ThreeAAAto18500LiIon

Replacing Flashlight 3 AAA Alkaline Battery Cartridge

with One Rechargeable 18500 Lithium Ion Battery

9LED3Cell.jpg

9 LED plastic flashlights using 3 AAA alkaline batteries in a round battery holder are inexpensive and reasonably tolerant of abuse.

Sadly, they use up alkaline batteries fast, which are more expensive than the flashlight. As the batteries wear out, voltage drops below 1.2V, the flashlight dims, and becomes unusable while there is some energy left in the batteries. Worse, old alkaline batteries fail and leak alkaline gunk that corrodes the innards of the flashlight.

Fortunately,