I've had Bluetooth OBD dongles in my newer cars (Crossie, Jeep) for five years and have left for over two weeks with no issues. Good one will shut down until awakened by ignition.


Also my computer cars run about 20 ma when shut down. Spec says "under 50ma", 200 ma will kill a battery in 3-4 days, 2000 ma (2A) overnight. Cars I do not drive often stay on a little float charger.


Used to have to change at least one battery a year until I switched to AGM. They last much longer.