I had to call Lexus Roadside Assist Tuesday because my battery went dead. I was downloading music and typing for about 45 minutes with the engine off and the lights on. No warning, just had the hdd gone down, then the lights in the car went down and that was it. Lexus Link worked for about 5 minutes then that went out. Roadside assistance was there in 1 hour to jump me.

The reason I left the engine off this time was that I knew I would be out for awhile and did not want the car to idle for so long. In NY you can get a ticket for idling for too long. I knew I would not get a ticket, but I thought I would be burning a lot of gas.

Go figure.

Anyway, be careful when spending too much time with the engine off working on the car.

 

Yeah, gotta be careful not to drain the battery with all the gadgets. A fellow LS 430 owner of mine nearly had the same thing happen when configuring her NAVI system. After 45 minutes+, the lights dimmed, NAVI system shut off...fortunately she started the engine and charged the battery back up that way.

 

Your headlights most likely caused the majority of your problem... you were likely using around 150 to 200 watts continuous if you had them on (~100-120 for the front HID lights, plus some for the fogs, corners, and tails). And that's not like listening to a "___ watt stereo" with the battery off or anything because those watt ratings are only achieved with the volume cranked and the peak moments in the song when the bass hits, and such. Normal radio listening not considering a navi screen and such is likely lucky to hit 20 watts.

I thought, though, that the Lexus cars were supposed to be smart enough to shut the car down before the battery went completely dead as to allow enough juice to restart the car?

 

I was downloading some songs into the HDD with the engine and lights off (inside my garage), after about an hour everything shutdown.The steering wheel went back as if I had switched things off. I could power everything up immediately and the CD played on.

It must be a safety feature to prevent battery drainage because the same thing happened when I was uploading my phonebook.