My HV Battery Warranty Replacement Experience

Hello everyone, it's been a while since I have been on. I just had my battery replaced under warranty and here are the details.

In the beginning I really took care of and babied my battery. After the pandemic hit, however, not so much. Car was just off the boat when I purchased it in 2018. 15 months later the battery capacity was still high at 54.2%. That first year I kept the charge between 85% to 35% and never let it go below 30%. I fully charged it twice a week. Did 80% EV driving and 60% of the charge was on Lvl 2 and 40% was lvl 1. Took great care to park in the shade at work and in the garage overnight. Once the pandemic hit I worked from home and the car sat for 8 months rarely if ever being driven. I kept it charged at around 60% and trickle charged the 12v. Was not able to keep it garaged or shaded and didn't do a good job of keeping the windows down during the summer. So it sat through long bouts of 100F summer temps and some -5F winter temps.

About a month and a half ago I turned it on one day and all kind of warning lights popped up. When driving I experienced a couple of instances or sudden loss of power. Dealerships was backed up and it took about 3 or 4 weeks to get me in. In the meantime I did some digging.

The DTC's that came up were:

P144A HV Battery Pack Voltage Variation Exceeded Limit
P0A7F HV Battery Pack Deterioration
P0B0E HV Battery Pack Current Sensor B Circuit

I disconnected the 12v and left it disconnected for 2 and a half days and that did not clear anything. The battery capacity was at 48.4 ah after 3 years and 40,000 miles. After studying the data for a month with Car Scanner I determined that pack A was just fine. Pack B was the problem. The difference between the Max SOC and Min SOC was very small on pack A but miles apart on Pack B. See the first picture.




You may notice that the battery capacity shows 54.98 in the screenshot above. The reading was taken after I took it into Honda the first time. They reset the DTC's and magically the capacity went up from 48.4 to 54.98. Of course that is not possible but I imagine they reset the value so that the car could recalculate it from a fresh start. I don't know how long that would take but it never happened in the weeks I had the car before the replacement.

So as you can see while pack A is less than 1% apart pack b has a 30% gap. Even when fully charged the gap was never less than 5% Sometimes pack b would get stuck and not do anything. They car actually drove better when that happened even though I only had 20 miles of range:



I eventually found the culprit. 2 cells were throwing everything out of whack. They were B67 and B68. I made a chart of the Car Scanner data and as you can see 82 out of the 84 cells in pack b are right close together. The remaining 2 are the outliers and seemingly the main culprit.

Note that I scaled the next 4 voltage charts voltage range on the y axis and time steps on the x axis so that visually they are all apples to apples.


Pack B voltage by cell distribution





Here is pack A:




So the replacement battery finally arrived from California and was installed. I asked the service advisor to see if it was refurbished or brand spanking new. He said he check and it was brand new. I also asked him to check how long ago was it manufactured but he could not find that information. My thought is that its been sitting in some hot warehouse in Cali for a couple of years. I asked for the Electric Powertrain readout and the tech did a printout of it just after he installed the battery and was doing his checks. Here are some notable stats:

Capacity: 55.0 AH
Individual Max SOC 30%
Individual Min SOC 27%

Of the couple of hundred reading on the list everything was normal or in range except for Battery Charger VAC Low. It shows as "Failed". Not sure what that means...

So I fear that the battery has probably been sitting for a while and slowly discharging. Further adding to my concern is it looks like the beginning of the same problem is showing up in new pack B (maybe new pack A too). I checked many posts and saw that just about everyone who posted SOC data from Car Scanner both packs A and B max and min's were very close to each other and mostly within 0.3% of each other.

No such luck here. Before I drove out the parking lot I took a reading and pack A has 1.2% spread (93.01% vs 91.81%)...okay...probably not the end of the world. Pack B however has a 4.36% spread (94.78% vs 90.42%)....hmmn...

Here is the voltage of new pack B (remember this is to same scale as the 2 voltage charts above and one below):




Here is the voltage of new pack A




Oh well, there is nothing I can do about it for now but keep an eye on it. Maybe over time the cells voltage range will tighten up. I have had it for 10 days now and have "exercised" it a bit by fully charging it and running it down to 30% and the gaps still persists.

 

@MrFixit I went back in and reinserted the images. Hopefully that works. If not I might need to put them in a zip file and upload them. I haven't seen much balancing at the end of a full charge on the old battery or new one. There is always a gap. I have seen what appears to be passive balancing when the car is off. For instance say I have driven for a while and make a stop and the car is off for an hour. When I come back and look at the SOC's they are closer together then when I turned it off. Now that could be the difference between a closed circuit voltages readings after the battery has discharged to a proper open circuit voltage reading when I come back and turn the car back on. I still have a lot of csv files to export out of Car Scanner so once I do that maybe we can see a pattern,

 

There should be six images. Two Carscanner screenshots and 4 excel charts.

 

Dan,

Interesting point. I dug out my Killawatt and measure. I am getting a steady 121 volts and 16 amps. Charging at my house would not have any bearing on the new battery as it was just installed 8 days ago and I have only charged it 3 times. Also I recorded this data the minute I picked up the car before I left the dealership lot.


Sent from my iPhone using Inside EVs

 

I haven’t had the time to really dig into it since I figured out how to export the Car Scanner data recording. My work is in data analytics and statistical analysis so I am going to gather all the data into an Access database and see what correlations and trends I can identify.

A quick visual check may support your thoughts of a refurbished pack. There does appear to be a pattern in the 7 banks (12 cells each). In each bank the voltage of each cell is very close. When comparing banks as a whole it looks like banks 1,3,4, and 6 are within a tight range (3.678v +\- 0.005) and banks 2,5, and 7 are in another range (3.880v +\- 0.005).

From all the other max/min SOC readings that everyone has posted, I seem to have the largest variation.


Sent from my iPhone using Inside EVs

 

Her are the screenshots of the voltage reading I just took.


Sent from my iPhone using Inside EVs

 

Remainder of the original warranty. Dealership gives a 12 month warranty if the original has ran out.


Sent from my iPhone using Inside EVs

 

You make a good point. I need to be consistent in my measurements. Going forward I will collect open circuit voltage readings after a full charge and also at nominal 3.7v. Then I will compare full charge to full charge and nominal to nominal. By normalizing as such, I should have much more reliable data to analyze over time.