If you want to use 18650 lithium battery to light 20 LED beads, a simple way is to connect each LED bead in series with a current limiting resistor, and then connect them in parallel to the two ends of the 18650 lithium battery to light up. Since the questioner did not say which LED beads, here we take the commonly used white LED beads as an example, to introduce the specific circuit connection.
With a single 18650 lithium battery to light 20 white LED beads can be connected as shown in the circuit above, that is, each LED bead in series with a current limiting resistor, and then connected in parallel to the two ends of the lithium battery.
Here we assume that the 20 LED beads are low power high brightness white LED beads in straight package (see above figure), the working voltage of such beads is about 3V, and the large working current is 20mA, if used for lighting, the working current is generally 10~15mA.
The nominal voltage of single 18650 lithium battery is generally 3.7V, here we introduce the calculation method of current limiting resistance R, R = (3.7V-3V)/15mA ≈ 0.0467KΩ, in practice, you can use the nominal value of 47Ω/?W metal film resistor. In other words, a single 18650 lithium battery lights up 20 low-power white LED beads, each bead in series with a 47Ω resistor connected in parallel at both ends of the battery can be.
For red, green, blue and other colors of LED beads, you can also use the above method to light up. At this point we just need to know the working voltage of the lamp beads, according to the above method to calculate the resistance value of the current limiting resistor can be.
Translated with www.DeepL.com/Translator (free version)
