I'm geeking out (EE here) while doing some precision testing on some used Headways and I have noticed one cell is losing about 2-4% capacity every cycle, and it's nominal voltage during discharge was lower. So I captured it's discharge curve at 2C and compared it with another cell also at 2C. Both cells originally tested the same capacity, but you can see how this bad one, in orange, is now lower capacity, and you see how it's curve is 0.1V lower than the other. What phenomenon can cause such results in a LiFEPO4? Electrolyte oxidation from over charge? Design defect? I'm assuming this cell isn't going to last many more cycles, and it has a high internal resistance (explaining the 0.1V lower voltage) but I do not have a way to directly measure that.