Water Powered Flashlight




Introduction: Water Powered Flashlight

About: Hi I'm Angelo (TechBulder)! I am an engineering major in BS-ECE at the DLSU. I use my course as an inspiration for making my current projects! I've been posting projects here ever since I was 10. I also run a …
Batteries are too mainstream, let's make Water Powered ones! The DIY flashlight never runs out of batteries, water is all around us and will never run out. One of today's causes of pollution is the improper disposal of batteries containing heavy metals such as lead and mercury. The answer, using water as electrolyte!

Imagine, running wall clocks for 6-12 months with water, you'll never need to leave your house just to buy batteries and there's no need to recharge them. What could be more convenient than replenishing your batteries with tap water? :D

The flashlight runs 30mins continuously with tap water and 2 hours with saltwater. Not bad for a single celled prototype :D This thing also works well with calculators, clocks & radios Remember, adding a second cell triples the glow and lighting time!

How Does It Work?
This is a type of battery called the "Galvanic Cell", having 2 different types of metals and is connected by a salt bridge. It works like your typical battery but uses water as its electrolyte. If you want to read more about how batteries work "click here" The output voltage is pretty faint and isn't enough to run a single LED. By the help our trusty "Joule Thief Circuit", the LEDs would glow even at low voltages.

Is It Really Powered By Water?
Well not really, the water serves as an electrolyte, a replacement for toxic chemicals used in regular batteries, which usually ends up in dumpsites. So why call it water powered? Of course no one would be interested in the title "Galvanic Flashlight" plus that's what easily pops up in people's minds. The Redox reaction takes place in this project.

Practical Uses:
1st.) If you got lost and stranded out in the woods, you can't rely on batteries, eventually they run out. A mini version would save stranded people in the woods. Just go to the nearest river and fill her up! Whala, you have light!
2nd.) School science experiment
3rd.) A fun and educational project for all ages!

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A Larger Scale Water Powered Project (a.k.a Galvanic Cell):

Step 1: Gathering Tools & Materials

Parts & Materials:
- PVC Pipe 4" Long (3/4"‎Ø)  [Local Hardware]
- PVC Coupling 3/4" to 1" [Local Hardware]
- Recycled 3xLED Torch  [Inventory = Free]
- Toroidal Core/ Bead  [Recycled From CFL Bulb]
- 2N3904 Gen. Purpose NPN Transistor [Radioshack] 
- 1K Ohm Resistor (1/4w) [Radioshack]
- Cooper & Zinc Strip  [Local Hobby Shop]
- Magnet Wire/ Copper Wire [Inventory/ Local Hardware]
- 4 Sheets Of Tissue Paper [Toilet/ Bathroom]
- 2x2" Sheet of Acetate [Bookstore/ Office Supplies]

Tools & Equipment:
- Leatherman MultiTool
- Soldering Iron
- Hot GlueGun
- Teflon Tape
- Super Glue

Step 2: Preparing the Power Cells

The power cell is your flashlight's main source of energy. Basically there are two strips of metal, one for the anode and one for the cathode. The "Copper Strip" will provide the positive energy while the "Zinc Strip" for the negative. 

Procedures: Assembling The Power Cell:
1st.) Roll tissue paper around your "Copper Strip" until you reach the 3rd sheet.
2nd.) After reaching the third sheet, roll the "Zinc Strip" until you reach your final sheet, which is the 5th sheet.
3rd.) Now tie some copper wire around the PowerCell, this prevents your tissue from tearing once it gets wet.
4th.) I recycled a pulley since it fits snugly on the PVC Coupling, puncture 2 slits for the metal strips to fit in.
5th.) Insert both metal strips through the pully's hole and seal/ waterproof it using epoxy/ superglue/ hotglue.

Step 3: Assembling the Joule Thief

What's A Joule Thief? 
A "joule thief" is a circuit that helps drive an LED light even though your power supply is running low. What can we do with it? We can use it to squeeze the life out of our drained batteries. Bottom-line, this circuit makes LEDs glow even at low voltages.

