Picture of Ultracapacitor 3d Printed Flashlight
Using available parts and a 3d printer, I went from idea stage (sketch above) to a working device in one day. 

Printing and designing in 3d allows a designer to build a case and mechanical parts around whatever is available.  For example, I used an ultracapacitor from a Coleman Ultracap Screwdriver.  It was simple to design and print a hollow cylinder to accept the capacitor--this would have been a major challenge a year ago.
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Step 1:

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First I printed a cylinder, scavenged the capacitor and found an LED.

I used Autodesk 123d (free) to design the 3d parts. Files are available here:

Step 2:

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Next, I came up with a plan.  The LED is pretty directional, so I skipped building a reflector.  The light will run for hours and hours on a charge (and I charge it with a solar panel), so I omitted the on/off switch. Note the diode--that prevents the capacitor voltage from going backwards out onto the leads; you can clip the alligator leads together if you want after charging.

If you want to see how I regulate the incoming voltage, look at this instructable:

Step 3:

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Check to see that the capacitor fits into the cylinder.

Step 4:

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Drill a 1/8 inch diameter hole in the upper part of the cylinder (yes, I should have designed that in software, but I'm far from perfect).

Step 5:

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Slide the capacitor (minus any wires) into the cylinder.

Step 6:

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Add a 100 ohm resistor to the long lead of the LED (I soldered it).

Step 7:

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Add a red wire wrap wire to the other end of the resistor.

Step 8:

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Clip the surplus wire from the resistor and put a piece of heat shrinkable tubing over the exposed metal.

Step 9:

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Heat the tubing until it shrinks (I use the soldering iron to shrink the tube).

Step 10:

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Add blue wire wrap wire to the short leg of the LED.

Step 11:

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Clip the excess LED leg, add heat shrink and shrink the tubing.

Step 12:

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Push the wire end of the alligator clips through the hole in the cylinder.

Step 13:

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Push the LED leads through the cap (it's not really a reflector).
duggerpato1 year ago
Two questions I hope would be answered on the first or last step:
How long to charge it?
How long discharge?
MikeTheMaker (author)  duggerpato1 year ago
Two minutes of charge will give 12 hours of good light--that's the simple answer.

Now, the more complicated answer--it depends. From zero volts, with a one amp source; something like 15 minutes to charge. Five amps (circuit needs a higher current capacity diode for this) would do a total charge in three minutes. Because the led takes less current as the voltage declines, it will stay illuminated for days--so it can take a long time to totally discharge.

In practice, I charge it for two minutes (at a one amp rate) one time per day. It remains illuminated for 24 hours.

or use a joule thief in the design . an it could last 4 months.

Awesome. I think these are the future (part of it anyways). Thanks for responding, I know that you might have said it somewhere, I was just too lazy to look. Now, though, I want to make one.

Great job.
MikeTheMaker (author)  duggerpato1 year ago
Thank you!

I want to build one of these with a voltage regulator, switch, reflector and high speed charger (a real flashlight). You've fired me up enough to put it on my "list of projects to do" list.

Thanks for the encouragement :)
tiger125061 year ago
This is just a suggestion --

One could easily hold the body of the ultra capacitor, making the container somewhat superfluous. Seems that a PVC container would work just as well.

However, those alligator clips are remarkably obtuse; just hanging there.
I would put the power of the 3d printer to IMHO better use by creating a charging station for the flashlight.

Maybe two concentric rings on the bottom, so that you could set the flashlight into it in any orientation. That way, the contacts could be flat to the surface of the flashlight.

By the way, kudos on the short protection blocking diode, a great idea for this application!
MikeTheMaker (author)  tiger125061 year ago
Thanks--good suggestions!

I'm planning on building a flashlight (in the future) using the capacitor, a voltage regulator, reflector etc. (more like a real flashlight). I would use a purchasable capacitor instead of one from my junk bin--to make it more repeatable. I like your concentric rings idea for the charging base. I'm still playing with the idea of fast charge (5 amps or so)--any thoughts on how to make a good simple connection that can handle that without overheating?
I wouldn't worry about the charge current too much.
Voltage is low; resistance is very very low; so the power the charge contacts has to dissipate is very small.

If you want to be crazy about this:

The table there suggests that ~18 AWG should suffice.
I personally think this is overkill, but it gives you a ballpark.

Keep in mind that what really causes a wire to heat up is power dissipated, not amperage, so that P = V * I, where I is the amperage (5A in your example), and importantly, V is the drop *across the wire* which is dependent upon the resistance of the wire and the current. The resistance of the wire is dependent on the length and gauge of the wire. Your length is (very) short for those contact points.

I think that copper tape would work beautifully, to create contacts on the bottom of the flashlight.

Then the copper tape could make connection with your charging base merely by the weight of the flashlight holding the concentric tape circles against spring like contacts (which could just be 18 AWG solid wire that is "too long" forced up through holes in the base)

| | (base of flashlight shown in profile)
___ / \ ____ (visible bottom of charging station)
------/ \-------- (wire poking through bottom of charging station)


or ues a daul extruder to print in a dielectric plastic.

Where can one find a Ultracapasitor????
MikeTheMaker (author)  RyanWilliamTyler1 year ago has some--for example there is a 350 farad (at 2.7 volts) for $11.23 in quantities of one:

Or, has some really big ultracaps like a 3000 farad at 2.7 volts for about $76.00 in quantities of one: often has minimum ordering quantities . . . .
Thank you, but i have some 12v leds is there a ultracap that could supply 12 or more volts?
You could also rewire your LEDs in parallel. 12 volt LEDs are actually a resistor and a couple of LEDs in series. Put a voltmeter across one LED when you're putting 12V into the string, and you'll see what they actually take. Better yet, find out what their current rating is, and design something that supplies that current or less, so they last a long time.
MikeTheMaker (author)  RyanWilliamTyler1 year ago
You could put five 2.7 volt caps in series--but that gets costly.

