# How to wire a blue LED light to 2 AA batteries?



## Mungoo (Mar 20, 2012)

[h=1][/h]I want to know if it's possible to wire a 2 AA battery pack to one blue LED light. The output of 2 AA alkaline batteries is 3v, but I don't know what LED and resistor to buy. Please don't tell me I would want to get a 4 AA battery pack, I need to be as cost efficient as possible.


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## A10K (Mar 20, 2012)

Do you have the data sheet for the blue LED? Many blue LED's run at a higher Vf than 3V, which means you will not be able to get it to light/run at full power using only two AA batteries, especially considering that the rated 1.5V, if you ever get it, will sag under load and drop with discharge. You would need to set up a boost circuit in order to be able to reliably use 2xAA's (or rechargeables, which have a lower voltage. If you're looking at cost efficiency you'll want to make that switch sooner rather than later). Here's a basic boost circuit. There are others, too: http://www.reuk.co.uk/DC-Voltage-Multiplier-Circuit-Plans.htm


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## FRITZHID (Mar 20, 2012)

well, if it's a simple 3.2v 5mm LED, 3v should be sufficient enough to power it to 80%, which should be enough for your application. a little more info on the project would help us inform you tho.


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## JohnR66 (Mar 20, 2012)

The voltage on new alkaline AAs are ~1.6 volts. Most Indium Gallium Nitride (bright white, blue and green) LEDs work fine connected direct. They stay bright for many hours and run for months at a dimmer level.

I hot glued a 2xAA holder with a green LED to the inside of my garage door and aimed it through the garage window so I could see that the door is down before going to bed without having to go outside to check. I change the AAs every six months or so.


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## MikeAusC (Mar 20, 2012)

Any Driver designed for White LEDs will work - they're just Blue LEDs with a phosphor layer.

Why use 2 AAs - there are plenty of 1xAA drivers.


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