GRA
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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Sat Nov 25, 2017 11:55 am

RegGuheert wrote:
GRA wrote:There's certainly a reason to be concerned whether they will demonstrate the same longevity, when GM has increased the usable SoC from 65% to something over 75% (I've seen claims of 76-78%, and my own calcs come out in the same range).
I know of nothing that indicates that increasing the range of cycling from 65% of SOC to 75% or even more has any significant impact on durability, so I will assume you are making this up until you produce some evidence to indicate that there is a *real* concern here. <snip>
Reg, ask yourself "Why did GM limit the Gen 1 Volt's usable SoC to 65%, if they could have either used a smaller battery for the same AER and reduced the price (or made a greater profit), or else increased the AER for the same price?" Using a wider SoC range will increase degradation on any Li-ion battery - the only question is by how much. Maybe GM has determined that the difference between 65% and 76-78% isn't significant for their current batteries, or maybe they figure with the good rep they've established with the gen 1's pack they can afford to accept greater degradation (and more warranty claims) with the 2nd gen. in order to make the (initial) AER look better. That may well be the approach Nissan took with the 30kWh battery; given their track record it wouldn't surprise me. We know that GM is fully capable of penny-pinching for short -term profits even when it negatively affects them (or their customer's safety) long-term, so it's definitely a possibility. We simply don't know.

As for the Clarity, I worry about all PEVs' battery longevity until proven otherwise, unless they have a robust capacity warranty. Certain design features can make adequate longevity more likely, but only large amounts of real-world customer data will provide the necessary proof.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Sat Nov 25, 2017 12:13 pm

LeftieBiker wrote:
Based on what? There's already been an extended discussion of research, tests done, etc. for various SoCs/temps/chemistries, but unless they are done using the Volt 2's specific chemistry and other pack details in the specific conditions, the results are at best only general. To date we simply lack real-world (not accelerated lab) tests for the necessary period of time for the 2nd gen. Volt. When we get out to 4-5 years, we'll have a better idea.
Based on real world experience with various lithium batteries. Nissan seems to have set the benchmark low with the "Canary" pack for longevity, and they don't seem to have degraded any faster at 80%. The Volt already has a good track record for battery longevity, so there is no reason at all to think that the packs will start to degrade faster under what is still a very reasonable SOC range. Toyota has had great success with a similar charge range in the regular Prius, and NiMH packs are more temperamental than lithium packs over long periods.
The NiMh battery in the HEV Prius is a power not an energy battery, and unlike Li-ion, NiMh requires full cycling to maintain capacity. HEV batteries are designed for very different usage cycles, and shouldn't be compared to PHEV/BEV batteries. Even if they have similar basic chemistry, the details tend to be very different. Here's the abstract of an IEEE paper from 2002, discussing the 1st gen Insight' and Prius' pack management:
Abstract:
This study describes the results from the National Renewable Energy Laboratory's (NREL) chassis dynamometer testing of a 2000 model year Honda Insight and 2001 model year Toyota Prius. The tests were conducted for the purpose of evaluating the battery thermal performance, assessing the impact of air conditioning on fuel economy and emissions, and providing information for NREL's Advanced Vehicle Simulator (ADVISOR). A comparative study of the battery usage and thermal performance of the battery packs used in these two vehicles during chassis dynamometer testing is presented. Specially designed charge and discharge chassis dynamometer test cycles revealed that the Insight limited battery usage to 60% of rated capacity, while the Prius limited battery usage to 40% of the rated capacity. The Prius uses substantially more pack energy over a given driving cycle but at the same time maintains the pack within a tight target state of charge (SOC) of 54% to 56%. The Insight does not appear to force the battery to a specific target SOC. The Prius battery contributes a higher percentage of the power needed for propulsion. The study also found that while both vehicles have adequate battery thermal management system for mild driving conditions, the Prius thermal management is more robust, and the Insight thermal management limits pack performance in certain conditions.
http://ieeexplore.ieee.org/document/986 ... n=abstract

As knowledge has been gained, they may have been able to use more of the SoC range in subsequent HEV Prius generations, but I don't have anything to hand that shows that. INL's test of the 4.4kWh battery in the 2013 PiP showed that it used a max. of 2.5kW (under charge, 2.9 kWh from the wall, of which 2.6kWh went into the battery), or 57% to 59% SoC range. Note that the PiP's Li-ion battery falls in between a power and energy battery: https://energy.gov/sites/prod/files/201 ... usphev.pdf
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

GRA
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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Sat Nov 25, 2017 1:46 pm