Let's get started! Hummm, you probably encountered a joule thief before. Lucky for you I have a more detailed guide about making a simple joule thief found here: Making A Simple Joule Thief (made easy)

If you already know how to build one, you can just follow the simple diagram from above. I needed to make my circuit more compact so I soldered my transistor below the LED's board while the toroidal core was glued above the LED's board.

Click Me! Visit my full tutorial on building a joule thief.

Step 4: Combining the PowerCell & Joule Thief

You probably came to a realization that the flashlight, uses to two separate projects, the PowerCell and the Joule Thief circuit, in order to work. 

For this step, solder the wires of the "PowerCell" to the "Joule Thief" then apply superglue around the coupling. Finally superglue the LED's reflector to your coupling.

Step 5: Preparing the Water Storage Cylinder

Get a 4" long PVC pipe then glue a small piece of acetate, this let's you see if the flashlight still has water. 

Step 6: Fill Her Up!

Just fill in tap water and you are ready to go!

Attention: Tap water won't last for more than 30 mins. They lack electrolytes. Saltwater will boost to the flashlight's glowing time but still it would only last for 2 hours. Vinegar & Gatorade works best, since they both contain electrolytes (lots of them). 

Adding a second cell triples the glow and lighting time!

Tested Liquids As Fuel:
- Tap Water = 0.5v - 0.6v (@400 mAh)
- Saltwater  = 0.6v - 1v    (@600 mAh)
- Vinegar     = 0.8v - 1.2v (@850 mAh)
- Gatorade   = 0.9v - 1.1v (@700 mAh)

Step 7: You're Done!

Let's light up the world, with free energy! Also, don't be shy to share your own version of the Water Powered Battery, just leave a comment & photo below.

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1 Person Made This Project!


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7 years ago on Introduction

Oh dude thanks for this, voted too! We have an investigatory project for chem class. A project like this would do great. How about: "Testing the feasibility of galvanic batteries" (a.k.a "Water Powered") for the title?


Reply 7 years ago on Introduction

That's a good title :)) Similar to our last year's IP title, about the feasibility of hydroponic planting.


5 years ago

Will urine be able to power the flashlight too? For example, if water is not available in a forest or something


Reply 1 year ago

You just mentioned a best way for survival in the wild. it should work, but bright as u think


Question 1 year ago on Step 7

If I made it like a coil, will it boost the voltage?

For Example, you've used less than 4 inches of Copper and Zinc Strips. If I used longer strips, will I get a better performance out of it?


Question 2 years ago on Step 7

Is it possible to add on/off switch?


Answer 1 year ago

Yes, but it would almost be a waste since the length/time of power for the light.


Question 2 years ago

From what thing did you get the pulley? Your answers would be very helpful!!!


2 years ago on Step 3

If you don't want to go through the work of constructing a joule theif circuit, a 5252f is a IC they use in solar lights that use a small 4 pin package and a inductor to do the same thing, you can get them fairly cheap on ebay.


6 years ago on Introduction

Very neat.

As an aside, this bugs me whenever I see it: "Whala" or "walla" etc. The word is "voila" - a common French word - and I also don't know why so many people think the word starts with "w" because the "v" IS pronounced - as in VWALLAH.


Reply 2 years ago

I learned the correct spelling, origin and usage of "voila" when a teacher graded a paper I had written which contained the word ”volla." I will always be thankful to my fifth grade teacher for his guidance.
(Note: Although this is a true story, I do feel bad about poking fun about an otherwise well written Instructable. Don't let us snarky English majors discourage you from sharing your scientific knowledge.)


Reply 3 years ago

Hurrah, someone else noticed.


Reply 5 years ago

Thank you! That was driving me crazy.


Reply 5 years ago

This is one of my favorites too.... It's usually 'viola' which doesn't make phonetic sense either. Happy to see other voila police out there cleaning up the world.