Put your thinking caps on for this one [update]

UPDATE: Kia service says bad battery. They’re charging me 20%+labor to install. They also want to do fuel injector service and coolant service they say both are regular maintenance items I’m at 35k miles

Original post: Whenever my wife’s Sedona is left without starting for more than a day, the battery goes dead, as in nothing will click, beep, or glimmer. I have to charge it up or jump it, and then all is good, as long as I don’t let it sit for two days.

I’ve taken it into the dealer, but they can’t find anything wrong. Of course, by the time they see it, the battery is charged, because I charged it to get it there. I know there is a leak somewhere in the electrical system, but I don’t have any idea how to chase it down. Thoughts?