# Choosing leds for batteries power

Can I use 3V (2*AA or 2*C batteries in series) as power for 10/20 leds connected in parallel?

LED specs:
Diameter: 3mm / 0.1"
Emitting color: Red/Green/Blue/White/Yellow
Material: GaP
Forward voltage: 1.8-3.4V
Forward current: 20mA
Backward voltage: 5V
Wavelength: 460-630nm
Frequency characteristic: Low frequency

I will connect only 1 collor lets say 20 red or 20 green leds... need them to work at 70-100% of intensity... the batteries model and number is not a limit I am just searching now...and yes I can make a connection of 3*C batteries in series

If the LEDs are to be directly powered by the batteries, the blue, white, and possibly the green LEDs (depending on which type of green LED it is) will not work at all on 3 Volts: They require a forward voltage of 3+ Volts, 3.4 Volts as specified in the question.

Also, once the voltage starts dropping due to depletion, even the marginally lit ones (e.g. the green, may be the orange) will no longer work.

Therefore ideally only red LEDs should be used: Red LEDs typically have the lowest operating voltage amongst visible colors. Alternatively, as noted, 3 cells would be needed in series.

• Strange this post is 'protected' as it says below, I'm learning about basic electronics and i found your answer really useful :) Question tho, what is a forward voltage and what is a voltage drop, and do all components have a voltage drop across them? – Agent Zebra Aug 27 '15 at 3:34