Li-ion battery health measurements by reading the Battery Pack Capacity signal

[KentuckyKen]

As I found in the docs shared by @Atkinson and posted previously, both our batteries are supposed to be tested per the 13 page Pre Delivery Inspection Sevice Bulletin 17-093 dated 1/25/18.

I went back to my dealer and had them measure my Li-ion Battery Pack Capacity signal. As you can see, at 6 months of ownership, it reads 54.3 Ah and 320 volts which is ~17.4 kW. I didn’t get a reading at delivery but supposedly ours is rated nominally at 55 Ah at 17 kW.
I hope those who have this metric from their PDI will share so we can know approximately what the value is at the start of ownership.

Assuming my battery started at 55 Ah (which I don’t know) and after 6 months lost 0.7 Ah (55-54.3) then it has lost 1.27%, extrapolated to ~2.5% or 1.4 Ah per year.
The PDI states the cut off for replacement under warranty is reduction to 36.6 Ah capacity. So then if the loss of capacity is linear (which I also don’t know), then at this rate it would take 13 years to reduce to 36.6 Ah ([55-36.6]/1.4).
Again that’s with a lot of assumptions; especially not having the starting Ahs.

At the current time and at 54.3 Ah, I am getting a consistent 62 to 64 EV range estimate with temps in the 80s to 90s and ac set to 72 to 74 and speeds under 60. I don’t run the battery down to 0 (2 bars) because my trips are local and I don’t want the ICE to run. However my EV range is pretty consistent with the odometer and is usually just 2-3 miles per charge optimistic.

So at 54.3 Ah, I’m beating the Mulroney sticker stats by a good bit:
EV range high high 50s to say 60 w ac vs 47 (but will have to average with lower winter range to come)(was high 60s w no ac)
3.9 to 4.3 miles/kW
132 to 146 MPGe vs 110
23.2 to 25.6 kW/100 miles vs 31

But all the above are a factor of driver and driving conditions. I need anyone who got a Battery Pack Capacity measurement with their PDI at purchase or a later one (with number of months owned) to share on this thread so I can try and figure out how this battery pack behaves and how well my dealer took care of it before I drove it off. If I’m reading this right, it looks like my battery is OK.

Thanks in advance and PS: Will the Clarity Brain Trust please check my math and assumptions and chime in with additional insights. I’m a bio guy; all this EE is getting over my head.

 

[Sandroad]

Interesting read-out. You've made three assumptions not listed; 1) that the battery pack capacity is independent of temperature and 2) that the measurement is reliable within 2% and 3) that time is the other axis instead of miles. If any is important (and I suspect they are), then your Clarity battery capacity may be higher or lower than you think, compared to OEM. So, a one-time measurement at 82F ambient may not be enough for creating any lines/curves on graph anyway I also don't think you can do inter-car comparisons, giving the driver variable. Bottom line: get your long-suffering dealer to check your Clarity's battery every year at 82F ambient and report back in 5 years with 5 points on your line of Ah vs miles. (Tongue in cheek of course ).

In reality, if enough folks get a battery pack capacity measurement and report back, it would be interesting collective data.

 

[Eddgie]

I have read a great deal on the degradation of the Tesla batteries and the capacity charts almost always show that there is an initial drop off of a few percent, which then starts to flatten into a much more gradual decline.

I suspect that this is probably true of the batteries used in the Clarity. There will be an initial drop down to 95% or 96% capacity (which is not going to show on the gauge because Honda is not stupid enough to let the gauge really show 100% capacity because the batteries are not really allowed to charge to 100% capacity) but after this initial drop, the capacity will stay in the high 90s for a few years.

The chart on this page shows how it goes with the Tesla, and I would expect the same for the Clarity. Initial drop will be quick and sharp, but only a tiny percentage of capacity, then the slope flattens and stretches out.

https://www.greencarreports.com/news/1110149_tesla-model-s-battery-life-what-the-data-show-so-far

 

[Neil]

I have been worried about a decline in my battery capacity within my first 8-9 months of ownership. I've been noticing a steady decline in range along my daily commute. I live in Southern CA so weather isn't a big factor.


