Free Rechargeable Flashlight From LEDs and Lithium Battery




About: I am an engineer focused on recycled batteries, electric vehicles and renewable energy. I am always working on engineering projects I can’t stop.

Update: for my first test the flashlight laster 24 hours and 7 minutes before it needed a charge.

Building a long lasting, rechargeable and powerful flashlight is easy and cheap. I only used the following.

An effervescent table bottle
6 LEDs taken from broken christmas lights
1 18650 used laptop lithium ion battery
A switch
22 gauge wires

Step 1: Building It

Cut a small hole for the switch. Run wires through the hopes to connect the battery, switch and LEDs together. I used an electrical crimp connector to hold all negatives of the 6 LEDs together. I then soldered 2 sets of 3 positive LED wires together. I then installed the LEDs in the bottle lid. I soldered everything together.

Step 2: Trying It Out

The flash like works really well. I wrapped the battery in cloth so it would fit snuggly and would not move in the bottle.

The light is very bright. I installed no focusing mirror so the light is very spread out.

To check the voltage or charge the battery pull the switch out a little from the bottle to expose the terminals. Connect before the switch and the positive of the LED. Connect this to a wall charger. This allows you to charge the flashlight and check the voltage of the battery with the LEDs disconnected.

Step 3: Charging

I added two small charging wires (one before the switch the other on the positive before the LED).

I can simply hook up alligator clips to the wires to charge. I do need to have a timer and check the voltage often so it isn't over 4.2V. I can easily check the voltage of the flashlight without opening it using the charging wires to make sure the voltage doesn't get too low.



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    4 Discussions


    i recommend these they have charger and protection circuit all in one also a rister on the led will stop over current and wasteing alot of power by heat


    4 years ago

    Nope just a 5v 350ma transformer. I think its pulling about .7a it seems to work. I have charged over 200 18650 batteries and have never over charged any. I will be building an Arduino charging circuit soon.