# Let's learn about Super Capacitors! (A Practical Guide To Super Capacitors)

Hi Instructables Community!

CHECK OUT OUR SUPER CAPACITOR FLASHLIGHT KICKSTARTER CAMPAIGN:
http://www.kickstarter.com/projects/172204344/the-forever-rechargeable-talking-super-capacitor-f?ref=live

Thanks for looking at my instructable!  This instructable will be a little bit shorter than some of my others, and it will be written from the perspective of a technician, not an engineer.  This instructable will be followed with similar super capacitor related instructables.  I'm not going to blast super capacitor noobies with a ton of flashy math.  However, I will be providing links to sites where math can be found for those of you who are interested.  I want to keep this document as practical as possible. There are some fun videos in STEP#8 and some links to my hobby electronics stores in STEP#9.  For those of you who don't know much about super capacitors, here is a little bit of fun theory:

THEORY:
Super capacitors act like any other kind of capacitor, only they can store tremendous amounts of energy.  Many capacitors that you'd have seen in audio circuits have capacitances such as 470uf or 680uf (micro farads).  Capacitors used in high frequency RF applications can be as small as 1pf (pico farad).  The farad is a measure of capacitance (or storage capacity).  They are often used in filtering applications, coupling or decoupling applications, or AC-DC smooting applications (there are some large caps in your standard AC-DC power supply that acts to smooth out the ripple on the line).

Super capacitors can be used in solar power applications, battery back-up applications, battery applications, flash-light applications, etc.  Aside from the fact that the super capacitor can be charged very quickly due to their low internal resistance, which is known as ESR, but they can just as quickly be discharged.  Batteries contain harmful chemicals, and die over time.  If you handle your super capacitors carefully, you will die before they do...Seriously!  Howver, there are rules...

Super capacitors do not give off gas like lead acid batteries, but they cannot store as much power either.  You can place capacitors in series or in parallel to either up the maximum charge voltage, or total capacitorance.  We will talk about this later.

Really, there is a lot to be said about capacitors, and you're not going to want to spend your entire day listing to me, so let's get down to the basics.  You can go fourth and choose which tabs you;re interested in.   Here is a video just for fun of me starting my car with super capacitors!
•

 1-40 of 71 Next »

hello sir,

we are working in a solar car project,our problm is:-

1.we have to ride the car with solar power without using batteries,for a 50-70(meters),the car weighs 250kg(max).

we r using 3 solar panels and we r getting approx. 470w from it.

is it possible to drive d car with that power.

if NO, for initial torque we r going to use super capacitor,is it possible.....

please give d super capacitor values,nor possible suggestions......

i will be very much thankfull to u .....................

13 days ago

If you're actually getting 470w from your panels, that's about 2/3rds of a horsepower, With correct gearing it shouldn't be any problem... Supercaps could help it start up quickly though

flipbook1 month ago

I want to use a supercapacitor in a circuit charged by an inductor and magnet (energy harvesting coil). How can I limit the charging voltage coming out of the coil so it won't blow the supercapcitor (a diode to ground? or something) and what happens if I keep adding more current after it's fully charged (but still at the rated voltage)? Thanks for a very informative ible.

15 days ago

This is not something you need to worry about . Although for a microsecond your coil will generate high voltage this is too fleeting to cause harm ( unless it's the size of a toaster) . The high voltage is immediately dissipated, it's better to think in terms of power . Just connect the coil with a diode in series to the cap, but don't overcharge, put a voltmeter across the cap , or a single white LED, which will light up at around 2.4V.. if it's a moderately sized coil it will take quite a while to charge up.

15 days ago

......An improvement on my above reply.... The coil will not generate high voltage when connected to an empty capacitor, it's the same as if you were to short the coil, voltage low, current 'high'... the coil only produces high voltage on open circuit... the power can't get out , so 'pressure ' builds until it can, (so to speak)...but as the capacitor fills up you could reach high voltage, limited only by how leaky the capacitor is, and the efficiency of the diode....hope that helps.

Nice informative instructable.

