These items are priceless. If you're like me in South Florida and you're out FPV and you're interrupted by rain, call the phone or whatever, it's not the time to fly. Just throw these guys at these batteries. Did. As simple as closing the batteries (if you use them). I have a pair of XT30/XT60 and all four work surprisingly well. Always determine the correct number of cells. great logic/code in them! Thank you WiFi!