Can You Charge Batteries with a Magnet and Copper Coil?

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    Battery Charge
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Discussion Overview

The discussion revolves around the feasibility of charging batteries using electromagnetic induction, specifically through the motion of a magnet within a copper coil. Participants explore the principles of induced electromotive force (emf) and the necessary conditions for charging batteries, including voltage requirements and circuit design considerations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes an experiment involving a magnet passing through a copper coil to induce emf and expresses interest in using this setup to charge batteries.
  • Another participant suggests the need for a diode to prevent current from flowing back into the coil, which could drain the battery.
  • A different participant emphasizes the importance of producing sufficient voltage to exceed the battery voltage, including the voltage drop across the diode, to allow charging.
  • There is a question about whether a voltage lower than the battery's voltage could still result in charging, with a suggestion that it might just take longer.
  • One participant asserts that no charge will flow unless the supply voltage is higher than the battery voltage, proposing alternative charging methods if the voltage is insufficient.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of exceeding the battery voltage for charging to occur, but there are differing views on the implications of operating below that voltage and the efficiency of the proposed setup.

Contextual Notes

Participants note that the efficiency of the setup may be low compared to other methods, such as a rotary generator, and that the design may require significant adjustments, such as increasing the number of turns in the coil.

Who May Find This Useful

This discussion may be useful for individuals interested in experimental physics, electrical engineering, and renewable energy applications, particularly those exploring DIY energy generation methods.

tmak
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Hello,

New here, sorry if this in the wrong thread.

I just finished a college general physics 2 course and in it we had an experiment where we passed a magnet through a coil of copper and a computer read what the induced emf was. This reminded me of a flashlight I have which uses the motion of a magnet going back and fourth to recharge two round 1.5 volts batteries, connected in series.

So, I created a similar setup using a coil of copper wrapped around a pvc pipe. I use a strong cylindrical magnet to go through this. It is attached to a led which lights sporadically as I shake the pvc pipe. I read I can attach a capacitor to the circuit to smooth out the current. And to use diodes to make the current DC.

Instead of light an LED I want to charge 2 1.5v rechargeable batteries I have in series. I think though that if I attach the two batteries to my coil of wire the current from the battery will create a magnet out of the coil and drain the battery, no? How would I be able to charge the batteries using the emf induced by the magnet going back and fourth through a coil of copper magnet wire?

Thanks!
 
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tmak said:
... I think though that if I attach the two batteries to my coil of wire the current from the battery will create a magnet out of the coil and drain the battery, no? wire?

Thanks!

Yes, it would. You need a diode to keep the current from flowing back through the charger.
 
You also need to be producing enough volts with your system (for a reasonable proportion of the time of each cycle of movement) to exceed the voltage of the battery (plus the 0.6 to 0.7V drop across the diode) so that current will actually flow to charge the battery. If you have a DVM, you can see what you get with an initial coil size and then scale it up to give you the volts you need (the Volts out is roughly proportional to the number of turns on the coil). You will need a lot of turns for this as it is not a very efficient setup, compared with a rotary generator.
 
Is it absolutely necessary to have 3+ voltage going to the 3v battery to have it charge? Or will the charge just take longer if the voltage from the system is less than 3v?
 
No charge will flow into the battery unless the supply voltage is higher than the battery voltage. You could always charge the batteries separately or in parallel if you can only get, say, 2.5V.
This sort of exercise is basically suck it and see.
 
Thanks sophiecentaur and phinds for the responses. I'll read up more on how batteries work. I think I have enough information now to continue with my experiments though. Eventually I do plan on creating a rotary generator, then a wind turbine which uses that.
 

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