The EXTREMELY EASY VERSION of the Super Capacitor Flash Light

Introduction: The EXTREMELY EASY VERSION of the Super Capacitor Flash Light

About: Hi there! My name is Patrick, and I am an electronics engineering technician who works full time as a lab tech, and part time as an electronics engineer/salesman. I own an ebay store, and two websites, which …

Hi everyone!


I recently wrote an instructable on how to make a super capacitor flashlight, but I made it too complicated, and it employed a microcontroller, which many people don't have the means to program.  So this one only employs a power supply, a dollar store flashlight, two super capacitors, a switch and a current limiting resistor.  I designed this so that my girlfriend (Who has no electronics background) could put it together, which she did.  This is her super capacitor flash light based on my design.   If you want to modify this design, you only need to follow the very basic arithmetic that I'll be providing.  Otherwise, all you need are the parts listed in the parts section (All of which can be found on ebay).  See the final product of this very basic flashlight below, then follow on to the circuit theory.  Because we're using super capacitors, THIS FLASHLIGHT CAN BE CHARGED 100,000s OF TIMES!

If you like this instructable, please don't be shy!  Comment and rate it!  This super capacitor flashlight will last for 100,000s of charges, which makes it SO COOL!  Below is a video of the final product.

For those of you who are interested, the below video is the final product from my more complicated super capacitor flashlight.  I have an instructable for this, so check out my profile if you're interested.  It can be found here:

Step 1: Parts List + Tools Required + Notes

For this design, I will be using the following parts:
1)   2x 50 farad 2.7v super capacitors (Found on ebay for very reasonable prices.  Less than $10)
2)   1x Switch.  It needs to be a switch capable of supporting more than 2.5A at 5v.   You can also consider using the default switch circuitry of your dollar store flash light. Switches can be found on ebay for pennies.
3)   1x 2.5 Ohm 10W power resistor (Found on ebay for a couple of bucks)
4)   1x 5v 3A wall transformer.  (Found on ebay for a couple of bucks)
5)   1x dollar store LED flashlight (Found at any dollar store for a buck or two)  The bigger the flashlight, the better.  It makes for easier placement of the components.

Here is a list of the tools that I used:

1) Soldering Iron
2) Lead Solder (Tin/Silver will work just as well)
3) A Hand Drill
4) A Hot Glue Gun

1) Make sure that the flashlight housing is large enough to fit all of your parts, or you're going to have trouble. 
2) DO NOT BUY a bulb flashlight.  They consume too much current.  Look for a white LED flashlight.  It will last much longer each charge.

Step 2: The Circuit

As promised, this circuit is very simple. 

The positive lead of the 5v power supply is connected  through a terminal block (Or a DC Jack if you have one) to one side of the 2.5 Ohm 10W power resistor.   The terminal block or jack is used so that you can connect and disconnect the wall transformer at any time.   The resistor is used to limit the current from the power supply to the capacitors.  Without this, you may very well harm your power supply.  When charging, this resistor will get hot, but it won't take long to charge your capacitor flashlight using this value, so you're not going to have to worry too much.  However, when mounting this resistor in the flashlight, try to keep it insulated from the flashlight plastic.

On the other side of the resistor, you'll see that I have placed two series super capacitors on the line.  These capacitors will charge to 5v when the power supply is plugged in.  Make sure that you place them in the right way.  If you reverse your super capacitors, they will be severely damaged when charging.    If you want, you can use a large value of resistor, such as a  5 Ohm 5 Watt resistor, 10 Ohm 2.5 Watt resistor, or a 20 Ohm 1.25 Watt resistor.

In this case, I wanted to charge my capacitor bank very quickly.  Since the power supply can handle 5 volts at 3 Amperes of current, I want to charge my capacitors at 2..5 amperes.  Ohm's law came into play when I did the design calculations.  Follow below.
Charge Voltage = 5V
Charge Current = 2.5A
Resistance = Voltage divided by Current  (5V / 2.5A) = 2.5 Ohms

Now, we need to determine the power rating for our resistor
Power = Voltage multiplied by Current (5V x 2.5A = 10 Watts)
Therefore, if we want to charge our bank at 2.5A at 5V, we need a 2.5 Ohm 10 Watt current limiting resistor.

The switch is used to connect power that is stored on the super caps to the LED flashlight module that you've taken out of your dollar store flashlight.  This can be turned on during charging, and can be turned on after the charge has been disconnected.
When the switch is off, no power reaches the LED flashlight, and the power on the capacitors will remain stored. 

