Free Rechargeable Flashlight From LEDs and Lithium Battery

Introduction: 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.

Apocalypse Preparedness Contest

Participated in the
Apocalypse Preparedness Contest

Guerilla Design Contest

Participated in the
Guerilla Design Contest

On a Budget Contest

Participated in the
On a Budget Contest

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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


    5 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.