We left our RDX (2008 model with tech) in parking garage for five days. When we returned the battery was completely dead. We got TLC jump start and it has run OK since.

I browsed this forum and found a long thread in 2007 with this issue, but no difinitive resolution. Then I ran across an Acura service news bulletin about a problem in the B-CAN system where it won't go to sleep correctly sometimes and causes excessive parasitic draw. Has anyone else had this problem?

 

This TSB is all I could find on the issue, even though it is for 07 it couldn't hurt to check it out.

http://www.in.honda.com/Rjanisis/pubs/SB/b07-064.pdf

 

My 2008 RDX tech had the same problem. It died twice this late winter, and early fall. Once before I added an iSimple PXAMG iPod interface--highly recommended-- after listening to the stereo for a half hour while the car was off, and once after I installed it.

I took it to the dealer after the second time, and they put an impedance coil on it for a few hours and said it was fine, and well within spec. It successively died for a few weeks after, and I had to charge the battery with a charger 3-4 times. Clear that this was not normal, I called the dealer unsatisfied, and he changed the battery to one with a higher capacity. I re-looked at my wiring for the powered antenna on the iSimple I connected, and voila--put it back on the switched power from the head unit, and never a problem since. It was drawing current from the battery while idle.

My conclusions from this experience:
1. There are fairly small energy reserve tolerances in the system, with a hefty power draw at baseline, presumably for the electronics. Don't get caught in the cold listening to the stereo for a long time with the engine off.
2. To be within spec via the impedance coil gave me no joy, no solution, and no confidence in the dealer's ability to find my mistake.
3. Never to underestimate my ability to goof up a process I do rarely or that is poorly documented.