What’s more low-tech than a bicycle and the energy produced by the strength of the thighs and calves?
Of course, I’m talking about an electricity-generating bicycle!
In this article, we will present to you, step by step, the DIY realization of this bicycle generator.
Two objectives:
- that this bike is made from easily found objects,
- that this bike is capable of charging small electronic devices: mobile phones, computers, etc.
Let’s go!
Materials needed to make a generator bike
- A bike
- A bike rack
- A 24V DC electric motor (or scooter, like 44V 300W)
- A DC-DC battery charger (300W 20A type)
- A car battery, or something similar (example: 12V, 18A)
- A DC-AC inverter (400W type)
- Electric wires, gadgets and electric machines,
- Bicycle tools.,
- A multimeter!
STEP 1: The back support
To get started, you’ll need stands to hold your bike up and be able to pedal in place.
No need to spend money if it’s too expensive for you: it is possible to make them.
We, for example, bought a stand for the rear and made our own stand for the front.
Why did we prefer to buy the rear support? Quite simply because most of them are adjustable from right to left, which will allow you to easily align the chain, to increase engine performance.
STEP 2: The front support
As you can see in the photos below, we used cleats and wooden planks for the front to create a T, drilled at the top to slide in a threaded rod that will support the bike.
It is important to think about the height, in order to maintain a comfortable pedalling position.
The best thing is to get closer to the base height of the bike while ensuring stability.
Wooden front support 
Zoom on the threaded rod
STEP 3: The bike!
For the bike, obviously, no need to choose a new bike: An old bike without a wheel will do the job very well.
As long as the crank spins it’s good.
A saddle is better… too.
STEP 4: Choosing the engine
From there, it becomes more complex because you will have to decide between two types of engines.
Either you have a rear wheel and you can use it by friction to turn the motor.
Either you prefer to use the chain and the transmission of the bike directly.
You should know that using the chain is a complex option because you have to find the perfect gear to drive the engine to the right speed.
We, therefore, recommend that you use the friction solution, which is less effective but much simpler.
STEP 5a: Wheel option
Using this method is therefore the simplest: all you have to do is find a motor with a roller, which can make the connection between the motor and your wheel.
With a few aluminium plates, a hinge and a bit of common sense, it will be very easy for you to make adjustment support for your motor, in order to fine-tune the size of the contact surface between the wheel and the roller.
The difference in size between your wheel and the roller being significant, a speed between 20 and 30km/H will be enough to provide the correct speed to your engine.
Friction drive 
Adjustable engine block 
The pebble, makes the link
STEP 5b: The string option
The problem with this option is that you need a second chain, and you have to change the chainrings and the gearbox, to have a transmission with a huge gear ratio in order to be able to reach a fairly high voltage.
It is quite complex, especially if you are not comfortable with mechanics.
STEP 6: The charger
How does it work? To charge a battery needs a higher voltage than its output voltage.
On the other hand, swinging too much voltage on it can damage it and reduce its lifespan.
You will therefore have to choose a charger that corresponds to the limit of your battery, so as not to blow everything up and create a black hole.
Knowing that the motor voltage will be proportional to the pedalling speed, you will have to find your maximum charging current.
Well otherwise it’s very simple: just measure the output voltage of your motor with the multimeter, and connect the + output to the + input of your charger. And then – with the -.
You should know that the motor works in both directions so can also supply a reverse voltage.
Be careful not to overload the charger, because, with a chain system and a good gear ratio, it will be very easy to exceed 24V and burn out your charger.
An example with a 12V battery and an iPhone 5, which has a 1440 mAh battery: If you manage to get 2A out while pedalling, you will need 40 minutes to charge your mobile phone. And 20 minutes, with 4A.
STEP 7: Battery
Why a battery, when you can charge directly by pedalling? Quite simply for concern of surplus storage!
Charging a laptop can take hours of pedalling, so a power bank will save you pedalling time.
The choice will be important: a lead-acid battery is quite dangerous in the event of a fall or overturning.
We will therefore prefer a sealed battery, like those used for boats.
And rechargeable of course!
FYI, an 18A battery can charge 3 laptops.
For the connection, as for a car: first connect the + and then the -, for safety reasons.
Namely, the voltage will vary, in charge at rest, and in discharge. Respectively, 14V, 12.5V and 11V.
Be careful to check the technical data sheet of your battery so as not to exceed the maximum charging voltage. Here, 14.4V for our battery.
STEP 8: The Inverter
The inverter will convert the direct current from your battery into an alternating current, which is found in all wall outlets.
A very simple example: the cigarette lighter in your car, which is connected to the battery, allows you to charge your GPS or GSM.
When buying it, you should make sure that it provides enough Watts, in relation to what you want to charge: a telephone requires 5W… and a microwave 1500w.
The price will depend on that!
On the other hand, no need to focus on 120V: between 110 and 130, with few differences.
It is also necessary to take care to find an inverter which accepts a voltage of 12 and more since in charge, we have seen that the battery can go up to 14, or even more!
Also, be careful: this is a device that will heat up. So be careful not to suffocate it, but to leave it in a ventilated place.
You will need to connect the + battery to the + inverter, and then – to the -.
The bike-generator in action
To conclude this article, here are several videos that show the system running :
And There you go !
Obviously, we note that it is a low-tech techno which still requires some knowledge in mechanics and electronics.
Not sure if it’s within everyone’s reach, but it still gives you an idea of the feasibility of such a system.
