I bought a lithium iron phosphate battery for the assignment and found that it had 3 wires, so I disassembled it.
I checked that red is "+", black is"-"line. What is the yellow line?
Is it irrelevant if I use only black and red wires ignoring the yellow wire??
It says NTC next to yellow. And it's not visible in the picture above, but here the line goes down and a small part will be stuck to the battery.
In other words, yellow is a terminal that checks the temperature of the battery and detects it if it is overheated.
In general, it doesn't matter much even if you don't use it, but if it's a product that requires reliability, this terminal is checked to see if the battery is overheated, and if it is too overheated, it is used to cut off the current.