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Charge a battery with electromagnetic induction

Discussion in 'Power Electronics' started by michael tanzer, Aug 12, 2015.

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  1. michael tanzer

    michael tanzer

    Aug 12, 2015
    Hi everyone this is my first post, so be kind.
    My project should be really simple indeed: I would like to build a device that can charge a rechargable AAA battery using inductive energy.
    Regarding the inductive energy I already built a very-simple device made of one copper-made spiral and a powerful magnet (rare earth).
    Now the question is: how can I transform the alternate energy from the inductive device to charge the battery? I really don't care if the process is very long (the charging process i mean.
    Sorry for bad english. And good afternoon (3 AM now)
    Thank you everyone
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Basically you can place a diode in series with the coil, and connect it up to the battery in such a way as not to further discharge it.

    Then move the magnet back and forth through the centre of the coil.

    After some weeks, the battery may be a little more charged than it was when you started.
  3. michael tanzer

    michael tanzer

    Aug 12, 2015
    Thank you steve,
    I have got two questions for you:
    1. how much does 1h of back and forth charge one AAA battery? (stupid question?)
    2. can you explain the method better? I am not practical about this
  4. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    This is an open forum, so others here may have a few questions for you, too. I know I have several.
    What is inductive energy? Why do you think inductive energy is appropriate for recharging a AAA battery, as compared to, for example, electricity?
    What does your "very-simple device" actually DO? What is the purpose of the "powerful magnet (rare earth)."
    What "alternate energy" do you expect to obtain from the "inductive device?" Do you expect your "inductive device" to produce electricity? How much "alternate energy" is required to recharge a AAA battery?

    Many years ago, when men knew almost nothing about electricity, Michael Faraday discovered the principle of electromagnetic induction. He discovered, more or less by accident according to some historians, that if he moved a permanent magnet through a coil of wire, a small voltage would be generated between the ends of the wire while the magnet was moving. The ends of the coil of wire could be connected to an external circuit to cause a current to flow, thus representing the production of electrical power, P = V x I, where V is the voltage produced at the ends of the coil of wire (measured in volts) and I is the current produced in the external circuit (measured in amperes), and their product, P, is power (measured in watts).

    Faraday's external circuit was a galvanometer, basically a small magnetic compass with a horizontal needle, free to rotate on a pivot, and several hundred turns of wire wrapped in a coil over the needle. In use, the compass was aligned with the Earth's magnetic field such that the plane of the coil of wire was perpendicular to the needle. Passing a current through the coil created a small electromagnetic field that interacted with the magnetized compass needle to create a torque on the needle. The stronger the current, the more torque produced and the further the needle would deflect from its initial north-south orientation. This crude instrument is quite easy to make and can be made very sensitive by winding a lot of turns of fine wire around the compass case. One drawback to using it is the wire tends to cover up the compass needle making its deflection difficult to observe.

    The phenomenon described above was later called the Law of Electromagnetic Induction. It is the basis for every electrical generator that produces electricity by rotating a magnetic field through one or more coils of insulated magnet wire. The voltage produced by such a device is predictable and is the basis for engineering design. The voltage is proportional to the product of the strength of the magnetic field, how fast the magnetic field is changing, and the inductance of the coil.

    A novel, and perhaps even practical, use of the principle of magnetic induction was the commercial sale of a "flashlight" consisting of a coil of wire wound inside a plastic tube, a small rechargeable battery, a small light bulb or light-emitting diode, and a small but powerful rare-earth magnet that slide freely inside the coil when the plastic tube was shaken back and forth (or up and down). Shaking the tube to move the rare-earth magnet back and forth through the coil of wire would cause the light bulb (generally a "grain of wheat" bulb) or the LED to illuminate. Continued vigorous shaking would "charge" the rechargeable battery, much as sunlight recharges the battery in solar path-lighting. To keep cost to a minimum, there was no on/off switch.

    The above paragraph describes a method of generating electricity that is pretty simple, given that you already have the technology to produce powerful rare-earth magnets, refine copper ore to copper ingots and draw those ingots down to fine copper wires, a method to insulate the copper wire (Faraday used a silk or cotton cloth-wrapping but this was (much) later changed to a flexible enamel coating), a way to produce small light bulbs or light-emitting diodes, and a clear plastic tube in which to package everything. I suppose you could also ream out a wooden stick to use instead of a plastic tube.

    So, my final questions for you: just what are you bringing to this party, other than your imagination? What study and research have you done? This is not a teaching forum, per se. We help those who help themselves by engaging in a dialog of back and forth communication, hopefully clearing up any misunderstandings.
    Last edited: May 1, 2019
    GHamblin and Bluejets like this.
  5. Bluejets


    Oct 5, 2014
    This would be a great quote for many queries in here. :)
    bushtech likes this.
  6. Martaine2005


    May 12, 2015
    I absolutely agree with bluejets. Would have been even better four years ago!
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