Car will start but dies. Then battery is dead.

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. Hello, a start and stall, followed by no electrical power to crank the engine sounds like a possible anti-theft system activation. It's impossible for me to say without hands on testing performed at the time the failure occurs. It's an unusual concern, and I would not rule out influence of aftermarket items attached to the vehicle. I would recommend reaching out to a shop near you for guidance. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.