like the mostly-analog nature of tilden’s designs.

  14. Ummmm… are you sure THAT cap is rated at 10 farad? Looks more like a 10 microfarad to me. If I am remembering right a 10 farad capacitor would be huge.

  15. jesse: Normally I would agree with you, but if you look at the cap in the picture, it clearly says 10F right on it. Then, if you had actually rtfa you would have noticed this part:

    “The circuit shown here uses a small outline supercap with a capacitance of ‘just’ 10F (yes, that’s 10,000,000uF!)”

  16. You can see the 10F rating in the picture – sure, a 10 farad capacitor would be huge, but these are 10 farad super-capacitors. I don’t know exactly how they are composed differently from normal capacitors but yes, this is a 10 Farad package.

  17. Yay for BEAM. It’s been a while since I’ve followed anything in the BEAM area, anything interesting happen since, oh say… ’99?

    Just to re-inforce others, that is definitely 10 farads, as stated in the article, I don’t think a 10 microfarad capacitor would even drive a single cycle of the oscillator (seeing as the other two caps are 100 uF each). I’m more excited about puting this idea into devices, than using it to replace batteries, personally. If you need to keep an MP3 player going for the 30 minute commute to school/work, and you forgot to charge it the night before, it’s much easier to let it charge for under a minute when you’re rushing to get out the door. Oh the possibilities.

  18. Guys, this 10F supercapacitor would run a mp3 player like my little muvo tx for less then 2 minutes on a single charge.

    AAA battery of 1.5V and 2800mAh = 4.2 Wh. A 10F supercap at 2.5V would be 0.00694 Wh. My Muvo runs for 14 hours on the AAA battery. 14 hours * 0.00694 Wh /4.2 Wh = 0.02315 hours or 1.4 minutes.

    Even a $25 50F supercap which is one of the most powerful ones would only give you 7 minutes of listening time. A camera would eat one of these up just as quick. Supercaps are great for beam, solar, leds etc but are a factors off to replace batteries in most applications. Supercaps are great for instant power (so fast charging/discharging) but not great for energy storage.

    The reason these supercaps are so small and light is that they use aerogel for the large amount of surface area.

    http://www.eepn.com/Locator/Products/ArticleID/28446/28446.html

  19. Unless your waste basket is the size of an AA battery, then yes… I’m staring at a 1 farad 5.5v super cap from allelectronics.com .78″ in diameter and .30″ thick. Not too huge at all.

  20. I Think that this is a wonderful thing, I mean you could have a flashlight that needed to charge for like no time, and could run for a couple hours

    Mike, I think your numbers for the amount of power from a AAA are off by a factor of 2. According to Energizer, the bottom level Energizer AAA is only 1250 mah. That is roughly one half, but my point being, these capacitors hold a lot more juice than youd think….

  21. “I wonder fi the gauss pistol could benefit from these gold-cap capacitators….”

    Actually, not really because the discharge time is in the seconds according to the article. Now if they made these with a much lower ESR…

  22. My number for AAA could be wrong so lets use 900mA instead of 2800mA. Point is thats 4 minutes of mp3 player time. The difference between a conventional battery and this 10F supercapacitor is on the order of 1000 times the capacity. Lets say I wasn’t half off but was 10 times off, that still is 100 times less capacity. I have supercapacitors here. For microcontrollers, leds, and pager motors they are great.

    According to this school physics site, a 10F supercapacitor will do over 30 seconds with a standard flashlight bulb. A couple hours is 7200 seconds by my calculation. Off by 240 times.

    http://www.djb.co.uk/SidePages/PhysicsPages/electricity.html

    (bottom of page)

  23. He says it will run a light load for 3 hours without a recharge… but that’s a pretty big exaggeration.
    He states the quiescent draw of the converter is 2ma at 2.3V, meaning a 4.6mW draw with no load, or 0.0046 joules per second.
    Energy stored in a capacitor = 0.5*C*Vsquared
    So stored energy = 0.5*10Farads*2.3*2.3 = 26.45 Joules.
    26.45 / 0.0046 = 5750 seconds of runtime assuming that the 100% of the capacitor’s energy is used (not likely).
    Meaning that after about 1.6 hours of this circuit powering absolutely NOTHING, the cap will have fully discharged. It’s a cute hack, but he should have used a proper low power dc-dc converter circuit.

  24. “I Think that this is a wonderful thing, I mean you could have a flashlight that needed to charge for like no time, and could run for a couple hours”

    You guys are greatly overestimating the power of these caps. A 10f 2.3v super cap stores about 25 joules; it could raise 1g of water by ~50F. That is also about the amount of energy used in the flash of a disposable camera.

    That 10f cap would power only a single LED for a few minutes, almost useless for a flashlight.

  25. Pocketbrain: Thanks! the compartiment is 3AAA cels sized. i wonder if 2 capacitors of lower size in series would have the same efect.
    I also wonder if it could take, let’s say, 4 ours of photos. normal bateries drain in 7days if not used to feed the internal memory, wich i dont use.

  26. oh gosh… i need autoupdate for firefox… again…
    well, as far as i have seen, it is almost useless unless used for emergency power for a mobile phone, for example.
    but really, has anyone experienced yet the autonomy of these cells?
    I would love to experiment, even in a flash light.

  27. Ugh, I just spent 15 minutes trying over an over to post a comment, is there a size limit that it is not telling me? It kept telling me rejecting my comment field.

  28. #26 and #27, I thought the same thing. 1 farad car audio caps are the size of soda cans or spraypaint cans… I did some googling and these supercapacitors are apparently different kind of thing, with different pluses/minuses.
    wiki:

    http://en.wikipedia.org/wiki/Supercapacitor

    http://en.wikipedia.org/wiki/Capacitor

    Also here’s some company page that mentions both:

    http://www.cap-xx.com/resources/reviews/strge_cmprsn.htm

    Unfortunately I couldn’t glean whether these supercapacitors make regular caps obsolete, or if they are just used for different things. I’m sure car audio buffs would prefer to use a tiny $5 unit that has ten times the storage as their $100 1farad caps if it were directly applicable… can anyone explain the difference?

  29. (not the same hans as in #44)

    afroman post #40: “he states the quiescent draw of the converter is 2ma at 2.3v, meaning a 4.6mw draw with no load, or 0.0046 joules per second.”

    Your mistake is that you take this number as a constant in the next calculation. As the voltage of the supercap decreases, so will the current (most probably), so the power (=U*I) will decrease even faster.

    With this underestimation you get 1.6 hours, so I think that if you take the diminishing power draw into account, 3h seems very plausible.

  30. Correct me if i’m wrong, but in beam, it merely uses the circuit for voltage detection and amplification to send the power to the motor. Basically, the solarcell charges the cap directly, and the rest of the circuitry is the trigger.

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