Picture of Flashlight Without Batteries--from the book, "Haywired"
In this project, you will make a flashlight that works without batteries. Even more amazing, you can recharge it in three minutes and it will run for more than 24 hours. Because the ultra capacitors can be recharged thousands of times, you may save the environment from ever receiving an old flashlight in the trash system.

This project is from my book Haywired

Click here to order a copy from the Chicago Review Press.

Parts List

(2) 220 farad capacitors, www.digikey.com, #589-1013-nd
Insulated wire, black and red
LED, high brightness, www.jameco.com, #217525
12" x 12" acrylic plastic sheet, 1/8" thick
Permanent marker
(2) C clamps
1/4" jack, Radio Shack, #374-280
Metallic tape
SPST rocker switch, Radio Shack, #275-693
Electrical Tape

Tools List

Wire cutters
Soldering Iron
Scoring knife (for plastic)
Single-hole paper punch
3-volt DC power supply--700 milliamp
1/4", 1/16", and 3/4" drill bits
Metal straightedge

Step 1: Put capacitors in series

Picture of Put capacitors in series
First, solder a wire from the (+) on one capacitor to the (-) on the other capacitor.

Step 2: Solder wire to (+)

Picture of Solder wire to (+)
Solder a 4-inch length of red wire to the unused (+) terminal on the capacitor. You will call this capacitor wire (+).

Step 3: Solder wire to (-).

Picture of Solder wire to (-).
Solder a 2-inch length of black wire to the unused (-) terminal on the capacitor. You will call this capacitor wire (-).

Step 4: Correct method to cut plastic

Picture of Correct method to cut plastic
Next cut the 1/8-inch plastic sheet for the flashlight case. Generally, this is accomplished by scoring the plastic, then breaking it along scored lines. But first, mark the plastic with a marker, then use the C clamp to hold a metal straight-edge next to the mark. Then use the tip of a scoring knife (usually sold next to the plastic sheets) to create a fine groove in the plastic along the line you marked.

Step 5: Scoring Plastic

Picture of Scoring Plastic
Using the scoring edge (not the knife tip) pull the knife along the fine line several times until you create a groove. The plastic can now be snapped along the score line. Practice this method a few times until you master the technique.

Step 6: Start the case

Picture of Start the case
Now you're ready to build your flashlight case. First, cut out three 1 1/4 x 7 inch pieces of plastic and glue them together with epoxy. This is the flashlight body.

Step 7: Install jack

Picture of Install jack
Cut a plastic piece 1 1/4 inches by 1 1/2 inches. Drill a 1/4-inch hole and insert the 1/4-inch jack. Hold the jack with one hand (to prevent it from rotating) while threading the nut and washer.

Step 8: Add wires to jack

Picture of Add wires to jack
Solder a 2-inch-long black wire to the end of the jack near the tab. Solder a 3-inch-long red wire to the other side of the jack (away from the tab).

Step 9: Attach jack to capacitor

Picture of Attach jack to capacitor
Solder the red wire from the jack to the capacitor (+). Solder the black wire from the jack to capacitor (-). These wires form the path that will be used to charge the capacitors.

Step 10: Prepare for LED

Picture of Prepare for LED
Cut a piece of plastic, 1 x 1 1/4 inches. Drill two 1/16-inch holes in the center, side by side, the same distance apart as the leads on the LED. Cut a piece of metallic tape, 1 x 1 1/4 inches. Punch a hole in the center of this tape using a hole punch.

Step 11: Place reflector and LED

Picture of Place reflector and LED
Remove the paper backing from the tape and fasten the tape to the plastic. This is part of the reflector for the flashlight. Insert the LED leads through the holes.

Step 12: On Off switch

Picture of On Off switch
Cut a piece of plastic 7 inches by 1 1/4 inches. Drill a 3/4 inch hole 2 1/4 inches from the end. This is the plastic switch holder. Press the on/off switch through the hole and secure it by threading the switch's plastic nut.

Step 13: Attach wire to switch

Picture of Attach wire to switch
Solder one end of a 6-inch length of black wire to one end of the capacitor (-). Solder the other end to the on/off switch.

Step 14: Capacitor (+) to LED

Picture of Capacitor (+) to LED
Solder the wire from capacitor (+) to the long lead of the LED.

Step 15: LED to on/off switch

Picture of LED to on/off switch
Cut a 2-inch length of red wire. Solder one end to the short lead on the LED. Solder the other end to the on/off switch.

