18650 lithium battery has two voltages, the nominal voltage of lithium iron phosphate is 3.2V, and the nominal voltage of other materials such as ternary is 3.7V.
To assemble 12V lithium battery, if it is a lithium iron phosphate material, it needs 4 strings, that is, the negative pole of the battery is connected with the positive pole of the next section and so on. The positive pole of the first section is the positive pole of the battery pack, the fourth section The negative electrode serves as the negative electrode of the battery pack. His voltage range is 8-14.4V; the ternary material is similar to just a few, and the voltage range is 9-12.6V. The above two voltage ranges are calculated by adding a protection board.
There is one more thing to note about the lithium battery combination, because lithium battery itself has no way to overcharge. Over-discharge and short-circuit and other related protection, so you must add a protection board.