Mlagma3 months ago
Nice tutorial! I've been looking around the web for some practical information about super capacitors, and this seems to be the best source so far.

I have a few questions though (which I haven't been able to find the answers to on any site thus far).

I'm working on a project that requires a temporary backup power source, and the simplest and most cost effective method seems to be through the use of super capacitors. The idea is that the caps will provide power to a microcontroller which can detect the transition to backup power. From there, it will enter a low power state (low current display, RTC, backup registers, and backup SRAM).

The current consumption is rather low, probably 100mA at most at 3.3V. So here's my questions:

A capacitor basically stores energy via an electric field, which is created by charges accumulating on separated plates (generalizing here). The voltage across these plates is proportional to the amount of charge stored and so forth. As a battery discharges, the voltage remains relatively constant until it's nearly depleted. But because of how capacitors store energy, the loss of charge will result in a loss of voltage. So if I use super capacitors as a power source, is there any rule of thumb to predict how long the voltage will remain roughly around 3.3V? (I probably could work it out by hand, but this seems rather application dependent).

Also, do you recommend any current protection when using these caps? In my project, everything is primarily digital, so it'll only draw however much current is needed, but I'm a little concerned just based on how quickly capacitors can discharge versus a regulated power source.
foxwoodfarm7 months ago

When salvaging components from circuit boards are all capacitors that look like the ones pictured at the top of this page super capacitors. If not how can I tell a super capacitor when I see one?

3 months ago

There is not much difference really between run of the mill electrolytic caps and supercaps. A rule of thumb is one farad and up, i.e. 1F. 100,000 uF is 0.1F

In all likelihood the caps you salvage are not supercaps but nevertheless useful components.

foxwoodfarm3 months ago

I want to use a super cap or several, to light a half dozen LEDS. I am going to charge the caps with small solar cells. My question is how many Farads do I need to keep the lights going for 5 or 6 hours.

3 months ago

If you don't do to the math you will have to experiment. The math involves knowing the current and voltage of your LEDs, the power of your solar panel, and of course capacitors discharge exponentially (not anything like a battery) so perhaps you should experiment with small devices first.

Dhruv.doggii5 months ago

which size battery can i use for charging a 450 volts and 100uf(m) capcitor.

help me plz

3 months ago

Anything up to a 450 volt battery will charge your capacitor to the voltage of your battery, but only 100uf.

iglierseke16 months ago

5 months ago

Yes you can.

Your circuit will only charge it to the voltage that it is supplied with though...

the 10V cap will only store max 6.3V that the origanal Cap would have stored.

KenC76 months ago

I've looked at this circuit (balancing circuit show above) about 30 times now, and I really don't get a few things. First, assuming the circuit as drawn, how did Johnson come up with the two resistors that go along with the reference diodes? I've looked up the datasheet for those diodes, run the values through some calculators, and I get minimum shunt resistor values more like 900Ω instead of the 33kΩ he used. I'm assuming the high values go along with the 10kΩ resistor to drop the current for the comparator, but I can't get the number he used.

Next, do you really need three voltage references for this? Couldn't you use just the first one, since they all seem to be generating the same reference voltage? Clearly you need all three comparators/op amps, but the references are just there to set a lower value to compare to the voltage divider output for each comparison. (I'll be using 5.5v supercaps, and I have a 5v rail available - I can't see why I'd need the voltage references at all. Just tie the negative values into the 5v rail.)

