Induction Powered Cell Phone Charger Help?

Discussion in 'The Projects Forum' started by cheezycheeze, May 16, 2013.

  1. cheezycheeze

    Thread Starter New Member

    May 16, 2013
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    Hey Everyone!
    I am plan on creating an induction powered cell phone charger using the magnet coil system from a shake flashlight, a rectifier, NiMH batteries, and an double AA powered emergency USB cell phone charger. Now how exactly do I achieve this?

    What I am thinking is if I take the two ac wires to the rectifier. Then take two DC wires form the rectifier and make them touch the batteries? Then when the USB charger is turned on, the batteries discharge and power the cell phone? Is it as simple as that?

    Any Help is greatly appreciated!
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You need to make sure the "Faraday Torch" gives out at least 3-4 volts to charge the nicads.
     
  3. cheezycheeze

    Thread Starter New Member

    May 16, 2013
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    But at the end, in order to charge the batteries, all I need to do is bring them into contact with a 3-4v power source correct?
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    I don't get it. What is charging what?
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    If i get this right , i think he wants to use the torch to charge the nicads, and then use the nicads to charge his phone.:confused:
     
  6. cheezycheeze

    Thread Starter New Member

    May 16, 2013
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    Yeah. Basically, the shake flashlight mechanism charges -> NiMh batteries which then charge -> any USB device through the AA emergency USB charger.

    The problem is, I have no idea how to get this going.
     
    Last edited by a moderator: May 17, 2013
  7. Dodgydave

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    Jun 22, 2012
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  8. cheezycheeze

    Thread Starter New Member

    May 16, 2013
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    Thanks everyone! Today I was able to power up an led woohooo directly from the magnet-coil system through a diode bridge rectifier and capacitor. I took some readings, an dwas able to generate 2.2 volts and a sad current of 1 to 2 mAH. Now, is there any way to amplify this current to around miliamps? I have two NiMH batteries that have a capcitance of 2000 mAH and to charge them i need atleast 200 mAH.
     
  9. piratepaul

    Member

    May 20, 2013
    35
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    What about charging phone batts from the rectifier with out all the bits inbetween.
    I have a phone batt with 3 terminals... why?...I run alot of 18v drills, saws etc on 24vdc no black smoke yet!...I could do with charging the phone.
    Why do phones have silly batts?
     
  10. cheezycheeze

    Thread Starter New Member

    May 16, 2013
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    Cause the electricity being generated isn't that steady. As in the current jumps between 1 and 4 miliamps and the voltage spikes between 1-3 volts. Wouldn't that be unsafe for the cellphone?
     
  11. cheezycheeze

    Thread Starter New Member

    May 16, 2013
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    And a side question, does current add up? As in WHAT IF, hypothetically, I had an array of these magnet coil systems (50 or so) in like a rectangular box within thier own housing and when i shook the box, would I get 50 miliamps of current?
     
  12. MrChips

    Moderator

    Oct 2, 2009
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    cheezy, you're new to this game so you gotta learn the rules right.

    The units of current are μA, mA or A, not mAH.

    Batteries have capacity not capacitance.

    You can charge the battery with any current as long as it is not too high. A low current just means it will take a lot longer to get any charge into the battery. We used to charge AA NiCds at 40mA. Charging a 2000mAh battery at 200mA will take about 10 hours.

    If you want the shaker generator to produce more current you can add more turns to the coil, use a stronger magnet or shake the charger a hell of a lot faster.
     
  13. cheezycheeze

    Thread Starter New Member

    May 16, 2013
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    Thank you for correcting me! That makes definite sense however, I still am curious: Can current be combined? Let's I have two magnet-coil shake systems. If I hook them up to the same rectifier, will there be more current as compared to having only one shake charger?
     
  14. aws505

    Member

    Mar 11, 2013
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    It would be the exact same as having one coil with twice the number of turns.
     
  15. aws505

    Member

    Mar 11, 2013
    59
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    I'm so wrong!! A coil with twice the number of turns would give you twice the voltage, but the same current (since the series resistance of your source has now gone up by a factor of two). Two coils in parallel would give you the same voltage, but twice the current (since the effective series resistance of your source will have dropped by a factor of two). My bad :(
     
  16. piratepaul

    Member

    May 20, 2013
    35
    2
    What I was thinking is take the batt out and charge it.

    I charge 4 AA nicads from a 2.5 watt 6v solar panel, the panel hits just over 10v open circuit in good sun, it charges the nicads like zip...

    It seems to me elbow grease is the flaw in your system, perhaps 2 solanoids and a 50Hz osscilator to shake the torch might give a better output, but then the power supply to the sol or sols would be the flaw...

    May be a dynamo torch would give better results.

    I dont mean to knock your shaker ... you must be able to get more than a few mA... what about putting the torch on a washing machine ... may be take the concrete block out of the washing machine for extra shake.

    Why do laptops have silly batts for that mater?
     
  17. cheezycheeze

    Thread Starter New Member

    May 16, 2013
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    Alright everyone! Good news here, today we replaced the diodes from 3.3 volts to 50 volt 1 amp diodes, and now we max out at a direct current of about 20 miliamps! Hooray! Now the question is, what is the minimal number of miliamps needs for a phone to just display "charging"? As of now, our magnet-coil system charges a 2 NiMH batteries which are then placed in to emergency AA cellphone charger to charge a phone. The question is, can we completely remove the middle man (aka the NiMH batteries and the AA emegerncy cell phone charger) and hook the power wirse of a usb cable from the DC output to the phone?
     
  18. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    Unfortunately, you would need to increase the speed of the moving magnet to increase the current. You have undoubtedly have found out it takes a lot of energy to shake the magnet for several minutes.

    BTW, you measure current in mA, not mAH. The capacity of the battery is in mAH since 2000 mAH can provide 200 mA over 10 hours.
     
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