Flashlight Without Batteries--from the Book, "Haywired"




About: I am an author and a maker. My current project is Santa's Shop. I'm working on a science fiction type book--more later. @EngineerRigsby

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

First, solder a wire from the (+) on one capacitor to the (-) on the other capacitor.

Step 2: 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 (-).

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

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

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

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

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

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

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

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

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

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

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

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

Step 15: 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

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

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

Place electrical tape over the on/off switch wires.

Step 19: Glue LED Holder

Glue the LED holder into the flashlight body.

Step 20: Form Reflector

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

Step 21: 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

Plug a 3-volt DC power supply, (+) tip, into the back for three minutes. Remove the power supply and enjoy your new flashlight.

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    140 Discussions


    10 years ago on Introduction

    I just saw the Tecate website. The caps the have are balanced they say so there is no need for external regulation. Did I get that right? Am I to understand there is no need for current limiting or is the circuit just to protect the caps. If you get a big enough cap bank and a wind generator you could power your house without batteries. Or maybe from Lightening Bolts!! YEAH THATS IT!! I LIKE LIGHTENING!!!!!!!!!!!!

    5 replies

    Reply 10 years ago on Introduction

    Ha! When I was running Squid Labs, prior to Instructables, we once got a proposal to design lightning-powered electricity plants. The potential client said that he was sure there was a tremendous amount of energy in each lightning bolt, and that if we could just figure out a way to capture and distribute that energy, we could both be rich (he was willing to split all future profits related to his "idea" in return for our work actually developing the system).


    Reply 10 years ago on Introduction

    Ben Franklin (never known as Mr. Safety) came up with a system to let him know about upcoming electrical storms (so he could go out and play). Known as Franklin's Bells, this is probably not advisable around buildings or people you ever want to see again. However, using an old tube type computer monitor (or your old analog tube tv), you can simulate Mr. Franklin's work. Look at
    to see how this can work. Search "Franklins Bells" for more information.


    Reply 10 years ago on Introduction

    There is a battery pile that was made in the 1700's. It had a brass ball hanging on a bar at the top from a silk thread down between 2 brass bells that would just ring all the time. Well, it's still ringing today and it is part of a collection belonging to Yale University. Cool Huh ?


    Reply 3 years ago

    I think you are thinking of the Oxford Electric Bell running off of two Zamboni Pile batteries. The bell was started in 1840.

    Try Digikey--here's one that will work


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


    5 years ago

    Nice job


    5 years ago on Step 22

    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.


    It's good for an hour or so at reasonable brightness--but it will continue to produce light for 24 hours or more.


    7 years ago on Introduction

    done.. Here is the link to the 2600 farad flashlight instructable:


    1 reply

    Reply 7 years ago on Introduction

    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!