Portable 3.6V Water Powered Generator

Hello, and welcome to this Instructable on a water-powered battery!

Inspired by the power banks charged by solar panels, I wanted to see if I could make a similar build out of a different renewable energy - water. The goal of this project was to create a portable battery powered by the motion of water being shaken in a bottle.

My idea was to create something that could be attached to existing water bottles to provide an easy, portable way to charge your phone on hikes, or while camping, without needing to pack anything extra. Its small size allows it to be carried in the side pouch of a backpack, and it was even designed to allow the water bottle base to retain its original purpose - you can drink out of the generator!

Let's jump in!

1. Water Bottle
2. 22mm Ball Bearing
3. ~15 cm of a 5.5mm Wooden Dowel
4. 3D Printer w/ ~ 100g of Filament (I used PLA)
5. Hot Glue
6. Vinyl Tape
7. Hand-Crank Generator OR Separate Circuit Components (USB Charging Circuit, Rechargeable Batteries, Motor, Diode)
8. I used this generator for my build
9. Optional - Soldering Iron

Material Costs:

I sourced most of the materials in this project from items I already had around the house, which helped save money. For example, the steel ball bearing was popped out of a fidget spinner, and the wooden axle I used was a chopstick. Ultimately, this reduced the total cost of this build for me to just the price of the hand crank, or ~10$. If you end up needing to buy some of these materials, it may cost a bit more, but total price should be below 20$.

Note on Circuit Components:

I chose to buy the generator as it was the cheapest way to source all of the electrical components I needed in the project. Thus, most of the circuit work was pre-built for me. However, if you want to learn more about creating circuits with the build, you can build your own with individual components. This might also require adjusting some of the 3D printed components, as my designs were created to custom-fit parts from the generator I bought.

Note on Files:

Below are all of the print files needed for the build. They are linked again under the steps they are needed for, along with their respective CAD models, in case you want to make edits. Every file only needs to be printed once, with the exception of the turbine, which can be printed anywhere from 1-3 times (I used 2).

Drill a hole through the bottom, center of the water bottle. (See Image 1)

• I used a 15/64" drill bit, but sizes may vary by the diameter of the axle you want to use. Feel free to sand down the axle, or expand the hole until you have a smooth, fairly loose-fitting joint.
• Don't worry about waterproofing this joint yet, the hole should simply be big enough to allow your axle (dowel) to rotate freely when inside.

Tip: Often, the center of the bottle has a hard plastic lump, which can be hard to catch with the drill bit. I had some trouble with this step and learned that you can drive a nail into the place you want to drill to create a "pilot divot/hole" that will make it easier to drill with a large bit.

Attach the turbines to one end of your axle. (See Image 1)

Wrap the axle in electrical tape to create a friction fit for the turbines. Then, seal it with hot glue. There should be ~1/4" of the axle sticking out from the turbines.

• From my testing, I found two turbines worked best to produce the max RPM for my bottle size; larger bottles might benefit from more, and even larger turbines, which can be tweaked in the CAD files.

Put the axle through the hole in the water bottle until the turbines sit roughly halfway inside the bottle. There should be ~1" of the axle sticking out from the bottom of the bottle (See Image 2) - any excess can be trimmed with a pair of pliers.

Insert the ball bearing into the bearing housing and secure with a small ring of hot glue. (See Image 1)

Wrap the end of the centering ring with vinyl tape, and slide into the middle of the bearing. (See Image 1)

• This fit should be tight and waterproof - seal with hot glue.

Note: When using hot glue around the bearing, be extra careful that none of it interferes with the rotation! Speaking from experience, it's really annoying to take apart and clean.

Attach the bearing housing to the bottom of the bottle with hot glue, centered on the axle. (See Image 2)

• If the fit is too loose, wrap the axle with vinyl tape until thick enough to create a seal.
• The closer this connection is to a perfect 90 degrees, the more efficient the system will be.
• After this step, the turbine should be able to spin freely within the bottle.

Tip: Spray the bearing with a coating of WD40 to help with lubrication and water resistance.

Screw on the outer bearing housing.(See Image 3)

• With the exception of the joint between the axle and outer bearing housing, every connection in this step should be waterproof.

Wrap the axle in vinyl tape until you create a waterproof inner seal between the water plug and axle. (See Image 2)

• ~2 wraps created a good seal on my model
• Make sure the connection is tight enough to keep water in, but not so sticky that the plug can't be moved at all. The plug will have to be disengaged later to allow the axle to spin.

Wrap the outside of the water plug with vinyl tape until you create a waterproof seal between the plug and the outer bearing housing. (See Image 3)

• ~5 wraps created a good seal for me
• Like the inner seal, the outer seal should also be waterproof, but able to be moved.

When the plug is engaged, (pushed into the bearing housing), the bottle should now be waterproof. The plug should also be able to slide along the axle so it can be engaged to protect the circuit, but disengaged to allow the axle to spin without too much resistance.