Step 16: Glue jack piece to flashlight body

Picture of Glue jack piece to flashlight body
When the switch is on, power will flow from capacitor (+) through the LED, through the switch, back to capacitor (-). This will cause the LED to light up. Carefully place the capacitors and the jack into the flashlight body. Glue the jack piece onto the end of the flashlight body.

Step 17: Separated jack and capacitor

Picture of Separated jack and capacitor
Cut a 1 by 3/4 inch piece of plastic. Insert it into the flashlight body, between the jack and the capacitor. This will prevent the capacitor from sliding into the jack; thus avoiding a potential short circuit

Step 18: Cover on/off switch wires

Picture of Cover on/off switch wires
Place electrical tape over the on/off switch wires.

Step 19: Glue LED holder

Picture of Glue LED holder
Glue the LED holder into the flashlight body.

Step 20: Form reflector

Picture of Form reflector
Place metallic tape inside the flashlight body and on the plastic switch holder to form the reflector.

Step 21: Finish assembly

Picture of Finish assembly
Glue the plastic switch holder to the flashlight body. Cut a 1 1/2 x 1 1/4 inch piece of plastic for the lens. Glue the lens in front of the LED.

Step 22: Charge and use

Picture of Charge and use
Plug a 3-volt DC power supply, (+) tip, into the back for three minutes. Remove the power supply and enjoy your new flashlight.
1-40 of 133Next »

I really want to try this project! But can someone please tell me where to get the capacitors?!?

MikeTheMaker (author)  BowtieMeerkats1 year ago

Try Digikey--here's one that will work


I've been searching everywhere for these. Thank you so much! They should work similarly correct?
MikeTheMaker (author)  BowtieMeerkats1 year ago

They should be similar--may be a different physical size. They have more capacity, so should cause the light to illuminate longer.

Ok great! Thanks!

gluvit1 year ago
Nice job
wobbler1 year ago
Comprehensive instructions, but you are lucky to find the LED not burning out if you don't use a current limiting resistor in series with it. LEDs are very sensitive to over-voltage. The cheap battery LED lights you get often don't have a dropper resistor to save money but they rely on the internal resistance of the battery limiting the current. The problem here for others copying this design is that they could have an LED which needs less than 3v and, because the supercap can deliver large currents, it will blow the LED. There are lots of sites which will let you put in the driving voltage, the LED voltage and the LED current and give you the value of the current limiter resistor.

It might also be a good idea to use a current limiting resistor in the charging circuit also, to limit the current when the capacitor is empty in order to not fuse or blow up the PSU. An uncharged supercap is effectively the same a s a short circuit across the PSU which may blow up an unprotected or fused PSU. Charging from batteries, this is less of a problem due to their internal resistance.
agginamp2 years ago
Hey Guys! I made a drawing of it:

Schmidty162 years ago
how long does it last
MikeTheMaker (author)  Schmidty162 years ago
It's good for an hour or so at reasonable brightness--but it will continue to produce light for 24 hours or more.
cool man i like
viswamtvs3 years ago
i tried it
very nice
luxstar3 years ago
done.. Here is the link to the 2600 farad flashlight instructable:

MikeTheMaker (author)  luxstar3 years ago
Anyone interested in supercapacitor projects should look at this--and follow the links to suppliers. Luxstar has pointed out the best price for big caps that I have heard of!
luxstar3 years ago
I recently made a supercapacitor flashlight that requires no batteries. I charge it off of a 5 watt solar panel. The larger capacitors of this type are usally quite expensive but the $10.00 2600 farad capacitors are back for now (on home page of Goldmine-Elec plus others on boost cap page).
Here is the link plus the link to instructions, diagrams, and pictures of the flashlight.
MikeTheMaker (author)  luxstar3 years ago
Great resource! Thanks for sharing.
Working on adding the pictures
fwjs286 years ago
that looks pretty sweet....how long does the light work?
MikeTheMaker (author)  fwjs286 years ago
It shines brightly for two or three hours--but shines enough to be a night light for 36 hours or longer.
wow! thats awesome
luxstar fwjs283 years ago
I recently made a supercapacitor flashlight that requires no batteries. I charge it off of a 5 watt solar panel. The larger capacitors of this type are usally quite expensive but the $10.00 2600 farad capacitors are back for now (on home page of Goldmine-Elec plus others on boost cap page).
Here is the link plus the link to instructions, diagrams, and pictures of the flashlight.
Holy ****, you can get 220F capacitors? I kind of want to get five so I can have a kilofarad- there's a certain geek pride in breaking a new unit like the terabyte or the petaflop :) I make a 220F capacitor at 3V almost exactly 10,000J, which is 3,333 amp seconds or about 925 mAh. Given an average NiMH AAA battery has 900mAh, that makes one of these capacitors roughly equivalent to two NiMH AAA batteries! And it recharges in a couple of minutes! I need to get a couple of these for my MP3 player... we live in the future :)
fwjs28 PKM6 years ago
Whoa...that sounded like geek jargon flying at me at over 9,700,300.284 miles a milisecond!...lol...so im just gonna shake my head up and down and act like i understand...
PKM fwjs286 years ago
Hehehe sorry, I have a tendency to work out stuff like this to make it clearer in my own head (but possibly less clear in everyone else's :P). If you ignore the "show your working" part in the middle, I just figured out that each one of these capacitors can hold the same amount of energy as two rechargeable AAA batteries, which is pretty impressive for a capacitor.

