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Question about Led's Answered

Recently I took apart one of those dollar store led flashlight's. There is 5 led's in it . all the +  anode were connected to each other and all the - cathode were conected to each other and they were conected to 4 button cell batterries no resister or any thing else does that mean that each led runs on 6 volts and as long as I use a 6 volt dc battery they should work fine without a current limiting resistor and if I run them in series I could use 12 volt battery. the led's look white but they give off a blue light?

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sml156 (author)2009-12-31

Thank's guy's i dident know The LED's probably need about 3.2 - 3.4 Volts and that the button cell's were limiting the current and andygadget thanks for the caculator

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seandogue (author)2009-12-31

the batteries are probably run in series to develop 3V, to which the paralleled leds are attached.

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AndyGadget (author)2009-12-31

Using LEDs with button cells and no resistor is a 'quick and dirty' way to do it which usually works because the low voltage and internal resistance limit the current.
If you want to run from a higher voltage, you need a resistor in there to limit the current.  There's useful information and a calculator HERE.
And HERE'S an answer I gave a while ago to another question.

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andersonee (author)2009-12-30

NO! button cell batteries have a higher internal resistance that limits the current. If you connect the LED's to a different 6 volt source (like 4 AA's) you would burn up the LED's. The LED's probably need about 3.2 - 3.4 Volts.

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