photocell to turn LED on questions

team_nightstalker said:

ok here is my main question of concern. at a run time of 8 hours.... how long should the batterys keep up to this LED?

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Simply visit a battery manufacturer's website and look at their datasheets.
www.energizer.com shows that AAA alkaline cells can power an LED at an average of 25mA for about 48 hours. A 9V alkaline battery can power an LED at an average of 25mA for about 24 hours. The voltage continues to drop so the LED dims.
Ni-MH rechargable cells are also shown.

<b>Hero999,</b>
Thank you for the assistance. I was only trying to give Team_NightStalker some help/options. I knew the 3V circuit was a stretch and was hoping for the aid of
others to jump in and help.