What is "greater than normal" battery degradation?

[TomL]

My 2018 Touring model has 29,200 miles and I estimated my battery degradation was about 10% this summer but I fear it has worsened. As winter weather hit Wisconsin lately my SOC is about 20-25% lower than the same weather conditions last year. Today, my SOC is 35 in an attached garage at 40+ degrees with outside high and low temps from 26 to 35 degrees. I got fewer actual miles (<35) upon driving on wet roads. Based on last year's experience my SOC would be about 43-45 and I would get that many actual miles of EV driving.

Assuming my driving routine has remained relatively consistent and setting aside the caveats about SOC influences from driving behavior, tire wear, temperature affects, etc., I have two questions. First, should I expect the battery degradation to progressively deteriorate in a continuous downhill manner or is it likely to have plateaus where it stabilizes for a period of time?

Second, how much battery degradation has to occur before making a warranty claim? Honda dealers in this region don't know a Clarity from a lawn tractor and would need "guidance" about how to check the battery's condition. I seem to recall someone on this forum describing the specific test any Honda dealer can run and what capacity indicates warranty consideration. Are you out there and willing to offer counsel?

 

[petteyg359]

You are conflating SOC and "GOM" (guessometer).

Warranty is at 65% off the top of my head.

 

[Mowcowbell]

Tom: You can't go by the guess-o-meter. Only way to measure battery degradation is to take the vehicle to your Honda dealership and connect their diagnostic computer to the ODBII port. It will tell them the current battery capacity of the main traction battery.

 

[MrFixit]

I seem to recall someone on this forum describing the specific test any Honda dealer can run and what capacity indicates warranty consideration. Are you out there and willing to offer counsel?

Yes... The warranty is based on the battery capacity as measured by the vehicle itself. The initial capacity is around 55 amp-hours, and the warranty applies if the capacity drops to below 2/3 of this (or, 36.6 amp-hours). The only way to know this number is, as stated, to get your dealer to read the value from the vehicle through the OBD2 port.

Also, as you allude, do NOT assume the dealer will know what to do. If you ask for a battery test, they will undoubtedly measure your 12V battery and give you useless information. My recommendation is to print out the last page of the attached PDI document and hand that to the service manager. It clearly defines what is needed.

BTW - the battery warranty is 8Y, 100K miles unless you live in one of the following states (in which case it is increased to 10Y, 150K miles):
California, Connecticut, Delaware, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon
Pennsylvania, Rhode Island, Vermont, and Washington.

From my experience, there is some initial degradation, then it plateaus. Based on the amount of energy required for a 'full' charge, I started at around 14.5 kWh, and it went down to ~13.5 kWh where it has been holding steady. This implies a 7% drop. I have a 2018, purchased in 11/2018.

 

[TomL]

Yes... The warranty is based on the battery capacity as measured by the vehicle itself. The initial capacity is around 55 amp-hours, and the warranty applies if the capacity drops to below 2/3 of this (or, 36.6 amp-hours). The only way to know this number is, as stated, to get your dealer to read the value from the vehicle through the OBD2 port.

Also, as you allude, do NOT assume the dealer will know what to do. If you ask for a battery test, they will undoubtedly measure your 12V battery and give you useless information. My recommendation is to print out the last page of the attached PDI document and hand that to the service manager. It clearly defines what is needed.

BTW - the battery warranty is 8Y, 100K miles unless you live in one of the following states (in which case it is increased to 10Y, 150K miles):
California, Connecticut, Delaware, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon
Pennsylvania, Rhode Island, Vermont, and Washington.

From my experience, there is some initial degradation, then it plateaus. Based on the amount of energy required for a 'full' charge, I started at around 14.5 kWh, and it went down to ~13.5 kWh where it has been holding steady. This implies a 7% drop. I have a 2018, purchased in 11/2018.

Thanks MrFixit, exactly what I was asking for.