Apropos of usable SoC:
Usable Energy: Key to Determining the True Cost
of Advanced Lithium Ion Battery Systems for Electric Vehicles
http://www.a123systems.com/Collateral/D ... epaper.pdf
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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RegGuheert
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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Sat Nov 25, 2017 2:29 pm

GRA wrote:Reg, ask yourself "Why did GM limit the Gen 1 Volt's usable SoC to 65%, if they could have either used a smaller battery for the same AER and reduced the price (or made a greater profit), or else increased the AER for the same price?"
That's an easy one: They were being conservative. The other part of the answer is that GM used cycling tests to determine the life of their batteries while completely ignoring the effects of calendar losses. At the end of the day, I have to conclude that allowing the battery to discharge to 10% SOC instead of 20% SOC likely results in little to no NET change in capacity loss because while cycling losses may increase, calendar losses should be reduced at the lower SOCs.
GRA wrote:As for the Clarity, I worry about all PEVs' battery longevity until proven otherwise, unless they have a robust capacity warranty. Certain design features can make adequate longevity more likely, but only large amounts of real-world customer data will provide the necessary proof.
The Chevy Volt has proven battery durability. The time to worry about that is past. Volt Gen 2 has been out for a couple of years and the batteries are doing great. Compare the Volt's performance with the reports coming in on the 30-kWh LEAF.
RegGuheert
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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Sun Nov 26, 2017 4:07 pm

In an earlier post I wrote:
The NiMh battery in the HEV Prius is a power not an energy battery, and unlike Li-ion, NiMh requires full cycling to maintain capacity.
For some reason while I was writing NiMh I was thinking (sintered plate) NiCd. NiMh has no memory effect (nor does pocket plate NiCd). It would be idiotic of Toyota or Honda to limit the usable SoC range to 40 or 60% if NiMh was subject to memory effect. Apologies for the mis-statement. The rest is correct.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Sun Nov 26, 2017 4:34 pm

RegGuheert wrote:
GRA wrote:Reg, ask yourself "Why did GM limit the Gen 1 Volt's usable SoC to 65%, if they could have either used a smaller battery for the same AER and reduced the price (or made a greater profit), or else increased the AER for the same price?"
That's an easy one: They were being conservative. The other part of the answer is that GM used cycling tests to determine the life of their batteries while completely ignoring the effects of calendar losses. At the end of the day, I have to conclude that allowing the battery to discharge to 10% SOC instead of 20% SOC likely results in little to no NET change in capacity loss because while cycling losses may increase, calendar losses should be reduced at the lower SOCs.
GRA wrote:As for the Clarity, I worry about all PEVs' battery longevity until proven otherwise, unless they have a robust capacity warranty. Certain design features can make adequate longevity more likely, but only large amounts of real-world customer data will provide the necessary proof.
The Chevy Volt has proven battery durability. The time to worry about that is past. Volt Gen 2 has been out for a couple of years and the batteries are doing great. Compare the Volt's performance with the reports coming in on the 30-kWh LEAF.
Yes, GM was being conservative with the 1st gen Volt , as every company should have been IMO, but that doesn't answer the question of why they felt that was necessary or desirable, if using an extra 13% isn't an issue. The 1st gen Volt has proven to have good battery longevity, although they have certainly degraded. Here's a post from GM-Volt.com describing INL's end of test results on four 2013 Volts:
Idaho National Laboratory's long-term battery pack testing of four 2013 Chevy Volts has reached end-of-test with the results linked in .pdf format above.

At quick glance, seems the worst performer was VIN #3491 which experienced @10% loss of Measured
Average Energy Capacity (kWh) dropping from a baseline of 16.7 kWh down to 15.0 kWh after 137,741 miles while the best performing, VIN #1078, only lost @8% (16.6 kWh baseline down to 15.2 kWh after logging 121,434 miles)

Going by this last measured data point for the worst Volt performer VIN #3491,

At 137,741 miles 16.7 kWh - 15.0 kWh = 1.7 kWh loss / 16.7 kWh = @10% total capacity loss

@10% / 137,741 miles = .0000726 capacity loss per mile

Following this established metric, we could roughly calculate our Volts should experience 25% capacity loss occuring at 25 / .0000726 = @350k miles and would this mean it is possible the battery pack in our Gen1 Volts will only be able to get 50% or half their original range clear out at an amazing @650k miles 50 / .0000726 = 688,705 miles baring no major battery pack failure!?
You can find the whole thread here: http://gm-volt.com/forum/showthread.php ... adation-No
but they are only talking about the 1st gen. cars. I've been unable to find a thread looking at 2nd gen. Volt packs with anything like that detail; I suspect they're still too new.

