If the engine is warm, it won't need as much juice to crank and start (unlike winter when evrything is frozen solid). Sounds to me like a bit of parasitic drain. Check to ensure everything is turned off (Dome and other interior lights). The OBS don't have as many computers that could stay on as the nbs, so, it's probably something easy like that (hopefully)... You'll probably have to do the checks on the individual circuits though to ensure there is no large draws while the vehicle is off. Just be sure to wait atleast 20minutes after shutting down to ensure all the computers have gone to sleep, or you'll get false readings.