yeah ignore the bit about kilofarads as well..
MikeTheMaker (author)  PKM6 years ago
Try out this place:
I purchased some really large capacitors for another project.
BC-454 years ago
How do you charge a capacitor that is rated at 350 farad 2.7 volts any one know cause i don't know is it's safe to charge it wiht a 15 volt power supply.
D5quar35 years ago
 Digikey stopped selling the ultra capacitors anywhere else I can find them

www.electroniclessons.com will take you to an ebay store that sells all sorts of them. DC-DC boosters as well.
Kasaron5 years ago
Seems like this needs to be hooked up to an induction generator, to really make it an emergency flashlight.

Anyone know if I have to use an AC/DC rectifier to sort out the charge?
To charge this circuit using even a good DC crank would take a heck of a long time, and it would result in an extremely sore arm =s
LazarusTree6 years ago
This circuit seems potentially very dangerous to me. I think there needs to be at least one diode between the voltage input and the capacitors to limit electron flow in one direction and with a voltage rating less than the capacitors.

On what you have here, if you reverse the voltage and/or exceed the voltage rating on the caps and this is a potential bomb that will send shards of plastic flying everywhere.

If his input voltage is 3VDC, then he's not going to over-charge the caps. I'd be more concerned for the input source with no limiting resistors in series with the caps. That's a good way of destroying your wall wart,
Are you suggesting that in any circuits it is better to use a diode between the voltage source and the capacitors? if we should add diodes to prevent from any accidents in a circuit in what all conditions and with what all components should we do that? It would be very kind of you to reply me............
MikeTheMaker (author)  shobanaelango5 years ago
If you choose to Use a diode, it should have a higher voltage rating than the capacitors and it should be able to handle as much current as your power supply provides. If you power supply has diodes on the output (and no capacitors beyond the diodes), then you probably don't need an additional diode. Although these capacitors store a lot of energy (for a capacitor), it's less energy than a "aaa" battery.
BC-454 years ago
So how is run time determined by ferrad like if i have a 100uF cap it will last less and if i use 100F it will last longer is these right?
MikeTheMaker (author)  BC-454 years ago
Yes, the larger the amount of farads, the longer it will last.

If you can determine the "ohm equivalent" of your load, then the formula, T=RC where T=time (in seconds), R= resistance in ohms and C=capacitance in farads; then T will be approximately how long your capacitors will supply some power to your load. For example, if your load is 1000 ohms and you are using a 1000 microfarad capacitor (1000 X .001 =1) then the power will last about 1 second. This is the reason that you need capacitors with farads (not microfarads) of capacity to power anything for very long.
Claudio_MV4 years ago
Hi, can I make this work with 2 1000 microfarad 200wv capacitors?
MikeTheMaker (author)  Claudio_MV4 years ago
The capacitors I suggested (in series) are the equivalent of one hundred ten million microfarads--so your capacitors are about 1/10000 of the storage.

That being said, what you have will work--but only for a few seconds.
alexanderm4 years ago
Great Instructable! Thank you for sharing it!
Hopefully, it inspires people to buy your book!

i couldn't help but to think how cool it would be to add some solar cells in that clear case, though!
such a great idea or i called invention
it so easy and educational ha....
1-40 of 133Next »