What has not been proved as of yet is how much if any additional degradation may be happening with the 2nd gen batteries, which are being worked harder.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Sun Nov 26, 2017 7:37 pm

GRA wrote:At 137,741 miles 16.7 kWh - 15.0 kWh = 1.7 kWh loss / 16.7 kWh = @10% total capacity loss

@10% / 137,741 miles = .0000726 capacity loss per mile
Why per mile, and not per EV mile? Most miles were "charge sustaining", or the gasoline engine was just keeping the battery pack cool while hauling it around.

EV miles = 15,637

https://avt.inl.gov/sites/default/files ... 91PHEV.pdf

That would be 25% loss at 39k EV miles, not quite so exciting. Probably should include some of the "mixed mode" miles, even though most of the energy for these came from gasoline. And the total of miles isn't at the end of the test, so would need to adjust as well, or ideally get the end of test totals of types of miles. So should adjust for all of that. Knock yourself out.
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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Mon Nov 27, 2017 4:02 pm

WetEV wrote:
GRA wrote:At 137,741 miles 16.7 kWh - 15.0 kWh = 1.7 kWh loss / 16.7 kWh = @10% total capacity loss

@10% / 137,741 miles = .0000726 capacity loss per mile
Why per mile, and not per EV mile? Most miles were "charge sustaining", or the gasoline engine was just keeping the battery pack cool while hauling it around.

EV miles = 15,637

https://avt.inl.gov/sites/default/files ... 91PHEV.pdf

That would be 25% loss at 39k EV miles, not quite so exciting. Probably should include some of the "mixed mode" miles, even though most of the energy for these came from gasoline. And the total of miles isn't at the end of the test, so would need to adjust as well, or ideally get the end of test totals of types of miles. So should adjust for all of that. Knock yourself out.
No need, just confirms my point.
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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Mon Nov 27, 2017 4:42 pm

GRA wrote:No need, just confirms my point.
This confirms my point: Zero Battery Degradation Replacements Giving Chevy Volts an Edge

That article was written at about the same time as the link you provided. Zero. None. Nada. Simply put, Chevy provided a 150,000 degradation warranty to many of their customers and had NO claims in the first four years on the road.

Again, the Honda Clarity battery system is the one to worry about since Honda is a company with a history of not standing behind their batteries that wear out. Both the original and the new Chevy Volt have stellar battery-degradation records.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
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Re: Official Honda Clarity FCEV/BEV/PHEV thread

Mon Nov 27, 2017 5:07 pm

RegGuheert wrote:
GRA wrote:No need, just confirms my point.
This confirms my point: Zero Battery Degradation Replacements Giving Chevy Volts an Edge

That article was written at about the same time as the link you provided. Zero. None. Nada. Simply put, Chevy provided a 150,000 degradation warranty to many of their customers and had NO claims in the first four years on the road.

Again, the Honda Clarity battery system is the one to worry about since Honda is a company with a history of not standing behind their batteries that wear out. Both the original and the new Chevy Volt have stellar battery-degradation records.
Reg, I believe I was the person who posted that story back when it first came out. :D What it tells us is that owing to GM limiting the usable SoC range to ca. 65% along with an active TMS the 1st Gen. Volt's degradation has been relatively good. Of course, the fact that GM had to certify and warranty the Volt's emission control system, which included the battery, for 150k miles to get CARB certification as a TZEV undoubtedly played a part - the 2011 Volt didn't have that certification because GM didn't have time to do it before the car was introduced.

None of this tells us what's going to happen with the 2nd gen. battery, which uses a greater SoC range of 76-78% of total capacity (GM says 14 kWh/18.4kWh, or 76%. See GM's comparison here: https://media.gm.com/content/dam/Media/ ... ATTERY.pdf Some sources have claimed they've seen up to 14.4kWh usable, or 78%), which is known to increase the rate of degradation - else, there would have been no reason for GM to limit the first gen. pack to 65%. As to Honda, as I've already said several times, absent any track record (based on the same tech and large numbers of vehicles), no one should count on longevity beyond the strength of the warranty. There were so few Accord PHEVs sold that we have almost no info about their packs, and the numbers probably aren't statistically significant in any case. One thing I was not aware of until reading the CARB T.A.R. I started a thread about is that Honda used the same cells for the Accord PHEV as they did the Fit EV. Only they and Mitsubishi (with the Outlander/iMiEV) have done this - everyone else uses different cells for BEVs and PHEVs. See pg. 20 here: https://www.arb.ca.gov/msprog/acc/mtr/appendix_c.pdf
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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