Modification  to make a  long burning LED flashlight

Parts list: 

Cheap LED key-chain flashlight that runs on 2 CR2016 batteries.
(One with an on/off switch is best but momentary will work also.)

CR2032 watch battery
5mm 6000+mcd 3.5v ultra bright LED

Instructions:

Take apart the flashlight case. Depending on type it may use a screw or snap-catch.

Replace the 2 batteries with the one CR2032 watch battery. 

The 2 CR2016 batteries together over drive the LED, in both current and voltage, in order 

to achieve its high brightness and if left powered on will burn itself out.

The single CR2032 provides 180mAh. That is twice the capacity of the two CR2016 in the same amount of space.

The new battery will be slightly under-driving the LED and giving a dim output. 

Thats where the new ultra bright LED comes in, and when sold in a red color it is quite cheap. 

Replace the old LED with the new red ultra bright LED . When inserting the new LED 

you may need to trim and bend it's leads to fit. Using the old LED as a guide can be helpful.

Finish reassembling your new flashlight keeping in mind the battery's polarity.
The larger capacity battery will give you a much longer run time with no danger of ever burning out your LED. 

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