can i use one battery to power two leds?

I'm new to this whole led stuff and I want to make a flashlight using a set-up similar to this except using a D battery, and I would like to know if it's possible for that one battery to power 2 leds.

Picture of can i use one battery to power two leds?
framistan7 years ago
Most LED's require a resistor in series with the LED to limit the amperage to about  .010 amps (ten milliamps).  Each led should have its OWN series resistor.  Dont try to use ONE resistor to power several leds, it wont work too good that way.  (some led's will not be as bright as they should.  )  Use Ohms Law to calculate what resistor size you need.  Just use battery voltage (4.5 volts for your example)  divided by .010 amps equals resistance in OHMS.... equals 450 ohms. anything from 400 to 600 would light the led.  Dont connect leds BACKWARDS to the power . that is DEATH to an led. 
seandogue7 years ago
yes.<br /><br />If you can power one, then you have the voltage source necessary to drive the led, so you can power two (in parallel), but your runtime is reduced by the doubled load. You can add three, four, or even more... this assumes we're not talking about high-power leds, since raw current draw becomes more of an issue at large loading so may rquire mutliple batteries in parallel to successuflly oeprate multiple high-power leds in parallel<br /><br />Flashlight implies a white led, so you'll need 2 D cells in series to drive it without any additional circuitry. More complex circuit required for ideal Vf/If..<br />
It depends on how many volts the LEDs take to light them up.
You could also wire them in parrallel so if you could light up one you could also light up another