Finally, given the low voltages and currents involved here, is there some reason he couldn't just choose a suitable zener diode to balance these supercaps? 2.4V 1W? Or if you're feeling risky, 2.7V 1W? A 2.7V zener should start to breakdown just below 2.7, right? With 300mA max current, it doesn't seem like you'd be risking your wattage limits. I'm thinking about 5.1V, 5W zeners for my circuit, and wondering if I really need the comparators and MOSFETs at all. (30V max, 500mA max, coming from a bike hub generator, so there won't be a big in-rush issue.) This is a terrific circuit for more serious stuff, but it seems like serious overkill for the circuit that's there.

hello sir,

we are working in a solar car project,our problm is:-

1.we have to ride the car with solar power without using batteries,for a 50-70(meters),the car weighs 250kg(max).

we r using 3 solar panels and we r getting approx. 470w from it.

is it possible to drive d car with that power.

if NO, for initial torque we r going to use super capacitor,is it possible.....

please give d super capacitor values,nor possible suggestions......

i will be very much thankfull to u .....................

hello sir,

we are working in a solar car project,our problm is:-

1.we have to ride the car with solar power without using batteries,for a 50-70(meters),the car weighs 250kg(max).

we r using 3 solar panels and we r getting approx. 470w from it.

is it possible to drive d car with that power.

if NO, for initial torque we r going to use super capacitor,is it possible.....

please give d super capacitor values,nor possible suggestions......

i will be very much thankfull to u .....................

athjustfreera7 months ago
Hi sir good day!!
Sir we are now working with our project, and we have some problem regarding it. Our project is a solar panel and we can only produce 500mv with a current of 1mA. Will we be able to store enough voltage and current on a capacitor for our converter to work which have a minimum input of .9V and 100mA? What rating of capacitor is necessary if possible?

By the way sir thank you very much for you're instructables, it was helpful.
AnkushD8 months ago

Is it possible to charge a supercacitor to store energy beyond the voltage of the input source. For example if I hook up a 1.5V battery to the supercapacitor with a diode in between to prevent discharge can the supercapcitor drain the battery and store the charge from it to 2V? I have tried and it does not work. I am trying to use the supercacpitor to store energy and then use it for light an LED, but the input source I have goes to a max of 1V. What circuit should I be using/modifying. Any thoughts.

7 months ago

The supercapacitor voltage will only go as high as your input source. That is to say if you have a 1V input source you will only be able to charge the super cap up to 1V. You can use a boost converter to make your input source 2 V. For example, the MCP1640 allows you to set your output to the needed voltage using a couple of external resistors. Note that you will also need an inductor.

testsegu8 months ago

hi i want buy the super capacitor charger where can i get it thanks

mediabeing9 months ago

It's hard to take the copy seriously when you write 'listening' as 'listing'.

You want us to take you seriously, right? Care enough to do it right.
Thanks.

EngineeringShock (author)  mediabeing9 months ago

A few spelling mistakes? Really? This instructable may not be perfect, but it has been helpful to many. Instructables liked it enough to feature it. Take me seriously or don't. I didn't ask for you to read it. I didn't ask for your approval. I spent many, many hours of my own time on this, so please, if you have nothing kind to offer, then please don't post on my instructables.

sghosh219 months ago

These videos are in one word "AWESOME"

arjunmenon11 months ago

to sustain a circuit requiring 300ma almost for 10 hrs, how much charge should a supercapacitor store.

11 months ago

i meant 5v 300ma.

jorgeacano11 months ago

Errata, example 2: The total capacitance in series is: CT=1/(1/C1+1/C2), so then, CT=1/(1/200 + 1/1000) = 166.66f , Not 1200f.

Errol19511 year ago

can I use a 400V capacitor in a 5volt circuit using a 5 volt zener to limit to voltage going into the capacitor if i can how will it effect the cap thanks

Conductor will go red??? Then discharging takes how much time??? And isn't it supposed to make a BIG spark, I do this with my 450v 220uF cap..
foxwoodfarm2 years ago
I salvage components from my retired electronic devices. How can I identify any of the capacitors are "super capacitors"?
1 year ago

Very high farads in a (relatively) small package. you probably wont find them. The big ones are mostly used as regenerative breaking buffers in large vehicles, sometimes the little ones are used as backup power sources for small ICs (they keep the clock from resetting if the device looses power)

freezier1 year ago

Update: there is now a mosfet that has been engineered just to balance Super Capacitors. They are made by Advanced Linear Devices... google SAB mosfet to learn more. I just ordered a couple from digikey to try out on my bank...

