I had it happen when I parked the car for a few weeks, and for some reason, the battery maintainer had turned itself off. What I got was a taste of what would happen if I had used a battery disconnect. I don't ever want to go through that again. The car did nothing when I pushed the start button; the battery was truly dead. I eventually boosted the system to get it started. Not only did I have to go through all my settings, I had to sign into the system and even resubscribe to a service I already had. Inconvenience is not an adequate word. For those not here to flame me for whatever I say, I am sharing my experience so that it could help someone in a similar situation.