http://www.outdoorlanternsonsale.com/white-leds/
How long can three white LEDS run off AA batteries?
Hi. I'm doing a POS design and need to incorporate 3 white LEDs. The thing is, they'd like it to run off of batteries. What would be a good solution battery-wise if I needed the LEDS to run for maybe 3 months?
Anyone?
Select the LEDs, look up the forward current, multiply by three months and size the batteries to suit.
example (other components required)
a 3mm 1.5mc white led has typical forward current of 20ma at say 3V
(pair of batteries) means each battery gives 30mW
Duracell graph shows this will last 100 hours.
You need many many batteries to last 3 months!
You could:
1) reduce the current and the light output to extend the life
2) have a timer to turn off at night/ unoccupied
3) flash the lights, may be more attention getting and power saving.
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