I have a rechargeable flashlight plugged to an always hot 12v in my car. If the flashlight is not always charging and if left on the charging cradle it seems to discharge the flashlight battery rapidly so I choose to have it hot as to always have the flashlight charged. The obvious problem is that if I dont drive the car for four or five days, it drains the cars battery. There must be some sort of 'timed transistor' (for lack of knowledge of what such a thing may be called) available that would allow power to the unit for a certain amount of time, (say 72 hours) then cut power until its interrupted by either starting the car or pulling the light of the charging cradle. I got the idea from my wireless sony headphones that automatically stop charging after 16 hours I guess to preserve the battery life. Can someone help me with any ideas and what type of circuit or switch etc. I would need? Many thanks in advance!