So many questions raised by this thread. Glad that it seems to be working out for you and that your car will be back into shape hopefully soon, at what seems to be no expense to you which will be great. Hopefully you can help us to at least attempt to figure out what was going on here, since one day all of our cars will go beyond the 8-10 yr/100-150K battery warranty, and some of us may still own our cars at that time.
She pulled into a nearby parking lot and the car died.
She was able to restart it a little while later, and made it to our driveway before it died again.
It's understandable that a car can get into a situation that it can't start. But if a car actually dies while driving this is of course very concerning. I don't know if I have heard before of a Clarity dying while running, so I am interested to know exactly what that means and what the symptoms were. For example was the display panel completely blank, no lights on the dash anywhere? Or was the display panel on but the car would not come out of park? I realize you did not experience this first hand and your wife may not remember all of the details.
I notice that in both cases listed above, it died after she pulled into a parking lot or driveway, not while actually driving. Is this just an amazing coincidence? Or perhaps the car was in a limp mode that allowed driving, but once stopped would not allow it to continue. One of the error messages that you attached said "Critical Failure Detected. Stop Driving When Safe". Perhaps this corroborates that theory.
Did you experience the car dying any other time other than those two?
Started car in maintenance mode and measured 11.9V at battery terminals.
Running in maintenance mode is sort of a moot point. The 12V battery is charged by the HV battery via the DC to DC converter. This occurs (or should occur) anytime the car is in READY mode, regardless of whether the engine is running.
I would be interested in the 12V battery voltage when the car is 'started' and in the run mode. When in that state, the 12V battery should be more like 13.5-14.0V
That's a good question but I'm pretty sure the results would be the same, when you are in maintenance mode the system is in READY mode and can be driven although it is advised to not do so.
I continue to get these errors whenever trying to drive the car and a short 1-2 mile drive depletes the new battery to below 12V, after which I have to put it on a tender to bring it up to 12.3V.
So this does indicate a problem with charging the 12V, which could be a problem with the DC to DC converter, but probably could be caused by other problems as well (including bad HV battery). In that situation your 12V system will be powered by the 12V battery while driving, and perhaps both incidents when the car died occurred when the 12V battery gave out (coincidentally and thankfully while already parked). With the new 12V battery you were able to do a short test drive, presumably if you had driven a longer distance on the new 12V battery it would have had the same result and the car would have died.
Possibly a problem with the HV battery could cause this, but if the HV battery was so weak that it couldn't even charge the 12V battery, then it would seem the car would only be able to crawl along at a few miles per hour. Or maybe when it goes into limp mode all power is directed to powering the wheels and it turns off the DC to DC converter, leaving the 12V battery to fend for itself, powering the 12V system for as long as it can, which of course will be for a limited time, thus the warning to "Stop driving when safe". I would think a healthy 12V battery in warmer weather could last at least a little while in this situation. An older battery in below 0F weather probably not very long.
Dropped car off at local Honda dealer yesterday. Problem has been diagnosed as a bad HV battery assembly and requires replacement of the entire assembly, which costs over $6k I was told.
So this raises the big question which I'm sure we will never get an answer to, which is what was the problem with the HV battery? We tend to think of individual cells failing, but I suppose there are electronics associated with the HV battery, but surely those can be replaced separately without replacing the entire battery? Or maybe not. Not so great if these electronics are subject to failure. Then again failing cells could cause all kinds of random problems and warning messages, so maybe there were defective cells. But I'm guessing that it's not easy to diagnose where the problem is, easier to simply replace the entire part. Of course in this case a very expensive part. But then again Honda is not paying retail, whereas we would be. Hopefully in a post-warranty situation there would be more diagnostics done before making a decision to replace the HV battery? Maybe that's wishful thinking.
Although I wouldn't be surprised if replacing an HV battery electronics module (if that were diagnosed to be the problem) requires removing the HV battery from the car. Maybe Honda, who I am guessing made the decision to replace the battery under warranty since they are paying for it, figured since the battery is coming out anyway go ahead and replace it so they could get the battery back, maybe they like to examine how the batteries hold up over time. Maybe that's unlikely, just a random thought, but it would be for us a more comforting explanation for why they decided to replace the entire HV battery if only a controller had gone out.
Good question! We purchased the car new just over 3 years ago and I don't believe they can shorten the existing warranty, so it would be nearly 5 years at the least. I will have to ask about that.
Anything covered under the factory warranty is covered for the entire warranty period, no matter how many times they replace something. However once the warranty is past then you have to pay for the parts, and there will usually be some type of separate warranty for the replacement parts
I will be asking for a capacity test too.
Please do! It would be great to get the reading on a brand new battery. Then again I have heard a theory that under warranty Honda might replace the HV battery with a refurbished one, which could in theory mean that you will start out with less than 55 Ah. Nothing much you can do about that but it would be good for you to know what capacity you are starting out with. There is actually an easy and inexpensive way to check the battery capacity yourself using an OBD-II Bluetooth reader. MrFixit has created a thread on this with all the details. You seem to be technically minded so I think you would like using it. It provides many other useful pieces of information as well including engine RPM, and various temperatures including cabin temperature.