Battery Capacity Test Results

[czbo]

I have a 2019 Honda Clarity PHEV, purchased last September, so it's been about 1 year, 2740 miles. I am in upstate NY. I recently asked the dealer to print out the battery capacity from the diagnostics (after much explanation and showing the pre-delivery document service bulletin's instructions, otherwise they had no idea what I am talking about), and it was 54.1 Ah. Nominally 55 Ah. Using these 2 data points and the data point from Nicka2017, it would appear the battery capacity degradation is more a function of distance driven than age of the vehicle. Extrapolate to 100k miles, your battery capacity would be at 38.1 Ah and still within the threshold of needing replacement. See the plot.

of course, with only 3 data points, this should be taken with an extreme level of skepticism.

 

[MrFixit]

From my experience the battery degradation is NOT linear.
I have a 2018, and have observed that my capacity dropped by about 7% during the first year, but has held steady through the entire second year.
I am basing this in measured kWh input for 'full' charges.

I will add a caveat however that I only have ~19K miles during those two years (about 75% is EV).

 

[Pooky]

From my experience the battery degradation is NOT linear.

I agree, most scientific studies find exponential or quadratic models to match most closely. Degradation is mostly a function of battery cycling, temperature, and charging delta. So someone who drives 100k miles in HV mode will have less degradation than someone who drives 100k miles in EV mode.

Part of the reason why capacity decreases so drastically in the first phew cycles is because of the forming of a Solid Electrolyte Interphase (SEI) film, where certain active cells in a newly-operating battery will be consumed to form this film. As the film stabilises, less cells are consumed and capacity degradation slows.
https://www.researchgate.net/figure...d-the-fitting-of-the-SEI-model_fig1_303890624

Li-Ion degradation is highly dependant on charge cycling, temperature, and charge delta. Firstly, as shown by the test data here, even after 1,000 charge cycles at 1C speed the battery has only lost about 9% SoC in the worst-case scenario tested (100% to 10% [10% being the car's HV buffer] is not shown but it would be very close to 90%). There are about 250 working days in a year, and if we assume that for each of those days the battery is cycled from 10%-100%, the battery should have only lost ~7% in the first two years and about 10% in the first four. At least that is true for a 20C mild climate.

Temperature also has a negative effect but mostly in hot climates, such as Arizona (remember the Leaf fiasco?). The graph below describes the degradation behaviour of batteries when kept at 50% SoC at various temperatures over time. Keep in mind, this is degradation without any active cooling or cell cycling, so this data would be more representative of a Clarity sitting in a dealer lot than anything else.

In the same vein, empty batteries sitting on dealer lots would suffer from greater degredation regardless of temperature, though unfortunately this study did not test SoC below 60%.

@Nicka2017 Overall, the point is even if you were doing all the wrong things to your battery, 20% degradation in a year is a defect and not normal. Hopefully it continues to degrade to the warranty threshhold before it expires.

 

[Ss84]

I just got a report on my car today (after digging through this forum and showing examples of what report I was even talking about): 46.8Ah on a 2018 PHEV bought in December 2017 (so not quite 3 years old). It has 28,100 miles and it feels like I've lost a lot of range. I used to be able to get to work and back (just over 44 miles) easily in summer, and now it takes effort to barely make it. I've contacted Honda about it but I'm not really expecting anything to come out of it. Seems like an unacceptably high loss if it started at 55Ah (which I'm not sure about). I only asked for the report today because it "felt" like the range was getting noticeably bad and the report seems to confirm it. I've only filled the tank once (so used the gas the car came with, put gas in once, and I'm still at half a tank). IE: Almost 28,000 miles of all EV and no HV (other than one trip to the emergency room and all of the times it turns itself on to cycle fluids and/or the SoC is "full" and it spins up the engine when slowing down- though I've basically learned how to avoid that after the first year).

I'm definitely interested in the "inner stats" like everyone else here (disappointed in how black box this car has been and that you can't get anything as simple as a % SoC instead of just bars or a readout in kW or Ah). All I have is a cheap bluetooth OBD dongle so I probably can't be of much help but I can provide the first two pages of my report from the dealer if it's useful (they didn't give me the other 4).

 

[AREED]

After a full charge i tested battery capacity at 50.1ah. 2018 with 26500 miles.

 

[ICanBreakIt]

My dealership told me it read 54.6 ah. My clarity is a 2018 with 15,000 miles. I had to drive 30 miles to dealership so battery should've been nice and warm when it was measured. I wonder if some of you are getting low readings because the battery wasn't warmed up first.

