Generating your own electricity by hand is a fun and educational project that teaches you basic physics principles. It also helps to protect the environment from other methods of energy generation that create harmful pollution.
Start with your DC motor. You’ll want to find one that has reasonably high voltage and amperage. I’ll describe the steps for a 12 volt, 1amp motor. Just make sure that you match the voltage of whatever motor you use to the voltage of the batter you use. That way your electric generator will be able to charge the battery.
Now, create a crank for the axle of your electric generator. Use any piece of material such as plastic, wood or metal, just so long as you can securely attach it to the shaft of the motor. While not required, by adding gears to your crank and axle, you can increase the number of turns the shaft makes every time you turn the crank. That will increase the electrical output of your generator.