+1 on all the posts.
Best bet, if under warranty, go to dealer, do a drain observations with modules, go from there. Im pretty sure it's not a battery problem, but some module either short circuited or is on the fritz.
BMW and Mercedes Build Beta Products!
Lexus build Release Candidate Products!
Why does this matter?
CAUSE EVERY TIME someone says Lexus has better build quality, one should consider what Toyota their Lexus Engine and chassis platform comes out of and how long that part has been tested in the real world!