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Thread: Led torch getting hot

  1. #1
    Unenlightened
    Join Date
    May 2020
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    1

    Default Led torch getting hot

    I recently purchased a Bluetooth speaker/torch/powerbank. I decided to pull it apart (as you do) and removed the led, battery and power switch. I did so because the led is white super bright and is approx the size of an Australian 10c piece. I had an old torch body lying around so decided to put the led, battery and switch into the old torch body exactly as it was when it was in the Bluetooth speaker. My problem now is that no matter what I try the negative solder joint on the actual led keeps heating up to the point where it simply melts the solder and separates completely from the led. Why does the negative joint get so hot, one would think that it would be the positive joint if any that would heat up but not in my case it definately is the negative joint. The battery is an 8000 mAh, 3.7v li-ion battery. Is there any way to stop this and why is it only happening now and not when it was still in the speaker.

  2. #2

    Default Re: Led torch getting hot

    Most likely the speaker cabinet had metal in it that was in contact with the LED some how to pull heat away from it. If this is the case you may need to add some metal (preferably aluminum or copper) mass to pull heat away from the LED. You could also try putting a resistor in series to reduce the power output and heat the LED needs to be removed from it.
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  3. #3

    Default Re: Led torch getting hot

    Quote Originally Posted by minjjjr View Post
    I recently purchased a Bluetooth speaker/torch/powerbank. I decided to pull it apart (as you do) and removed the led, battery and power switch. I did so because the led is white super bright and is approx the size of an Australian 10c piece. I had an old torch body lying around so decided to put the led, battery and switch into the old torch body exactly as it was when it was in the Bluetooth speaker. My problem now is that no matter what I try the negative solder joint on the actual led keeps heating up to the point where it simply melts the solder and separates completely from the led. Why does the negative joint get so hot, one would think that it would be the positive joint if any that would heat up but not in my case it definately is the negative joint. The battery is an 8000 mAh, 3.7v li-ion battery. Is there any way to stop this and why is it only happening now and not when it was still in the speaker.
    Okay. Electrons, the little particles that make electricity, are in abundance on the negative terminal of a battery. This is why it's labeled the negative terminal or contact. They flow from negative (cathode) to the positive side (anode). The circuitry in the speaker/powerbank was likely controlling just how many electrons were flowing to the little LED and thus keeping it from melting. As Lynx said it was probably also in contact with something that was a good heat sink, pulling the extra heat away from the LED and soldered connections.

    If you thought that little thing was bright you should see some REAL flashlights.

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