I brought my car in for testing and my battery capacity is at 51.8Ah and my V1 voltage is 302V. That's a 6% decrease in Ah according to the figures in the original post here and 8% in kWh assuming a starting 17 kWh as stated by Honda. However my average driving range on battery has decreased by about 11% from the first 3 months of having the car to now. To me these figures are disturbing, but Honda said everything looks normal. I am planning on call them to ask what they consider "normal". I'm pretty annoyed, this seems like too much of a decline too fast.

 

[Steven B]

Screenshot provided by my dealer does not show the V1 voltage; Software Title bar says version 1.004.0064 and first two listings are 'Absolute Throttle Position Sensor' and 'Air Temperature Inside the Vehicle'. The screen indicates there are additional values farther down, so maybe in this software version the V1 voltage is on the second page. Reposting from another thread: As of 19 Apr 2019, Battery capacity measured 52.9Ah. Measurement at PDI not provided (probably not done). Current mileage was 18.5k. Rough guestimate of 12k on pure EV mode.

Assuming the battery capacity was at 55 Ah in Dec 2017 and knowing it is currently at 52.9 Ah, a linear projection would be that it would fall to the warranty replacement level (36.6 Ah) at the end of year 2029.

I don't baby this one nearly as well as @KentuckyKen does his. Most of my accelerations are normal and not as though I'm trying to hypermile; decelerations are more planned.

 

[AnthonyW]

Reposting from another thread:

After 13 months and 19k miles I am at 54.0ah. I’m really pleased considering the huge weather swings in Kansas City. We go from 100 degree highs for the month of August to 0 degree lows during February. For the record I took delivery of my car as soon it arrived from off the boat from Japan so I am sure that helped.


Sent from my iPhone using Inside EVs

 

[Neil]

The PDI states the cut off for replacement under warranty is reduction to 36.6 Ah capacity.

KentuckyKen, what is the PDI and where did you find that information? I have tried contacting the dealer and Honda directly about what is considered normal degradation and can not get a straight answer from them. I'm wondering too about what happens if it is on track to reach 36.6Ah quickly but isn't there yet - will they really not replace until it gets to that point?

 

[KentuckyKen]

The replacement under warranty appears to be the point at which it goes below 36.6 Ah before the warranty runs out in 8 years (10 in California). I don’t think it can be anticipated. You have to actually reach it. Also note that the Battery Capacity Test for this is past the part that dealers are to do pre delivery. I asked nicely and my service dept ran it for me probably because I told them it was supposed to be done and they didn’t know any better. Probably the only time dealer ignorance worked in my favor.

Since we don’t know what the exact chemistry or even manufacturer of the LI-ion cells are we can only speculate as to their longevity. However the fact that the same battery packs are warranted to 10 years in California and that we have an excellent liquid cooling system and BMS that doesn’t allow the battery pack to be fully charged or discharged make me optimistic. Add to that the fact that our max charge rate is a Level 2 supplying a mere 7.2 kW which is a C factor of around .4 (7.2/17 kW). Common wisdom says anything below a C of 1 is good for the battery’s longevity.

FWIW, a Tesla owner in my local EvolveKY group says he’s seeing less than 2% degradation per year with his Tesla Panasonic batteries. I have no idea if that will hold true for us as no one has had a Clarity more than 2 years yet.

Attached is the Clarity specific PDI with this information and a lot more.

 

[insightman]

I'm wondering too about what happens if it is on track to reach 36.6Ah quickly but isn't there yet - will they really not replace until it gets to that point?

