S Keith: In another thread that went a bit sideways, you posted the following which is of great interest to me.:

"In some cases, the car itself is draining the battery. I don't recall the specific reason, but I think it was ignition switch related. If it doesn't drain the battery in one or more of the above cases, then it's likely not the battery itself."

Could you please expand upon that issue? I have a 2009 FEH with 78K miles with a replacement used HVTB from a 100K 2009 FEH.

A couple of years ago I had the common intermittent ignition switch issue where one had to push the key in to get the vehicle to start.

Rather than replace the entire ignition module, I went this route:

While that resolved the push in the key to start issue, it created a new one. Sometimes after the key was completely removed from the ignition, when I opened the door I got the warning sound one gets when leaving the key in the ignition. If you lightly bang the lock cylinder, you can make the warning tone stop. If you bang on the lock cylinder again, you can get it to make the tone again, even with the key nowhere near the ignition. Sometimes when I open the driver's door, I'll get that same warning chime, again with the key out of the ignition.

The reason I ask is due to my HVTB randomly draining overnight.to the point I have to charge it with your charger. Other times it will take a week and a half to drain that far. This happens even if I keep a high end battery maintainer on the 12 volt battery...(Battery and maintainer are Odyssey.)

Obviously, the first thing that came to mind is a failing HVTB, but I found the randomness to be odd.

If the car's electrical system mistakenly "thinks" the key is still in the ignition, could that keep something that draws power from the HVTB energized to the point it would drain the HVTB?

Hope this made sense and thank you for your help.

 

It is very likely your experience that was in my head when I typed that.

The cylinder replacement is considered a temporary solution. I have encountered others that conducted a similar repair and the results were short-lived. Ignition lock module replacement is the fix.

A random drain would seem to be unrelated to the HVTB except in the following scenario... that I see a lot of in Phoenix:

1) Hot battery is limited to a very low charge.
2) Hot battery is maintained in the vehicle at a very low state of charge due to 1
3) 1-2 overnight sits of a battery subject to 1 and 2 can push it over the edge

If your A/C is working well, and the battery stays below 90°F, then the above rarely happens.

On the occasions that the battery has discharged, have you recorded Pack voltage and DEL_MOD_V values? A high DEL_MOD_V value indicates cell failure.

I would not expect the maintainer to adequately maintain the 12V if there's an actual load on it. I find that even my 10A charger struggles to keep up with key on-engine off drains.

IMHO more data is needed. Options:

1) disconnect 12V every night.
2) disconnect data cable every night
3) disconnect main cable every night

Doing all three of the above for 30 days, i.e., isolating the HVTB from the vehicle and removing the possibility of any drain by the car, with ZERO self-discharge/charge events would indicate the vehicle is draining the HVTB vs. the battery losing charge on its own.