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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?




8 years ago

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

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

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.

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.