Electrical Question-Breaker panel does not cut all power

Hi folks. Another understanding "new school" technology question. Dealership did supply new battery when we picked her up this spring. It's a cheap starter battery, but another time. We have come home from a few trips now and parked it on the drive. I go out in a few weeks and all is dead. I check the front mounted battery and it is dead so on the charger it goes. Let me say that we dry camped with a genny once and had full hookups another time. So the battery wasn't taxed while in the campgrounds, Happened again. Back on the charger Everything dc is running while on the charger. Ok fine. There is some draw while parked, so I should turn off all the breakers. But I notice the onboard stereo is still lit and the thermostat is still lit with all breakers off. Might there be an isolation switch I haven't found? I disconnected the ground on the battery. I'll be upgrading that anyway. Thoughts please.