• Image 1 - Plug Disengaged
• Image 4 - Plug Engaged (With water in bottle)

Note: Waterproofing each joint was an extremely important, but also tedious process, involving a lot of trial-and-error for me. Especially in this step, I've tried to make it easier by sharing the numbers it took for me to achieve a good seal, but it may take a while. Make sure to double check everything before moving on to circuitry by filling the bottle with water and shaking! (You probably want to do this in a bathtub)

Note: As stated previously, most of the parts in the circuitry steps are custom made to fit with components from the hand-crank generator. You can make your own circuit (This seems like a good set of instructions), but the 3D models will need editing.

If you have the generator, start by taking it apart, saving the motor, battery, board, and optionally, the LEDs.

Once you have the electrical components needed, slip the motor mount over the outer bearing housing.(See Image 4)

Next, If you have the motor I used, you'll need to bend the motor's mounting plate for it to fit within the bottle's diameter. At the seam, bend the overhang towards the motor's gear. (See Image 2)

• The closer this angle is to 90 degrees, the easier it will be to mount.
• Pliers make the job a lot easier, but the metal is also thin enough to be bent with your hands.

Next, join the motor to the axle. With the motor I used, simply slip the motor adaptor over the motor's gear on one side, and the axle on the other, securing with hot glue. (See Image 3 & 1)

• Keep in mind that the water plug from last step will rest on the lip of the adaptor when it's disengaged

Screw the motor into the mount and use hot glue to secure the mount to the outer bearing housing.

• Both screws will come from the hand-crank generator

After this step, the motor should now spin freely, connected to the turbine.

Note: Mounting the motor at the right angle is extremely important to the efficiency of the system. This might take a few tries, but the lower the friction on the axle, the better.

Slide the bottle cover over this assembly, attaching to the bottom of the bottle and secure with hot glue. (See Image 5)

Note: If you're careful enough taking out electronics from the hand-crank, you can skip the soldering steps - I was not.

Start by soldering the battery cell to the board (See Image 2)

• The board is pretty self-explanatory; red to B+, black to B -.

Prepare the circuit housing by snapping in the LED housing on the wall, and the button on the bottom. (See Image 3)

Slide the circuit board into the housing.

• This is easiest if you start by putting the LEDs into their place, then pushing the USB ports down, lining them up with their respective positions.
• The remaining screw and button holes should now be aligned.
• Glue down the battery cell in the small opening opposite to the LEDs.

Screw the board down with 4 screws from the hand-crank. (See Image 4)

Finally, connect the motor to the board. (See Image 1)

• Soldering is slightly harder as wires aren't marked, but the middle wire (which is crimped) corresponds to the middle terminal, and when the wires are laid flat and uncrossed, right goes right and left goes left.

All electrical functions should now work:

• The button on the bottom controls the LEDs
• The Green LED on the bottom indicates battery charge status
• Both USB ports can now charge

The bottle should now be finished!

Engage the plug to fill the bottle with water, turn the bottle upside-down, and disengage the plug. Screw the circuit housing onto the bottle cover and shake!

Note: When water is in the bottle and the plug is disengaged, remember to always keep the circuit housing on top to prevent water damage. Make sure the plug is engaged if the bottle is right-side-up.

It seems that the best way to power these turbines is to shake in a way that creates a "vortex" in the bottle. While simply shaking back-and-forth does work, the movement of the water ends up spinning the turbine in two different directions, cancelling much of the force put in. The vortex does a much better job of spinning the turbine in a constant direction.

Thank you for reading all the way through!

This was my first ever Instructable, and I had a lot of fun with it. Start to finish, it took me just under 3 weeks. For me, the research, prototyping, and fabrication stages in the project were a great way to learn about custom part design in CAD, the basics of fluid mechanics, circuit construction, and fabrication techniques, especially with the 3D printer.

I'm especially excited that the build turned out as functional as it did.

Optional Extra:

An optional bracket I designed to hold your phone while charging on the bottle linked to this step: (Designed for iPhone 14 Mini)

Future Improvements:

While building, I had some thoughts on improvements to the design that I wanted to share somewhere in the Instructable;

First, power output (RPM) can be increased in multiple ways:

The most obvious solution for me was just to increase the size of the bottle; more water obviously means more force spinning the turbines. I think this comes down to the user's preference, as the bigger the bottle, the less portable it will be. In my build, I designed around a bottle given to me for free, so I wasn't as picky with size.

Next, a larger stack of turbines could also help increase the surface in contact with the moving water, spinning the axle with more torque. However, there would definitely need to be further testing to find the balance between turbine size, and overall water capacity of the bottle.

As for general improvements to the design, I had two;

I think replacing the steel bearing with a ceramic one would help the water resistance, and therfore, longevity to the design.

Finally, the waterproof seal could be replaced with one that worked while rotating. The existing design has too much friction to allow the axle to rotate while engaged, which is why the bottle must be upside-down while shaken. I think a seal similar to those used on boat propellers could vastly improve the convenience of the design.

With many of these improvements, a major constraint for me was cost. I tried to make this version as cheaply as possible, which was a big reason I didn't include these elements in the presented version. However, if budget isn't as big of a concern, adding them could make for a much more polished build.

Thank You!