Unexplained battery drain overnight. Heard a noise once while van was warming up. Sounded like grinding noise. Sort of like trying to start a running engine. Rushed outside to find white smoke steam like smoke coming from unber the hood. Shut the van off immediately. Tried to start the van later with no sign of problem. Ever since the van has been draining overnight. Had it checked and noone knows whats wrong. Battery tests good, but it should since it is brand new. Starter and alternator check out ok. No visual corrosion on any wires or terminals. Driving me crazy. Cannot drive the van for fear of being stranded. I have seen many complaints about his on the 2008 Odyssey. Honda where are you on this. Obviously this is a problem that you could help with. I must assume that when someone complains that there are at least 10 others behind them that have not complained. I am a loyal Honda customer but now have my doubts.

Update from Feb 7, 2015: Today I removed the starter and had it tested. The starter is fine. There is no corrosion or loose connections associated with the starter. Next think to try is the ac unit. I have seen a few lostings about ac unit problems causing a battery drain problem. I'll post more updates as I go.

Update from Feb 15, 2015: After lots of searching online, I found someone with the same problem that had followed up with the solution. I encourage you all to do the same.

The problem lies with a relay that goes bad (gets stuck in the closed position). The A/C compressor relay. I bought a new one from Advance Auto for less than $7.00and it has worked fine ever since. Thefunny thing is that it is a genuine Honda part in some other box. It was suggested online that you buy the Vietnamese relay that is made by Mitsuba instead of Omron. The original part # is G8HL-H71 Omron or 39794-SDA-A03. The Mitsuba relay that is suggested is a 39794-SDA-A05. I still have to check the specifics of the relay to see if they match but looks to be the same. Right now the $7.00 Omron is working just fine. No more problems for one week. Thanks to the person who wrote a follow up with solution. Hope this helps someone else in the future.

Battery keeps dying early w/in a year. Diagnosed a few times w/o answer. no battery drain... Several replacement batteries. Turns out people with this also have another problem... white smoke and loud grating noise under hood. Not steam from radiator but large sudden discharge. That is from the A/C unit discharging gas from over running. The a/c electrical relay sticks in the on position and ruins the A/C clutch which winds up over running the A/C. This uses lots of battery and kills them. Check the A/C relay!!! Mine was repaired, but now it is happening AGAIN!