Want a DIY painfully bright rechargeable flashlight? Look no more, as here is one bad darkness kicker! I took a Nokia cellphone battery,combined it with a USB LiPo charger, a switch, and a few resistors, with a massive 700ma, 3.3v White LED.
USB LiPo Charger
BL-5C Nokia Battery
(4) 1.5 Ohm 1/2w Resistors
Optional 10w Resistor (would handle up to 5 LED’s)
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The ever handy LED Calculator suggested a 2w Resistor, so I put (4) 1/2w resistors in parallel. If you need more light, you can add another LED, with another 2w of resistors. Just parallel the first set. You could even have a high / low switch, that only brings the second set on in the high position.