I've never built a "joule thief," (try "joule thief" in instructables search box) but that might enable you to use one or two caps and power your 12 volt leds.
Thank you Very much
sparten111 year ago
wow a tube a cap an led. Really? I am just overwhelmed.
MikeTheMaker (author)  sparten111 year ago
There's really no accounting for what catches on--I've done a couple of rather involved and (to me) somewhat nifty things and received around 300 views.

I know you've done some really cool things--just know that you can win a grand prize with less than 1000 views (I have). Popularity and quality both count . . . I just submit anything that may be helpful to others (or that I just like) and let the chips fall where they may :)
nonono don't get me wrong I was not putting down your design sometimes the best things are the simplest. just the opposite. please don't misunderstand what i wrote. this is why I hate typing. it is the simplest project i love. my trouble is i over do it everytime i make anything. I voted for your project lol. so please don't feel like I am attacking it.

I am in no way doing that.

MikeTheMaker (author)  sparten111 year ago
Thanks--I love your radial engine and I voted for it!

I like to see "over done" projects--it indicates passion for the subject; keep it up.

I liked instructables better when the first step wasn't always: "fire up your $4,000 3D printer." People actually resorted to things like pvc! Shocker I know.
Ha, ha, ha.... There down to $600.00. :-) Jump for joy. Go

No, I have no affiliation or own a printrbot. I have a $1,300 dollar printer....
Yes, im getting very annoyed with all of these 3- d printed ibles This guy had to use a multi thousand dollar tool to make a tube? It seems to fly in the face of KISS keep it simple stupid , give me a mcgiver ible instead. I want to take my pocket knife some wire tape easily found materials and create stuff
Futurlec retails lots of small solar cells, assorted voltages and amperages, perfect for charging up caps like this.

In Australia - they are almost impossible to contact by any means - AND they don't say up front that the delivery takes like 3 or 4 weeks - which can drive you nuts if don't do your ordering wayyyyyyyyyyyyy in advance of starting your project / urgent replacement / repairs etc.

But they are reliable and do deliver - eventually.

However they are about the only retail supplier of very small solar "panels" ready to go, for small power supplies / chargers etc.

AND as far as home made chargers go, ONCE the car / deep cycle battery is fully charged up, a few of the 6V 16ma cells strung in series, makes for a great trickle charger - say 24V @ 16ma. It will never charge up discharged or partially flat battery but it will keep them charged up, and not boil them dry either - when left on the charge for years - with a monthly boil up (acid mixing) on the main charger.

0.5V 280mA Solar Cell
0.5V 830mA Solar Cell
1.0V 175mA Solar Cell
1.0V 415mA Solar Cell
1.5V 135mA Solar Cell
2.0V 45mA Solar Cell
2.0V 92mA Solar Cell
2.0V 200mA Solar Cell
2.0V 80mA Circular Solar Cell
3.0V 25mA Solar Cell
3.0V 45mA Solar Cell
4.0V 20mA Solar Cell
5.0V 100mA Solar Cell
6.0V 16mA Solar Cell
6.0V 60mA Solar Cell
9.0V 70mA Solar Cell
12.0V 80mA Solar Cell
luxstar1 year ago
What is the charging voltage from the solar panel?
MikeTheMaker (author)  luxstar1 year ago
The solar panel can deliver one amp at up to 15 volts dc--that's why I mentioned in step two a regulator to disconnect the charger when the voltage reaches about 5 volts.

At a one amp charge rate, it can take 10 to 15 minutes to bring the capacitor from zero to five volts--the capacitor looks almost like a short circuit to the charging source; thus the charging source (solar panel) voltage will collapse to essentially the capacitor voltage (the capacitor voltage--hence the charging source voltage--will slowly rise as amps are delivered to the capacitor).

It's sort of like charging a 12 volt car battery--your charger has to produce 13 volts to push any amps into the battery. If your battery charger could maintain 18 volts, it would push hundreds of amps into the car battery.
So in a pinch someone could use one of 1.5 amp versions of 7805 linear regulator with a heat sink. My experience has been that the regulator gets a little too hot so I have used an, I think 6 or 8 ohm power resistor at the input of the regulator when charging super-capacitors. I like DC to Dc converters better but the Murata one I use can’t handle the 15 -18 volts off the panel so I charge a car battery with the panel and charge the dc to dc converter off the battery. I mention this only because the people who use arduino are in the minority and linear regulators are cheap and easy.

MikeTheMaker (author)  luxstar1 year ago
Yes, there's a lot to be said for using 7805's, resistors and such. It's interesting to see how many different ways there are (considering available supplies and levels of interest) to accomplish the same task.

I've considered using the ATtiny (sort of a $1.50 minimal version of Arduino) to build a regulator--another "some day" task
hertzgamma2 years ago
Cool! What do you use to charge the capacitor up?

Just a tiny option to make it better - put a switch on the LED to hold the charge if you don't actually need to use the flashlight.
MikeTheMaker (author)  hertzgamma2 years ago
I use a solar panel--it would need a larger diode (more than 1 amp capacity) to charge it up really fast.

The switch is a good idea--the charge leaks down fairly fast, so a full charge is down noticeably in a day or two even with no load.
awesome! do you know the specs of the cap you used?
MikeTheMaker (author)  amandaghassaei2 years ago
I can't tell for sure--it's labeled "flashcell fc4." I think it is 180 farad at 5.4 volts (two 360 farad, 2.7 volt in series).