This is a led torch powered by 18650 battery (i use samsung battery 2600ma, 3.4v).
The torch contain 13 3W smd led, you can by here: https://www.amazon.it/gp/product/B07BVTNS6Y/ref=ppx_yo_dt_b_asin_title_o06__o00_s00?ie=UTF8&psc=1
For the cable i used some old arduino jumpers and i have not used any resistance, because the battery have the same voltage of the leds.
In the plug i paste some magnets.
All the smd leds are paste into the case, after the soldering.
At the base of the threadings I'm going to put some cables, because I want the light to be turned on by screwing it.
All the led are 3W, and I connected in parallel. You can see the circuit in the image.
Battery life of the torch is 20 minute.
To make the battery last longer, add resistors before each LED (1 to 10 ohms); But doing so, the LEDs will also make less light.