It's too bad the Battery Pack Capacity signal cannot be read with an OBDII scanner. Because it takes a dealer's service department some time to perform the Battery Pack Capacity check, it would be awkward to be taking your Clarity in week-after-week to get the latest reading as you track the slow decline. If the Clarity PHEVs going to California (10-year warranty) are the same as the ones going to the other North American locations (8-year warranty), then it's likely Honda engineered the battery pack to last at least 10 years. Unlike the air-cooled battery pack in the Nissan Leaf, which has been known to deteriorate rapidly, the Clarity PHEV has a liquid-cooled (and, in Canada, warmed) battery pack, so it is much better protected from battery-killing heat.

 

[MarkClarity]

Since we don’t know what the exact chemistry or even manufacturer of the LI-ion cells are we can only speculate as to their longevity. .

I think the consensus is the the battery pack is the Blue Energy EHW5 or EHW5B model used in the Accord Hybrid and the Clarity Fuel Cell. See this Accord Hybrid teardown and the product info page with a list of Honda vehicles which use the pack.

 

[Pushmi-Pullyu]

Assuming my battery started at 55 Ah (which I don’t know) and after 6 months lost 0.7 Ah (55-54.3) then it has lost 1.27%, extrapolated to ~2.5% or 1.4 Ah per year.
The PDI states the cut off for replacement under warranty is reduction to 36.6 Ah capacity. So then if the loss of capacity is linear (which I also don’t know), then at this rate it would take 13 years to reduce to 36.6 Ah ([55-36.6]/1.4).

It's not linear -- at least not over the relatively short period you're talking about -- and it's much more closely linked to total distance than time.

Below is a graph of actual third-party reported battery capacity degradation data for the Tesla Model S. The graph shows that over the first ~30,000 miles of travel, the capacity loss is relatively steep at first, but rapidly flattens out over the course of that distance.

Caveat: Please note the scale at the left. The graph is distorted to exaggerate loss over time by cutting off the bottom 82% of the graph! An overwhelming majority of the data points show less than 10% degradation over ~300,000 kilometers (~186,000 miles), and the worst is ~16% loss.

Of course we can't expect every BEV to follow this same exact pattern, because different BEVs use different cell chemistries, and different battery packs handle their cells differently. But I would expect to see a similar flattening over time for capacity loss in other BEVs, since we see the same flattening of capacity loss, for long-term repeated cycling, in li-ion batteries in general. (The Leaf may be an exception for that; the amount of fade over distance varies a surprising amount from car to car. Lack of consistency in capacity loss is a big problem with the Leaf.)

 

[KentuckyKen]

I think the consensus is the the battery pack is the Blue Energy EHW5 or EHW5B model used in the Accord Hybrid and the Clarity Fuel Cell. See this Accord Hybrid teardown and the product info page with a list of Honda vehicles which use the pack.

Yes, I’ve seen those posts, but we still don’t have that in an official Honda doc that pertains specifically to the Clarity and the Blue Energy Link does not list the Clarity, so I’ll have to use the Mythbuster’s terminology and call it plausible but definitely not confirmed.

 

[MarkClarity]

I think the consensus is the the battery pack is the Blue Energy EHW5 or EHW5B model used in the Accord Hybrid and the Clarity Fuel Cell. See this Accord Hybrid teardown and the product info page with a list of Honda vehicles which use the pack.

The marklines.com automotive industry site (which has more current info than the Blue Energy web site) states that Blue Energy supplies the Clarity Fuel Cell, Electric and PHEV. (sign up for a free trial to follow this link, or google "clarity phev 27.3 Ah" to see the text from marklines.com in the search result)

The same site indicates that the PHEV is not due to a redesign until 2023.

 

[KentuckyKen]

@Pushmi-Pullyu, thanks for reposting the Tesla graph. It’s one more data point we can refer to. It tells me that if our batteries behave at a level anywhere remotely analogous to the Panasonic batteries, that we will be in good shape 10 years down the road. Looking at the graph it would seem that 10 years of driving 15,000 miles/yr only resulted in about an 8% range loss. So 8% of our 47 mile EPA Seaver’s range would be about 4 miles bringing our EPA range down to 43 miles. And 8% of 55 Ah reduces it to only ~ 50 Ah. Of course we have different batteries so the comparison is something of a crapshoot.

