Battery dying overnight on 04 HCH

I am suddnely having the same problem with my 2003. I have had it in the shop three different times in the past month because of this. I was sure that the battery under the hood had given out, since jumping or charging that battery solved the problem, but the dealer insists that the battery is fine.

They have been unable to replicate the problem in the shop. It will die over night, or sometimes within a few hours after it has been turned off, even though it showed more than half a charge. I will take it to the dealer, it will sit over night, and it starts right up. Take it home. Dead. I finally told my dealer to keep it until it dies. Of course, I still think that front battery is the culprit, although it is VERY inconsistent.

After it happened once, a month ago, it didn't happen again for three weeks, then it happened twice on consecutive days, and now it won't die again.

Has anyone been able to diagnose and resolve this problem?

Thanks. The dealer called me today to say that he is "guessing" that is preceisely the problem. I was a bit reluctant to have him do the work, but perhaps we'll take our chances, since he is only charging us for the part $22.

I agree it could be a sticking relay that is causing the problem. Since the radiator fan runs for a while after the key is turned off, it is the mostly likely suspect. Also relays are very easy to change.

I've started experiencing this same problem starting about 3 weeks ago. One day my IMA light came on. I restarted the car, and it didn't come back on. That night, the batteries drained completely. I had to jump it the next morning. It didn't happen again for about a week, then it happened 2 days in a row. I bought a new accessory battery, and now about 5 days later, I woke up to a dead car this morning. I have been trying to determine a pattern, and it seemed at first it was dying the night after I commuted home on an especially hot day, or wet day. However, yesterday was not the case. The relay sounds like a viable culprit. I will be going to the dealer soon.

Any one else have input before I end up (hopefully not) dropping tons of money on this?

I have a 2007 HCH, 3000 miles on it. Already had the standard battery replaced when we kept finding the car each morning requiring a navigation system code. IMA battery was low. The dealer replaced the battery, saying that was the cause. Indeed, the car doesn't die overnight anymore. But I don't understand the relationship between the IMA batteries and the regular one. The service mgr says they're "connected" but can't say why, how, and when the connection does anything. He says they "back each other up" but what the heck does that mean?

I notice in these forums several issues around the regular battery and occasionally about the IMA. Anybody know just when one battery goes to work and when the other batteries jump in (aside from the motor assist mechanism itself)?

I left the key turned on in my hybrid. I'm told that you can jumpstart the 12 volt battery that turns on the computer board. Can this be done safely with out it hurting the computer board?