We have a 2003 HCH which we purchased used over two years ago. For most of that time it has been a very good and reliable car. However several months ago the lights were left on and the 12 volt battery died. It had to be jump started. Beginning with that incident it has intermittently had a dead battery when you go out to start it in the morning. The dead battery occurrences became more frequent over time. We had the car to three different auto repair shops including a local Honda dealer and all said that nothing was wrong with the 12 volt battery, the charging system or the "big" battery. At the recommendation of the last shop we took the car to we had the 12 volt battery replaced "just in case it had a bad plate". The problem persisted. Upon reading this forum and others, I found the recommendation of disconnecting the 12 volt battery for 20 to 30 minutes to reset the computer. After the "reset" the car functioned perfect for almost a week before going back to having a dead battery almost every morning.
Other possibly related symptoms include:
IMA light comes on intermittently.
"big" battery is completely discharged the mornings when the 12 volt battery is dead.
Gas mileage had declined by 5 to 6 MPG until the "reset" was conducted. The MPG has rebounded by 3 to 4 MPGs.
If someone out there could give me some idea on what the problem is and potential solution(s) it would be greatly ppreciated. I thought it was the "big" battery but according to the local Honda dealership, it checked out fine.