 

[MrFixit]

I would bet that the battery capacity is integrated over time, and not vulnerable to the current conditions of charge level, temperature, etc. Once we are able to get more owners to be able to read this value themselves we will likely learn more about it.

Since it is the fundamental parameter determining battery warranty, it needs to not be vulnerable to these kind of changing conditions (or it needs to adjust for them). Honda can't have a situation where a warranty replacement is triggered because it is especially cold out, or if the customer comes in with full or empty battery...

 

[PHEVDave]

I would bet that the battery capacity is integrated over time, and not vulnerable to the current conditions of charge level, temperature, etc. Once we are able to get more owners to be able to read this value themselves we will likely learn more about it.

Since it is the fundamental parameter determining battery warranty, it needs to not be vulnerable to these kind of changing conditions (or it needs to adjust for them). Honda can't have a situation where a warranty replacement is triggered because it is especially cold out, or if the customer comes in with full or empty battery...

Yeah, it would seem that this is probably not an instantaneous reading but rather something stored in a non-volatile location and updated periodically.

 

[Landshark]

I watched a 30 minute video yesterday that covered the key points of more than a month of battery capacity tests on lithium, AGM and Flooded LA batteries at various temperatures and loads. It was performed at the Battle Born facility in Reno, NV and was intended for the RV industry. In particular, for how they perform as house batteries in a motorhome. I now have just enough information to be dangerous.

One of the more interesting statements, to which I hadn’t previously given much thought, was that the aH rating of a battery is a measurement of charge, whereas the kWh rating is a measurement of energy. Perhaps the Honda software monitors the level of charge that the battery has accepted over the past 5, 10 or 20 charges? Interestingly, in some cases, the Lithium batteries were able to provide more than 100% of their rated capacity in kWhs.

The gentleman who conducted the study suggested that battery capacity be expressed in kWhs as an industry standard. The issue with aH’s is that we have to get Volts involved to determine kWh’s.

The Clarity is ~54aH’s at 310V.
My solar backup is 350aH’s at 48V.
The motorhome is ~800aH’ at 12V.

Which has more kWh’s?
The last 2 are Lead Acid, so less than 100% of that capacity is available. If they were all Lithium, the first two could provide ~17kWh’s. The last is 9.6kWh’s. Realistically, the solar batteries can provide 10-12kWh’s as they are programmed to go as low as 25% SOC. The coach is at 50%, so they can provide less than 5kWh’s. They’re old and tired and will be replaced with Lithium this summer.

Guess I wandered if there a bit. I’ll be due for the annual oil change and tire rotation by March, so I’ll ask for a capacity test at that time.

 

[PHEVDave]

I watched a 30 minute video yesterday that covered the key points of more than a month of battery capacity tests on lithium, AGM and Flooded LA batteries at various temperatures and loads. It was performed at the Battle Born facility in Reno, NV and was intended for the RV industry. In particular, for how they perform as house batteries in a motorhome. I now have just enough information to be dangerous.

One of the more interesting statements, to which I hadn’t previously given much thought, was that the aH rating of a battery is a measurement of charge, whereas the kWh rating is a measurement of energy. Perhaps the Honda software monitors the level of charge that the battery has accepted over the past 5, 10 or 20 charges? Interestingly, in some cases, the Lithium batteries were able to provide more than 100% of their rated capacity in kWhs.

The gentleman who conducted the study suggested that battery capacity be expressed in kWhs as an industry standard. The issue with aH’s is that we have to get Volts involved to determine kWh’s.

The Clarity is ~54aH’s at 310V.
My solar backup is 350aH’s at 48V.
The motorhome is ~800aH’ at 12V.

Which has more kWh’s?
The last 2 are Lead Acid, so less than 100% of that capacity is available. If they were all Lithium, the first two could provide ~17kWh’s. The last is 9.6kWh’s. Realistically, the solar batteries can provide 10-12kWh’s as they are programmed to go as low as 25% SOC. The coach is at 50%, so they can provide less than 5kWh’s. They’re old and tired and will be replaced with Lithium this summer.

Guess I wandered if there a bit. I’ll be due for the annual oil change and tire rotation by March, so I’ll ask for a capacity test at that time.

Here’s a cool idea. Somebody could design a CANbus monitor that monitors all activity on the bus and records it. Take the Clarity in for a battery check and record the query that asks for that information so that it can be duplicated. I’m assuming it just involves a query made over the CANbus with a response.