All the optimistic direct and indirect evidence we have on the batteries makes sense. Honda set a very low threshold of battery replacement at a whopping 33% loss of capacity at 8 years (10 in California) since I assume they don’t wont to go bankrupt or suffer the bad press Nissan got over batteries failing to hold up. So I don’t see the 33% warranty threshold as an indication of where our batteries will be in 10 years. Will we loose some range? Yes. Will it be terribly bad (for most of us)? No.

And if we just could find someone who tested Blue Energy Cell’s vs. Tesla Panasonic cells in accelerated charge/discharge test, we could get a much better idea of our Clarity's battery longevity.

 

[Mark W]

What automaker has been using the Blue Energy cells the longest on what cars?

 

[Pushmi-Pullyu]

Looking at the [Tesla Model S] graph it would seem that 10 years of driving 15,000 miles/yr only resulted in about an 8% range loss. So 8% of our 47 mile EPA Seaver’s range would be about 4 miles bringing our EPA range down to 43 miles. And 8% of 55 Ah reduces it to only ~ 50 Ah. Of course we have different batteries so the comparison is something of a crapshoot.

I wouldn't assume the Honda Clarity PHEV's battery pack will degrade, on average, only ~8% over the same period. A PHEV's pack is much smaller than a Model S85's (BEV) pack, so it gets cycled a lot more frequently. I think it's safe to say that the Clarity PHEV will likely experience, on average, significantly more battery capacity degradation than a Tesla car does.

But on the plus side, it's quite likely that Honda chose a battery chemistry that holds up better to repeated cycling over the long term. Tesla chose cells optimized for high energy content and to some extent high power; a PHEV manufacturer with competent engineering will choose cells optimized to stand up better to repeated cycling. I think Honda has shown it's quite competent in this area, despite some "angry bees" concerns.

KentuckyKen, my purpose in posting that Model S graph was to show that for li-ion batteries, the degradation is far steeper at first than it is later on; that you shouldn't extrapolate the capacity loss over the first several thousand miles, or even the first several tens of thousands of miles, to an expected 10- or 15-year lifespan of the car.

 

[Pushmi-Pullyu]

Interesting read-out. You've made three assumptions not listed; 1) that the battery pack capacity is independent of temperature...

It has been established that temperature has an effect on li-ion battery capacity. With higher temperature, capacity actually goes up; that's one of the reasons why it's so hard to accurately measure li-ion battery capacity.

But I have no idea how much that effects capacity. It would be better to test it at room temperature (72° F), but I have no idea how much difference there is at 82° F. Perhaps the difference is insignificant; perhaps it's not.

​

 

[KentuckyKen]

Good points. We’ll only know the final answer in 10 years. But with liquid cooling and what appears to be a very good BMS, I am optimistic.
You’re right that with a smaller battery, degradation and resulting range loss will be a bigger problem for us than the much longer range EVs with larger battery packs.
Time will tell, but the few Battery Capacity Signal tests shared are looking good in the short term.

 

[rodeknyt]

KentuckyKen, what is the PDI and where did you find that information? I have tried contacting the dealer and Honda directly about what is considered normal degradation and can not get a straight answer from them. I'm wondering too about what happens if it is on track to reach 36.6Ah quickly but isn't there yet - will they really not replace until it gets to that point?

Neil...look in the canvas folio that you got containing the owner's guide and other stuff when you took delivery. The (presumably) filled-out PDI booklet should be in there.

 

[Agzand]

It is true that a PHEV battery gets cycled more than a long range BEV battery, but on the other hand it is designed to maintain more capacity in charge/discharge cycle. Clarity gets full charge in about 12.5-13 hours on Level 1 at 11 amps. That is about 12.5/13 kWh, considering charging efficiency. So about 72% of the battery is used in each cycle. That is a lot less that what Tesla uses. With time probably they keep increasing this ratio, so a 15 year old battery could use for example 90% of the remaining capacity. I don't expect significant range drop in a typical life cycle of 10 years or so.