title_body: At what per-cell voltage should I land? I built 5" quad and I'm using 4S 1300mAh LiPo batteries. My question is: at what voltage should I land? Let assume that I'm trying to land when my battery is as low as it should go without causing damage to the pack.
upvoted_answer: I start my landing approach when the average cell voltage reaches below 3.5V on a stable flight (not counting voltage dips on short, aggressive maneuvers).
  
  At that point, you should still have enough authority to land safely. You can go somewhat lower without damaging the cells, but at that point, the voltage curve starts to be very steep and it is increasingly easy to slip below dangerous levels.
  
  I wouldn't advise landing on 3.2V simply because it's too easy to overshoot and to me, it doesn't give meaningful airtime over landing at 3.5V.
  
  Also, note that there can be a low voltage cutoff set up in the ESC that you probably don't want to trigger while in the air.