400 Farad Super Capacitor Flashlight. Build This One. It's Easy.




Introduction: 400 Farad Super Capacitor Flashlight. Build This One. It's Easy.

About: Hello

Wouldn’t you like to have a flashlight that does not need batteries that will last a lifetime? Wouldn’t it be great if you didn’t have to shake it every few minutes to keep it lit up? Then what you need is a super capacitor flashlight.

Step 1:

Step 2:

The pen light is easy to take apart. The gray plastic part with the lens unscrews. Pull off the black ring. Pull the board out of the white plastic tube. The black wire on the board will be connected to a metal contact on the side of the white tube. Cut the wire at that contact.

Step 3:

I bought the plastic boxes from Radio Shack. You will also need 2 on/off switches and 2 RCA jacks. And you will need a 400 farad capacitor which is available from Future Electronics.



2.7 V 400 F, 60 °C Electric Double Layer Supercap

Mfr Part#:


Currently $19.98 each.

By the way, I decided to go with a jack for the LEDs so I can change/upgrade LEDS without re-wiring.

My favorites are 2 piranha leds (shown in the first picture) and a 10mm multi-chip.

The piranhas are available here:


I bought the multi-chip from Goldmine Electronics.


Sometimes they have them and sometimes they don’t. They have them now. In the future this link may not work from time to time. This type is available from other distributors but I like this one. Also, I checked this one with a microscope and verified that it is a multi-chip because I could see there were more than 2 little wires going to the chip. Goldmine Electronics says this is a 220000 MCD LED. Could be but I doubt it.

Since this flashlight puts out over 20 milliamps to the LED when fully charged, powering 2 leds or a multi-chip led is a good idea.


Step 4:

Here is the circuit. It’s easy.

The run time with 2 piranha LEDS on low is 6 hours.

The run time with the multi-chip on high is 2 hours.

Your results may vary.

You can squeeze a little more run time out of it by:

1. Charge the capacitor to 2.7 instead of 2.5 like I did.

2. Use a larger resistance for the high / low part of the circuit.

I have also run a laser diode with this circuit.

Step 5:

You will need to charge your flashlight. Here is the instructable for the DC to DC converter circuit for charging super capacitors:


It's 93% efficient.  It could be useful to power up / charge other things.

Or you can make a linear regulator circuit:


I prefer the DC to DC converter. It does not get hot and it is more efficient.

Step 6:

Here is another flashlight.  It has two of the 400 farad capacitors. Also there are 2 inputs for charging the capacitors and a switch to switch over from one capacitor to the other. So when you are using the flashlight and it starts to get a little dim you can switch over to the other one. It’s like having a spare gas tank.

Big Ray is shown with the multi-chip LED. The connection for the led is an RCA jack so LEDS are interchangeable.

So there you have it. The capacitor is rated for 500,000 charge / recharge cycles. LEDs typically are rated for at least 50,000 hours if used within normal operating parameters.

You know what that means. Years of fun and no batteries.

If you are interested in an easier flashlight project for long run time emergency lighting try this one:


It’s an easy 10 minute modification.

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    5 Discussions


    7 years ago on Introduction


    I have been running tests with different motors of various sizes.  I have a test set up with a large wheel with a crank/handle on it to step up the rpms on the motors I have tested.  It is easy to light up leds with motors but charging a large super-capacitor is a lot harder.  My goal is to get 1 hour of light for 2 minutes of cranking.  I have only one motor (out of the 20 or so I have collected over the years) that is big enough to meet the goal but it is too big to be portable.  I have given the half-hearted effort to making a generator but that has not met my goal.  For now I am not pursuing it since the overall goal was to have a way to have lighting off the grid and without batteries for an extended period of time if necessary.  That goal can easily be met by having:

     A solar panel as small as 5 watts

    A junky old car battery (does not have to be good enough to start a car).

    A 12 or 14 volt linear regulator (LM7812, LM7814)

    A charging circuit for this flashlight.

    And a couple of super capacitor flashlights.

    So since I have the great big motor in case there is a problem with the solar panel / car battery set up, I’m still prepared.  If I do pursue the generator thing in the future I have my eye on this one to connect to a bycicle:


    $49.00 here:


    I Think I will only be needing 2- 3 amps at under 6 volts.  After 2-3 minutes on the bike I get on with my life.  Thanks for the comment Drakekay.


    7 years ago on Introduction

    By the way if you don’t want to build a supercapaitor flashlight but you would like to own one, here is a review of the Lightstorm CL1 flashlight with a crank:


    It looks like a good option if you don’t mind winding every 20 minutes. The high beam appears to be very bright. It is a mechanical device with gears so it will wear out over time if used often. Perhaps owning both is the best of both worlds.


    7 years ago on Introduction

    Hey Luxstar, Greet concept. :D Why not add a hand turned rotor with magnets attached to it, encased in a coiled stator to charge that cap?


    7 years ago on Introduction

    Note: When I ordered my capacitors I accidentally clicked on the 2.5 volt capacitor instead of the 2.7 volt. They make both. So I am stuck charging at 2.5 volts. Don’t make the same mistake I did.