bent16152 years ago
This message is for Rahul Nema. I am trying to do something similar but Engineering guy said it is was not going to be easy and very costly. His advice was to buy batteries. NOW with the advent to the super capacitor out for some time, please let me know what you came up with .. if you did. In my case I have only 1.4kw solar and I dont want lead batteries to gas up the area. You can contact me at my mail at bent1615 at gmail if you like. hope to hear from you. TIA
Ben
1 year ago
Hi.
For the queries about using supercaps as replacements for batteries, the maths for capacitors to current is pretty simple. You only need two formulae:
(1) CV=Q where C=capacity in farads, V = voltage, Q= charge on capacitor in Coulombs.

(2) Q=It where I=current in Amps, t= time in seconds.

(3) From (1) and (2) we get CV=It

So, if you have a 1F supercap charged to 5v and take 1amp from it, it will last for 5 seconds.

A 100F supercap at 10v will supply 5A for 100x10/5 secs= 200 seconds or 3 mins roughly.

Compare this to a AA 1.25v 2Ah rechargeable. By multiplying the voltage by the current by the time in seconds we can find out how many Coulombs this is equivalent to. This will provide a total of 1.25x2x3600 Coulombs of charge = 9000 Coulombs.

Using equation (1) (C=Q/V) we can see that this is equivalent to a 9000/1.25=7200F supercap. In fact, because of the maths, you can work out the battery equivalent in supercaps by multiplying the battery Ah by 3600 if the supercap and battery are used at the same voltage.

A standard 12v 40Ah lead acid battery is equivalent to a 144,000F 12v supercap.

As you can see, there are significant cost issues in using supercaps as replacements for high capacity uses when replacing even small batteries, although they do obviously at this moment in time have their uses for low power/short surges and quick charge situations. There are also issues regarding supercap voltage. This will droop linearly with the amount of charge taken, unlike a battery which stays pretty stable until near the end of its charge. This means the supercaps will require some sort of voltage stabilisation circuitry in addition to the supercaps.

They will develop over time though, as all new technology does and there is huge potential in the future for high capacity battery replacement but it's probably still quite a way off.

I hope this helps.
mofassair2 years ago
Sir,
I am working on your project.
But I cannot find LMP2231, MPV30UN, LM385 in my local market. Problem is I am from bangladesh and its difficult to bring those parts from USA.
So, if you can give any alternative of those parts.
jbaker222 years ago
Would you expect a damaged 3000F ultracap to be reliable still if they have 60-80% of their original capacity?
SteveGerber2 years ago
I'm thinking about setting up a minimal solar power system to provide power to a very tiny off-grid house and I'm trying to figure out if there might be a way to make it work without using a battery bank.  I realize that this setup would not provide any power after the sun goes down but the fridge I list below is designed to hold it's coldness through the night.  My idea is to hook about 200 watts of solar panel(s) to a super capacitor and then run a super efficient chest fridge and a washing machine directly off the solar panels through the capacitor. The idea is that the capacitor would help to manage the start up power surge that the electric motors cause and would also smooth out and regulate the power. The fridge would be something like the SunDanzer BFR105.  I would hope to use an energy efficient washing machine too but I'm not sure what the amperage draw would be.  There is one web site here that gives some idea of the typical  power draw during various washing cycles.

Some questions I have are:

1.) Would a 20 Farad capacitor like this be suitable for this application or would I need a larger size?

2.) Am I understanding correctly that a 250 watt solar panel like this  with a Maximum Power Point Voltage Vmpp of 30.7 V would put out a voltage that is too high for the capacitor but that two 100 watt panels like this  in parallel with a Voltage at Maximum Power Point Vmpp of 17.7 would work correctly?

3.) Do you have any idea what would happen if the washing machine attempts to draw more watts for too long a period than are available?  On the pedal power web site it shows that the washing machine draws up to 820 watts at certain times during spin cycles but at other times the draw is much lower.  If not enough watts would be available would the machine simply run more slowly?  It seems that the wash cycle would be ok but that the spin cycle might quickly run the capacitor down.