Got tired of replacing the lead-acid battery in a UPS (Uninterruptible Power Supply), so put together a super-capacitor array to go in its place.

Such units are now commercially available

Step 1: Super-Capacitor array

Started with six used 2600F 2.5V Maxwell super-capacitors that I found for $70 with postage and cross-bars included (from www.goldmine-elec.com, but they no longer stock them). The six are wired in series to allow for the voltages seen by a 12V battery; fortunately the array was found to be so well balanced by itself, that no extra circuitry was needed to ensure that no capacitor experienced an over-voltage. A UPS that trickle charges its battery will overcharge such an array, so a protective Zener diode would need to be added; the UPS I used it with did not have this problem, so there was no need for any extra components.
<p>Much appreciated, but they don't hold much energy, so chemical batteries might suit your application better.</p>
<p>I added a link to your Instructable in my comment section about this same idea that was told to me..</p><p>http://www.instructables.com/id/Wind-Generator-Design-4/</p>
<p>Intersting information!</p><p>I'm giving the super capacitors some serious thought for my solar and wind generators!</p>
<p>The energy in a capacitor is 0.5 C V^2, but I use half this as the UPS turns off before reaching zero volts; from this the Ah can be calculated. I picked capacitors that would physical fit. 30-60 amps should be easy for the units I used.</p>
<p>How did you figure the Ah equivalent and choose the CAPS? could something like this in a smaller package push 30-60 amps for a few seconds B4 having to be topped off?</p>
<p>sir i have a question where can i find that kind of capacitor i am here in philippines </p>
ebay; search for boostcap
<p>hello guys;</p><p>i have sun tracker <br>project, i wanted anyone can help me to know the specifications of my <br>supercapacitors ( my dc source voltage is 20 volt ) i need to have 12 volt and 1.2 amp from my supercapacitor</p><p>thanks</p>
Easily many KW if one wants; each capacitor is 2600F so the bank of 6 in series is 433 F
if they are hooked in series, you still get 2600F.
<p>No, you don't get 2600F. Check your physics textbook, or just listen to ashiekh, he really does know what he is talking about.</p>
<p>Give him a break, it's really counter intuitive. </p><p>The capacitance for series-connected capacitors is 1/Ctotal = 1/C1 + 1/C2 + 1/C3..., while the voltage goes Vtotal = V1 + V2 + V3...</p><p>The confusing part is that 1/C, to get the final capacitance you still have to invert it, so the final capacitance of the array is 2600 divided by 6.</p><p>Capacitance is not a direct measure of energy storage, it's a measure of the ability to store a charge. To get the total energy stored, you need to do a bit more math. C = joules / voltage squared, so a 2v capacitor at 2600 farads holds 5200 joules of energy, while a 12v capacitor at 433.3~ farads holds 31200 joules of energy, or 6 times the amount.</p>
It gets even tougher when one connects a source of voltage V to a discharged capacitor and only half the energy gets to the capacitor no matter how low is the resistance connecting the two.
<p>Er, C = 2 * joules / voltage squared</p><p>I got the calculation right though! :P</p>
Actually not so; but they do carry 6 time the energy<br><br>One way to see this is the energy is 0.5 C V^2, and 6 in series carry 6 time the voltage, that is one way to see that the overall capacitance is now 1/6 th
Please forgive my stupid comment, but when you say UPS, I am thinking United Postal Service. What does UPS mean hear?
I figured it out, Uninterupted Power supply, my bad. <br>
I have modified the document to clarify this; I hate acronyms.
how much power do they provide? and capacitance?.:D
In principle many kW is possible, but the UPS I use is only 500W; each capacitor is 2600F, so the series array is 433F
This is very nice idea. I am interest to negotiate with you about this idea, if it is possible please send me an email (mahyar.mashayekhi@gmail.com). <br>Thanks
Such UPS units are now commercially available <br>http://www.marathon-power.com/EN/UPSProducts/SupercapacitorUPS/SupercapacitorUPS.html
This is a wonderful idea, but have you tested how long it lasts in operation (how many minutes)? The reason is that the discharge curve of a battery and a capacitor are very different, so the UPS may shut down the discharge assuming that the &quot;battery&quot; is nearly dead when in fact the capacitors still hold plenty of juice. (Batteries have a long &quot;flat&quot; region in the voltage vs. discharge charge, whereas capacitors V declines linearly with the discharge Q.)
About 2 mins (as mentioned at the end); strictly the capacitor bank has 2Ah, but because the UPS shuts off early, it is only equivalent to 1Ah. I only intended it to carry across glitches, so 2 mins is more than I need; it would actually be closer to 3 mins but the UPS itself consumes about 75W<br><br>The real issue is when the UPS tests the 'battery' and in my case the capacitor array is seen to test as good, unless the UPS tests when I have a high load connected and then the UPS feels the voltage is falling faster than expected.
Can you elaborate how you charge this device? What kind of circuit you use? Im interested in something like this for home use.
The super capacitor array goes inside a UPS, so the UPS itself does the charging; I was fortunate enough to have a UPS with a lot of space inside.
It has been in service for over a year now holding up one computer and all the networking gear; as a result I have been able to retire all the other UPS units and don't so purchase anymore batteries. <br> Still, there are now lead acid batteries of claimed 12 year life http://www.csb-battery.com/english/01_product/02_detail.php?fid=19&amp;pid=120 but hopefully the capacitors will live even longer than this. <br> Then again, one anticipates a new generation of UPSs based on lithium technology.
great idea. Most power outages I've had last just a few seconds or cycle 2 or 3 times in just a few seconds. This would be perfect.
Nice concept :)

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