It’s been a great car, no trouble and over 100k miles on it. But tonight, I went out and realized that the inside lights were still turned on (after I’d closed and locked it several hours ago). Went out, everything seemed fine, but the inside lights just wouldn’t turn off - so I manually turned off the dome lights, but the map lights wouldn’t go off. OK, quick fix for tonight, I took out the bulbs… And then realized that the cigarette lighter (where I keep my phone charger) was still on. Sure enough, plugged my phone in, and it started charging… Usually, the moment I turn off the car/pull the key, power to the phone stops. So - something is wrong, but I don’t know what, and I don’t know how to fix it. I’ve removed the car charger from the cigarette lighter, and am just hoping the thing will start tomorrow… But in the meantime, does anyone have any ideas of what’s going on? Hoping for a quick fix a novice could handle. 
Thanks!!
At a guess, I’d suspect the BCM (body control module). When you shut the car off, the interior lights stay on for a while on most cars, then will slowly dim. Or are yours the type that stay on and then suddenly blink out?
I might start by resetting the BCM. Check with an expert, but on my car this simply meant pulling the 12V battery’s negative cable, waiting for 30 seconds, then reconnecting. On my latest car, I can go into the menu screen and select options for how long accessories stay on. I don’t think yours has that option, does it?
My former car (a 2005) did exactly the same as yours at least 3 times in 13 years. Twice I caught it (by accident) and I think it may have accounted for the battery dying a couple times… drained so far it couldn’t recover.
I don’t know your car, but that’s what I encountered.