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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, an 18500 rechargeable lithium-ion battery is the same length as the battery holder, holds twice as much energy, does not drop voltage nearly as much, and can be charged in an external charger and reused many times. |