Step 3: Assembly Notes

You can really go about this in your own way, but here is how my girlfriend chose to put this device together.  She wrote this section.

1) I soldered the circuit together.  I then made sure to add long wires in between each component so that placing each component into the flashlight would be easy.  I also made sure that the wires from the jack to the resistor, and from the resistor to the capacitors was thick and well insulated.  This is because the wires will be hot termporarily during charge.

2) I utilized the on board switch on the flash light to apply/disconnect power from the capacitors to the LED flash light head.

3) I glued the DC back in the battery bank section, so that I could remove the battery cover and plug in my transformer.  It just makes the device look more professional.

4) I glued the capacitors together length wise, and placed them in the shaft of the flashlight.  I then added some glue in the shaft to secure them in place.  

5) I placed my resistor at the top of the shaft.

7) I put the flash light back together.

Then, we both had a beer to celebrate this new fast-charging super capacitor flash light!

Step 4: Considerations

Now that you know how to build it, you can easily modify it, and make it your own.  I'm an electronics guy, and my mechanical handy work can be heavily improved on.  If you make your own, please make sure to post a picture of the final product in the comments section.

If you're looking for someone to vote for in the instructables MAKE IT GLOW challenge contest, or the MAD SCIENCE FAIR Contest, please consider my instructable =)

If you're interested in super capacitors, see my practical guide to super capacitors here:

Thanks everyone!

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    5 years ago

    It's relatively easy to get an idea of the run time of these types
    of circuits. The energy stored in a capacitor is 0.5xCxVsquared
    (CxVxV/2). The capacitance is in farads, the energy in joules.

    So the energy in this case is a maximum of 0.5x100(total capacitance)x2.7x2.7=364.5joules.

    how do we decide the runtime? We divide the power by the power of the
    LEDs in watts and that gives us the runtime in seconds. So, if we are
    using a 1W array, the run time will be 364.5seconds, or roughly 6
    minutes. If we used a 3W array it would be only 2minutes.

    However, although this is the calculated time, it will vary in reality based on two conflicting issues:

    unless we use a sophisticated dc-dc converter, not all of the energy
    will be used. If the LEDs fail to light below e.g.80 of the voltage, we
    could only get 20% of the runtime. Capacitors, unlike batteries, don't
    store all the power and then have a fairly stable voltage until the
    battery is almost empty, but decay away proportionately to the current
    taken, so the voltage is continuously dropping.

    Secondly, working
    against the first is that an LED doesn't take the same current as the
    voltage drops. It continues to take less and less so therefore the
    runtime gets extended. The cost though is that the LEDs will fade
    continuously before finally disappearing. This is why some old design
    LED torches without a DC-DC converter seemed to have long quoted battery
    lives, but were actually unusable by the end in terms of any useful
    light output.

    So, I said it was relatively easy to calculate the
    runtime? It is, but the actual runtime will vary quite dramatically
    depending on how you define "runtime". The calculated runtime is correct
    for full brightness but it may be much longer for a "useable"

    In comparison, if you want to work out how many joules
    a typical battery holds, simply multiply the Ah rating by the voltage
    by 3600 (to convert to seconds). Thus, an AA rechargeable 1.2v battery
    with 1000mAH holds 1.2x1x3600=4320 joules, which is roughly 12x the
    energy stored in these caps.

    That's one of the reasons
    batteries are used in appliances. Although supercaps have many
    advantages in terms of recharge speed and potential current delivery and
    may be the preferred storage mechanism of the future, they
    unfortunately currently fall short in terms of economic power storage.


    Capacitors Energy

    Batteries Energy

    • The Inventor •

    Pretty simple circuit it is, but I still have some questions:

    1-does this circuit FULLY CHARGE the capacitors ( like they'll make a big spark when shorted )?

    2-what does make a bigger spark with fast emptying: higher voltage cap or higher capacitance cap?

    3-is it possible to fully charge these super capacitors using disposable camera circuit?

    4-what it I used a combination of capacitors that'll make 0.00086 farad with 400v instead of the super capacitors used here?

    Thank you.


    9 years ago on Step 2

    OK, this is nice and 'simple', but what am I missing?

    Your resistance calculation seems to say that 5 divided by 2.5 is 2.5 - not 2.

    Your power calculation appears to claim that 5 multiplied by 2.5 equals 10, instead of 12.5.