Introduction: Water Powered Flashlight (v2)

Picture of Water Powered Flashlight (v2)

Batteries are too mainstream, let's make Water Powered ones! This is my newer version of my previous flashlight project, this time we are using pennies (literally)! The flashlight works by using water as its electrolytes.

Getting Some Inspiration From My Vacation:

I spent a third of my summer hopping on the pristine islands of Palawan. We wake-up early everyday (4:30am). We rented a boat for the tour and one thing that I've noticed, the boatman used a flashlight to prepare the boat every morning, same for the fishermen who wakes-up early. I stared at the sea for quite some time and I remembered, these men can power their flashlights using the saltwater around them.

Is It Really Powered By Water?

Th internet currently has beer batteries, lemon batteries, potato batteries and water batteries. All of these batteries are powered by the same thing - the Redox reaction between copper and zinc or aluminum. The fluid (or potato) is just the electrolyte, and any solution with dissolved ions - which is basically any solution in water at all - will serve as an electrolyte. Some chemists will react bad to this title, some aren't bothered at all. Let's just call it the galvanic battery from now on.


The project is under documentation, probably done by tomorrow. I rushed it for the Green Design contest.

Step 1: Parts & Materials

Picture of Parts & Materials

Common Household Parts:

- A Sheet Of Aluminum Foil

- Wet Wipes (Tissue Paper)

- 10 American Pennies

- Hook-up Wire


Electronic Parts (for Joule Thief):

- 2N3904 General Purpose NPN Transistor

- Toroidal Core (from old CFL bulbs)

- 1k Ohm Resistor (¼W)

- Four 5mm White LEDs


Tools & Equipment:

- Leatherman Multitool

- 30W Soldering Iron

- Digital Multmeter

- Hot Glue Gun

Step 2: Cut Round Traces of Aluminum Foil

Picture of Cut Round Traces of Aluminum Foil

For homemade batteries, aluminum and zinc works as a good cathode. On my last project (the v1), we used a zinc strip, it was a bad idea to use it since not all hobbyists has them. Aluminum is the best alternative, every one has them at home, problem solved! :)

Step 3: Cut a Bath of Wet Wipes (Tissue Paper)

Picture of Cut a Bath of Wet Wipes (Tissue Paper)

Ok, first it's time do decide whether I should use regular tissue paper or wet-wipes. What's the difference? Well tissue paper tears easily and becomes mushy when it gets wet. Wet-wipes on the other hand is made to withstand tearing, it's almost like a cloth. I say choose wet-wipes!

Done deciding? Find a sharp pair of shears, the Leatherman's scissor is sharp enough, then cut multiple traces of wet-wipes. Use the coin as your guideline.

Step 4: Stack Two Plies of Tissue Paper

Picture of Stack Two Plies of Tissue Paper

Please follow the pattern correctly, otherwise the project would not work. I stacked two plies of wet-wipes on top of my penny. Why two? It will hold more water.

Step 5: Next, Stack a Sheet of Foil

Picture of Next, Stack a Sheet of Foil

Now, stack the aluminum foil on top of the tissue paper.

Step 6: Repeat Until You 10 Cells

Picture of Repeat Until You 10 Cells

Repeat this process until you have created 10 of these cells.

Step 7: Glue the Cells Together

Picture of Glue the Cells Together

I glued my 10 cell galvanic battery to prevent the cells from separation.

Step 8: Test It

Picture of Test It

My readings showed the my 10 cell penny battery produces 5.1 volts. That's a lot of power, coming from a galvanic battery.

Step 9: Drill the Recycled Enclosure

Picture of Drill the Recycled Enclosure

The electrolyte needs an entrance and exit. Too much fluid inside would lead a short.

Step 10: Make Plastic Dividers

Picture of Make Plastic Dividers

Like all batteries, your penny battery needs dividers. Luckily my recycled enclosure has ridges, those ridges can hold small credit card cut-outs. I used my expired timezone card :)

Step 11: Time to Get Salty!

