Did you know that once your key fob is about 8 ft. away, it is out of the range of your car's antennas (there's several on the car) and the CANBUS* will go to "sleep mode" and not communicate with it? As a result, there will be no drain on the fob's battery. If, for some reason, you have to store your fob within this communication range (e.g., in your garage), place it is a metal cookie tin or Faraday pouch/case to prolong the life of its battery. Despite this precaution, after 3 years, it is a good idea to replace the fob battery. The following thread explains this simple process: https://www.challengerforum.com/thr...dge-challenger-key-fob-battery.476/#post-3223 On a related engine battery matter, it's best to lock your car. This signals to the car's electronics that the car is not going to be used for a while and it can enter its lowest power mode sooner. Don't worry about the draw of the security system. It uses some power but it is not on all the time. It is switched on and then off every so often- every second or so- and it is on for just a real short time which reduces the power it consumes. *CANBUS stands for Controller Area Network bus. In the electrical sense, a 'bus' is a kind of connective hub that allows for communication between two or more circuits or components. A CANBUS is connected to - and so spots faults in many parts of a vehicle. For instance, low tire pressure may trigger an error message on the dashboard.