12V System Charging System Problem

The BMS is protecting the HV battery from discharging in cold temperatures. At certain temperatures the BMS prevents, or minimizes, the rate at which the battery can be discharged. The HV battery charges the 12V battery.

I suspect that you are experiencing a temperature related issue.

 

I'd try to push for warranty coverage for whatever turns out to be wrong. My son got lucky and avoided a large expense with his BMW when it was just past the warranty period. Definitely worth trying if it turns out to be anything of consequence.

 

You reported several voltage readings above...
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. I am wondering if the subsystem that charges the 12V battery from the HV is bad. I think there was another form member who had to have that replaced.

I tend to think your situation was not cold enough to trigger the self-preservation functions (certainly not with 30/40 in the garage, and 20 outside).

 

Since maintenance mode starts the engine, it would appear that he confirmed an issue with the HVB not charging the 12V as he reported 11.9V in maintenance mode.

 

If warranty claim will not happen, you can always avoid replacing that expensive charging converter thingy with a cheap generator taken from a car wreck yard:

 

Nothing special - just recharge the main battery while you driving, typical perpetuum mobile, never need to use charging station again

 

I believe that’s the 3rd HV battery replacement for members of this forum.

 

What will the warranty be on the replacement battery?

The warranty for the replacement battery in my 2006 Insight was 3 years, rather than the 8 years on the battery that came with the car. In 2014, new Honda Insight battery packs were no longer available at any price so Honda was refurbing old battery packs by replacing any of the NIMH D-cell batteries that tested bad. The refurb pack lasted 5 years, so I got a better refurb from Bumblebee Batteries. Then I sold my beloved Insight when I found out that many other parts (eg. shift linkage) were no longer available from Honda.

 

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.

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?

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.

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.

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.

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.

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

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.

 

A 12V FLA battery will show a drop in voltage while under load. 11.5-11.9V is not unusual. Clearly the DC/DC charger is not working properly. I’ve measured ~14V with the car powered up.

Did you happen to measure the voltage an hour or so after driving the car?

 

This is correct. The replacement battery needs only to exceed the capacity threshold specified in the warranty. It could, theoretically, be as low as 37Ah. However, the replacement battery would be covered as if it were the original battery, 8yrs/100K miles from the date the vehicle was originally placed in service, in this case. So Honda, likely, although they have made some peculiar decisions, wouldn’t install a battery with a low capacity rating, knowing it would still be under warranty for 5 more years.

 

I agree they would not toss in a battery with low capacity. I was thinking more like possibly low 50's or something. I tend to think that during a refurb they might not replace all of the cells, only ones below a certain limit, thus leading to a reading starting out of something slightly less than 55, which would be an indication that a refurb was used. Which also means that not all of the cells are new, which means life expectancy would not be quite as long as a brand new battery. But then again maybe they do replace all of the cells, in which case it wouldn't really matter as it would be pretty close to being a new battery at that point. But still it would be nice to know for sure what they do in these situations. I guess we have just become conditioned to sleeping with one eye open when it comes to Honda.