 

[DucRider]

The Clarity is ~54aH’s at 310V.
My solar backup is 350aH’s at 48V.
The motorhome is ~800aH’ at 12V.

Which has more kWh’s?
The last 2 are Lead Acid, so less than 100% of that capacity is available. If they were all Lithium, the first two could provide ~17kWh’s. The last is 9.6kWh’s. Realistically, the solar batteries can provide 10-12kWh’s as they are programmed to go as low as 25% SOC. The coach is at 50%, so they can provide less than 5kWh’s. They’re old and tired and will be replaced with Lithium this summer.

When you are comparing the LiIon to the lead acid are using nominal voltage vs fully charged voltage.
The Clarity battery pack when fully charged is 348V. The energy (kWh) is derived from the rated Ah x nominal voltage (essentially average voltage from fully charged to fully discharged).
The discharge rate, along with temperature, will impact the Ah (and therefore kWh) available. Battery capacity ratings are at a specified temperature and discharge rate after fully charging to a set voltage at a specified C rate with a designated rest period before discharging to the lower cutoff voltage. Battery capacity is actually a variable.

 

[MrFixit]

Here’s a cool idea. Somebody could design a CANbus monitor that monitors all activity on the bus and records it. Take the Clarity in for a battery check and record the query that asks for that information so that it can be duplicated. I’m assuming it just involves a query made over the CANbus with a response.

Although you could theoretically do this, there is a better way. Perhaps you haven't seen this thread.
This device is low cost in the scheme of things. Even if you were inclined to try and reverse-engineer the CAN traffic (far from trivial), it would be way easier to do it using the AP200 because you don't have to navigate around the dealer and 'hide' your CAN sniffing activity. As described in the other thread, this capability has been demonstrated, and Autel plans to release this functionality soon in their next update.

 

[MrFixit]

Battery capacity is actually a variable

@DucRider ,
Given this fact, can you speculate as to how Honda may have come up with a fairly 'robust' way to track the 'Battery Capacity' of the Clarity?
Since this parameter feeds into their warranty coverage, it needs to be pretty good. It is also calculated live and in-situ while the vehicle is used during normal service (no specialized charge / discharge tests to derive it)...

 

[Landshark]

When you are comparing the LiIon to the lead acid are using nominal voltage vs fully charged voltage.

I think there’s a question in there somewhere.

I used the OEM specifications provided by the manufacturers of the battery banks that I own and what I believe we know about the Clarity battery. It was intended to be an example of how using aH’s as a measure of battery capacity could be misinterpreted, confusing or less straightforward than using kWh’s as a standard. Particularly for those not familiar with the laws of electricity.

It was not intended to start a discussion on the variables that impact the actual output of a battery.

 

[Landshark]

Given this fact, can you speculate as to how Honda may have come up with a fairly 'robust' way to track the 'Battery Capacity' of the Clarity?

I speculated previously in the middle of a rambling post, that tracking charging current over time would provide this information. Since the capacity test is intended to give current (I had to do it) data, it may refresh every 30 days or X number of charges.

Sorry for going out of turn.

 

[PHEVDave]

Although you could theoretically do this, there is a better way. Perhaps you haven't seen this thread.
This device is low cost in the scheme of things. Even if you were inclined to try and reverse-engineer the CAN traffic (far from trivial), it would be way easier to do it using the AP200 because you don't have to navigate around the dealer and 'hide' your CAN sniffing activity. As described in the other thread, this capability has been demonstrated, and Autel plans to release this functionality soon in their next update.

That would be great. And as soon as I hear that this feat has been accomplished I’ll probably buy an AP200.

 

[insightman]

That would be great. And as soon as I hear that this feat has been accomplished I’ll probably buy an AP200.

I dunno. I bought my AP200 ahead of the update, assuming that thousands of Clarity PHEV owners would drain the supply when the update is released. However, I'm turning a little blue as I continue holding my breath, waiting for the update. At least I'm not wearing out my AP200 while it languishes in the package.

 

[MrFixit]

I'm turning a little blue as I continue holding my breath

Patience is a virtue !

 

[Ohliuw]

So waiting for Aukey?

Found this paper on sniffing and reverse engineering the packets:

https://users.cecs.anu.edu.au/~sid.chau/papers/obd_EVSys16.pdf

 

[Ohliuw]

Any updates? For those in Canada, PrincessAuto is selling it for 99cad reg. But it goes on sale for 69.