I realize I’m chiming in almost a decade later, but I’m noticing the same issue with my 2006 RX330 (SUV). The first time this happened, I’d left a charger in the lighter/outlet-thing. However, the previous owner said they’d done that before and never had any issues.
Most recently, due to the coronavirus pandemic, we’ve just kept it in the garage the whole time, and just take my wife’s car for grocery runs (different type of car). I went downstairs yesterday to start up the Lexus and get the fluids running, and found the battery next to dead. At first, it did the rapid clicking sound it makes when trying to turn over a car with a next-to-dead battery, but now, the horn won’t even sound & I have to lock/unlock it with the key.
No lights are on, no modules, nothing’s plugged in anywhere, and the keys are far away from the vehicle when not in use. There is a clicking sound coming from a box under the fuse box (under the hood). Also, the lights around the ignition, and the light in the side compartment, flash every second.
I’m neither an electrician nor mechanic, so much of what’s been said (between the drama) in the previous comments are like reading another language to me. I’m hoping that someone’s figured out what it is since the previous comments 8 years ago. Thanks.