Here is the discharge curve of lithium....notice the "knee" at the very far right when it begins to bend. See how quickly it drops off....If you only use about 50 % of the battery, you'll never get to the knee. People who use BMS's, they use them for the reason that they want to know when they reach the knee, and so the BMS alerts them to when they've used so much of the battery that they've hit that part. I avoid using a BMS by just not ever using that much battery. (ignore the bottom values..this is for a very large lithium battery)