I charge two batteries for my Tiny Whoop in my upstairs room. I take both down to the basement. I fly in my basement for one pack. I set the batteries down and let the motors cool down before putting a battery back in and flying for another pack. My Whoop mysteriously cuts off mid-flight. I thought it was a damaged connector at first. I check the voltage on both batteries upstairs and one of them is still at full charge. I flew a battery into oblivion because I accidentally picked up the same one for both flights. Label your batteries.