Picture of Time to Get Salty!

Galvanic batteries love salt! Salt increases the voltage output. Sprinkle salt over the pennies then set aside the excess.

Step 12: Add a Switch

Picture of Add a Switch

I used a push button toggle switch. Kindly glue it in series with your penny battery.

Step 13: Install the LEDs

Picture of Install the LEDs

Cut a fraction of perfboard then solder four LEDs in parallel.

Step 14: Build a Joule Thief Inverter

Picture of Build a Joule Thief Inverter

It's up to you to build a joule thief. The Penny battery has enough voltage to run the LEDs. Adding a joule thief keeps the voltage uniform even when the penny battery needs replenishment.


Step 15: Waterproof the Electronics

Picture of Waterproof the Electronics

The easiest way of waterproofing the electronics is by applying a thick blob of hot glue around it.

Step 16: Put the Cover Back On

Picture of Put the Cover Back On

Put the cover back on and you are ready to go!

Thank you for your time! :D


AllysonA4 (author)2017-12-12

Hi how much did you spend to create that one?

NicoleManalili (author)2017-08-05

Are there any other alternatives rather than American pennies?

Alden LukeR (author)2017-04-18

Hi, i am planning on building something similar for my gr10 science expo. Is it nescesary for the joule thief?

Romy HamprayP (author)2017-02-18

Would a Copper-nickel-zinc alloy work? Thats what a philippine 25 cent is made up of.

HashamG (author)2016-09-24

you cheated Angelo i saw the hold button of the multimeter turned on .And without any electrolyte these cells can not work

Rajesh Barlota (author)2016-08-30

How can we make a call phone chager by useing water and salt

SahibS1 (author)2016-03-25

Please help I want to make a bigger project like this . Like a 5W led powered by water or solar energy . I have to help my poor neighbours as they don't have an electric connection. E-mail me at

Medelis (author)SahibS12016-04-11

I'll Show You - How drinking water can deliver electric power ... Free Geen Energy without poison or toxins

This battery generates electric power out of Tap Water (drinking water or any similar liquid).... its small and powerful

battery will work about 3 hours (you can always refill water - make it work again)

Medelis made it! (author)2016-04-11

I'll Show You - How drinking water can deliver electric power ... Free Geen Energy without poison or toxins

This battery generates electric power out of Tap Water (drinking water or any similar liquid).... its small and powerful

battery will work about 3 hours (you can always refill water - make it work again)

SahibS1 (author)2016-03-24

Is it necessary to use Joule THIEF

SahibS1 (author)2016-03-22

I live in India can I use Indian coin

MargarethA1 (author)2016-01-14

IF I try 25 centavos from Philippines ... could it be work?? please reply .. I used this as our project for saving environment in our science fair.. I know that this is not my invention so? I get your idea So thank you :D

bob8898 (author)2015-06-04

You didn't really specify the stacking order for battery: Is it aluminum + wetWipes + penny + aluminum + wetWipes + penny +...

Helga_Magick (author)bob88982016-01-11

I tried mine with Philippine 10-centavo coins and the order goes like this: coin, wet wipes (tissue) and aluminum, coin, wet wipes, aluminum. In the voltaic pile, Alesandro Volta designed the battery like this.

Yonatan24 (author)2015-12-24

Which glue did you use to glue the cells together? It probably doesn't matter but I'm just wondering

yaasvanthkuhan987 (author)2015-12-14

Can I use more than 10 pennies ?

bob8898 (author)2015-06-08

HOW THE *bleep* do you get 5 volts out of that?????? I can onlly get 0.20 volts!!!! WHY????????????????????????????????????????????????????????????

aangara (author)bob88982015-11-12

your battery must be shorting , if the electrolytes mix from the 10cells it will work as a single battery and also if you didn't do it right voltage will further be reduced (battery emf reduces when anode-anode or cathode-cathode is connected)

jkoi (author)2015-09-23

Whats the use of water if penny+aluminum+wet wipes could produce electricity already? Do we need to refill water always?

aangara (author)jkoi2015-11-12

once the ions in the electrolyte are used up I.e battery dead , recharge it by adding water

jkoi (author)2015-09-23

This project was nice, it give up certain ideas on building something that is useful for others. How about a motorbicyle, motorcyle, or cars that powered by this same thing that could help the community or rather lamp post?

