Home & Garden Home Make a Water Powered Flashlight By Megan Treacy Megan Treacy Writer University of South Carolina Megan Treacy is a freelance writer from Austin, TX. A former editor at EcoGeek, she worked as a technology columnist for Treehugger from 2012 to 2018. Learn about our editorial process Updated December 3, 2013 ASCAS Share Twitter Pinterest Email Home DIY Pest Control Natural Cleaning Family Green Living Thrift & Minimalism Sustainable Eating Instructables user, and TreeHugger favorite, ASCAS has created another great clean energy project that is simple to make and super useful too. Here's what he had to say about the water-powered flashlight: The flashlight runs 30 minutes continuously with tap water and 2 hours with saltwater. Not bad for a single-celled prototype. This thing also works well with calculators, clocks, and 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. The output voltage is pretty faint and isn't enough to run a single LED. With the help of 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. 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 follow the river's trail (the river leads people) you'll have a 24/7 supply of light! 2nd.) School science experiment 3rd.) For Fun! 1 of 7 Materials credit: ASCAS 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 2 of 7 Preparing The Power Cells credit: ASCAS 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 pulley's hole and seal/ waterproof it using epoxy/ superglue/ hot glue. 3 of 7 Assembling the Joule Thief credit: ASCAS 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. 4 of 7 Combining The PowerCell Joule Thief credit: ASCAS You probably came to a realization that the flashlight uses two separate projects the: PowerCell Joule Thief, in order to work. For this step, solder the wires on your "PowerCell" going to the "Joule Thief" then apply superglue around the coupling. Finally jam the LED's reflector to your coupling and wait for 5 minutes for the glue to dry. 5 of 7 Preparing The Water Storage Cylinder credit: ASCAS Get a 4" long PVC pipe, but wait! Make sure there's a thread on the other side. I'l give you two choices: you can stuff in a cork on the non-threaded side and use a syringe to fill her up with water, or glue a small piece of acetate and use it as a water level indicator. 6 of 7 Fill Her Up! credit: ASCAS Just fill tap water in and you are ready to go! Attention! Tap water won't last for more than 30 minutes due to lack of electrolytes. Saltwater will give a boost to the flashlight's glowing time but still it would only last for 2 hours. Vinegar & Gatorade works best, since both of them contain a lot of electrolytes, glowing time would last for 5-10 hours! Tested Liquids As Fuel: - Tap Water = 0.5v - 0.9v (@400 mAh) - Saltwater = 0.7v - 1v (@600 mAh) - Vinegar = 0.9v - 1.2v (@850 mAh) - Gatorade = 0.9v - 1.3v (@700 mAh) 7 of 7 You're Done! credit: ASCAS Let's light up the world with renewable energy!