Battery Life w/ 1 LED

oldmil · Dec 9, 2008

Hello all. Newbie here.

Can anyone tell me how long a 9v battery will power a single 5mm white LED (3.4v, 20 mA) with approx 330 ohm 1/4 watt resistor? I'm thinking of making a nightlite but figure it would be a waste of time if it won't last more than a few nights.

Thanks for your help.

Oldmil

Marduke · Dec 9, 2008

Here ya go
http://tutorials.boilingpondscemetery.com/LEDLighting/LEDCalculators.aspx

hopkins · Dec 9, 2008

welcome Oldmil - here is a chart that may give you an idea of the life.
They sell 3 or 4 cell holders for AA or aaa batteries at RadioShack (or similiar stores) Your finished light with one of these would be about the same shape as a 9volt led light but allow you to use rechargeable batteries.

TigerhawkT3 · Dec 10, 2008

Probably 10-20h.

Light Sabre · Dec 10, 2008

The best way that I know of for a 9V night light is to buy a PAL Safe Light. PAL Super Bright Safe Light PAL Super Bright Safe Light [Super Bright Safe Light] - $14.00 : GlowBug.com Lasts a year or 2 on one 9V battery using the "Find in the Darkness" mode. I have several of these.

hopkins · Dec 10, 2008

I've noticed recently that dark adapted eyes you can navigate a bedroom by the light of a single led driven by only 1mA . So if you select a resistor that
limits the current to your led to 1mA the light could last over 60 8hr nights
for one 500mAh battery

swj0001 · Dec 10, 2008

I made just what you're talking about out of 2 white 5mm led's in series with a 100 ohm resistor. It draws about 20mA from a fresh 9 volt battery. Your average 9 volt alkaline battery has a capacity of about 500 mAh, so I figure I can get about 25 hours out of one.

I learned how to make one off of a topic in here.

LED Flashlights. · Dec 10, 2008

I don't know how long the battery will last, but I will bet you the battery will leak before it goes bad.

Battery Life w/ 1 LED

oldmil

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