LoknathS (author)2015-08-25

How long will the light last,and is this one time use,

alcurb (author)2015-08-24


Ninjayewolf (author)2015-08-22

Do you have a recorded video of you constructing the flashlight, installing LEDs, joule thief, hook-up wires, etc? :(

preethiks121 (author)2015-08-21

hey what is the role of the water if it uses pennies as its battery?

SidA2 (author)2015-08-11

If you file down one side of the penny, it reveals the zinc core. Then you can just stack penny, wipe, penny, wipe. It can take a while to sand or file down 10 pennies, but I did it and it gave me the same results. Just make sure to keep the pennies all oriented in one direction like keeping the zinc side down all the time.

fxtimaxlwt (author)2015-08-07

can we use peso coin?

fxtimaxlwt (author)fxtimaxlwt2015-08-07

pls reply :(

mihir.sahu.355 (author)2015-06-09

can i use copper strip insted of penny

nam2002 (author)2014-10-23

Will indian rupee coins work???? plz reply fast

ASCAS (author)nam20022014-10-23

I'm not sure. Do your research. Look if they are copper and zinc based coins.

bob8898 (author)ASCAS2015-06-04

can the standard amercinan pennies be soldered?

MattS17 (author)2015-04-01

This looks like a great experiment for my son to do for his scout Super NOVA award. I have a few questions. What type of wire are you using? Your part list says "hookup wire". What do you do mean by that? And how are you connecting the wire to the pennies?

akshay.d21 (author)MattS172015-04-16

Hookup wire is also called as single strand wire. Available at any local electronics shop or hobby shop.

You can solder the wires to the Copper pennies. :)

bob8898 (author)akshay.d212015-06-04

there zinc

bob8898 (author)2015-06-04

is it possible just to make the battery and put it in a different flashlight? (I don't have any white... wait nevermind! i ahve 3.)

bob8898 (author)2015-06-04

so do i need the jule theif?

bob8898 (author)2015-06-04

what type of glue?

bob8898 (author)2015-06-04

will my coil wrapping skills / wire type effect the joule theif?

AbhinavS4 (author)2015-01-14

please explain the wiring instead of saying install the led and why is there only one wire running out of your battery

AbhinavS4 (author)2015-01-14

please explain the wiring instead of saying install the led and why is there only one wire running out of your battery

ohmygab (author)2014-11-25

Great job! I sent you a pm regarding this project! Thanks!

april.virtucio.3 (author)2014-11-19

do we need to remove the plastic casing of the toroid from the old CFL bulb? thanks in advance!

roshen (author)2014-11-18

can I use copper instead of pennies

Himers (author)2014-11-14

This is awesome!!!

michaelgc (author)2014-08-21

Great project, this would be cool to use as a middle school stem project.

roberts1 (author)2014-08-08

couldnt you just sand the zinc off one side of the penny to the zinc underneath.

regardless i enjoyed your concept.

mondee07 (author)2014-08-01

Can I use this concept for our project. I would like to combine your emergency lamp and the battery in this instructable. I'll call it Glenda. Inspired by the recent typhoon. Haha

joaqi823 (author)2014-07-28

Do you know any Philippine coin that can substitute the penniless

joaqi823 (author)2014-07-28

Do you know how many ampiers this produces because my multimeter my multimeter is broken and only measures volts

About This Instructable




Bio: Hi I'm Angelo! I am a 18 y/o college sophomore taking my majors in BS-ECE at the DLSU. I use my course as ... More »
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