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I'd like to see at least one other independent study which corroborates the finding in this paper that age related degradation is slightly less at 100% charge than 80%. Can anyone find any unrelated research drawing the same conclusion ? Otherwise it could be a case of picking one piece of evidence that happens to agree with a certain view point.

I've read quite a few battery research papers and also manufacturers cell datasheets over the last few years of EV ownership and this is literally the first one I've seen that came to this conclusion. Also, you have to wonder why a company like Tesla would make 80% charge the default and strongly recommend only to charge to 100% for long trips if it was actually less harmful to charge to 100%.

Because no other research that I've seen agrees with the claim in this paper I have to consider the possibility that there is an error in their methodology.
Good point. The beauty of a scientific paper is that they supply references that you can look up (there are 17 in this paper). These references will justify their methodology and experimental approach. Also, you have to consider what the experiment was trying to assess. This one was the effect of regenerative braking on battery degredation. The calendar degredation was not their primary goal, mearly a baseline to measure against.
 

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Hyundai Kona, Halfords bike
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Discussion Starter #42
Nobody under a certain age buys cars.
I'd agree, I doubt anyone under 17 buys a car. Even under 18, they't get their parents to buy it.

In reality, you probably won't have it long enough to notice the effects, assuming you swap cars every 2-3 years like the majority of folk.
I was thinking about this.

So if most ordinary folk sell their car after 2 - 3 years, who is left to be buying the 2 - 3 year old cars?
 

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Kia e-Niro MY20 64 kWh - Gravity Blue
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5% buffer based on capacity, or voltage. What are you basing your assertion that the car is sitting at 97% on (a fictional B U battery).Come on this is pub talk!
Based on the fact that gross capacity is ~67 kWh and net capacity is 64 kWh. Therefore the max charge rate is somewhere between 95% and 100% where 97% is a safe assumption since it is very probable there is a protection to not let the battery run to 0%.
 

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I was thinking about this.

So if most ordinary folk sell their car after 2 - 3 years, who is left to be buying the 2 - 3 year old cars?
The people who can't afford to buy a new car. :)
The Ioniq and the Kona are the first cars I have ever bought new (mainly because there were no 3 year old models available when I was buying). I always felt that cars depreciated SO much in the first 3 years that it was more cost effective to buy them after 3 years. And I usually keep them for over 5 years (or longer if I get a good one).
 

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Based on the fact that gross capacity is ~67 kWh and net capacity is 64 kWh. Therefore the max charge rate is somewhere between 95% and 100% where 97% is a safe assumption since it is very probable there is a protection to not let the battery run to 0%.
There will definitely be a low end buffer because if a lithium battery is fully discharged, it becomes and expensive lump of metals and organic electrolytes. :)
 

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why a company like Tesla would make 80% charge the default
It gets a bit tricksy here. Rapid charging to/at high SoC is harmful, but it's not the same problem as (eg) slow charging to high SoC and then leaving it like that for a long time.
 

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What is "0%" and "100%" are simply limits that battery manufacturer has set to guarantee that the battery will outlive its specified lifetime. The car manufacturer will then, just to be sure, set the BMS 0% slightly above the battery manufacturer spec, and likewise the 100% slightly below the battery specs 100%.

With these limits, the car manufacturer is confident that no matter how badly you charge your car, the battery will outlast the 160 000km/8 years warranty. If there would be any gotchas, they would have to state it in the manual - and the manual doesn't state "don't keep it charged at 100%". 8 years to 70% of capacity means MAX 3.75% of degrading per year by calendar aging alone. OTOH now matter how well you treat the battery, it's going to degrade 1-2% anyways per year. So, pulling out of my hat, A few weeks at the BMS 100% would not move the needle much from the 1-2% zone to 3-4% degrading zone.
 

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What is "0%" and "100%" are simply limits that battery manufacturer has set to guarantee that the battery will outlive its specified lifetime. The car manufacturer will then, just to be sure, set the BMS 0% slightly above the battery manufacturer spec, and likewise the 100% slightly below the battery specs 100%.

With these limits, the car manufacturer is confident that no matter how badly you charge your car, the battery will outlast the 160 000km/8 years warranty. If there would be any gotchas, they would have to state it in the manual - and the manual doesn't state "don't keep it charged at 100%". 8 years to 70% of capacity means MAX 3.75% of degrading per year by calendar aging alone. OTOH now matter how well you treat the battery, it's going to degrade 1-2% anyways per year. So, pulling out of my hat, A few weeks at the BMS 100% would not move the needle much from the 1-2% zone to 3-4% degrading zone.
Yes, and ignore Battery University.
 

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What is "0%" and "100%" are simply limits that battery manufacturer has set to guarantee that the battery will outlive its specified lifetime. The car manufacturer will then, just to be sure, set the BMS 0% slightly above the battery manufacturer spec, and likewise the 100% slightly below the battery specs 100%.

With these limits, the car manufacturer is confident that no matter how badly you charge your car, the battery will outlast the 160 000km/8 years warranty. If there would be any gotchas, they would have to state it in the manual - and the manual doesn't state "don't keep it charged at 100%". 8 years to 70% of capacity means MAX 3.75% of degrading per year by calendar aging alone. OTOH now matter how well you treat the battery, it's going to degrade 1-2% anyways per year. So, pulling out of my hat, A few weeks at the BMS 100% would not move the needle much from the 1-2% zone to 3-4% degrading zone.
What some of us are trying to say is that we'd rather keep the degradation as low as possible. It's fine if you're happy to accept the higher end of the manufacturer's tolerance. I, however, plan on keeping my EV for a long time. The difference between 2% and 4% degradation over 8 years is 30 miles [of] range in my MG5.
 

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What some of us are trying to say is that we'd rather keep the degradation as low as possible. It's fine if you're happy to accept the higher end of the manufacturer's tolerance. I, however, plan on keeping my EV for a long time. The difference between 2% and 4% degradation over 8 years is 30 miles if range in my MG5.
Made up numbers?
 

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So you are one of those people who criticize others for giving numbers yet your only argument is 'ignore battery university'. Content wise your contribution to this discussion so far has been negligible.
Not really. I've pointed out that temperature is the bigger factor, so several days at UK winter temperatures is equivalent to several years at summer Arizona temps...hopefully OP can sleep snugly now and ignore the BS from the misinformed.
 

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Not really. I've pointed out that temperature is the bigger factor, so several days at UK winter temperatures is equivalent to several years at summer Arizona temps...
That is indeed scientifically sound reasoning
 

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Not really. I've pointed out that temperature is the bigger factor, so several days at UK winter temperatures is equivalent to several years at summer Arizona temps.
Not sure where you are getting your made up numbers from, because they are actually not true. If you bother to read the scientific paper and look at the data, the biggest effect on degredation were temperatures of 40 degrees Celcius (double that of 10 degrees and 25 degrees). So the data shows the reverse of your argument. Several days at summer Arizona temperatures will be equivalnt to a couple of weeks at UK winter temperatures (not made up numbers). :)

"As expected, cell aging accelerates with tempera-ture: The capacity loss at 40°C, ranging between 2% and 6%, is almost twice as high as at 25°C. A further lowering of the temperature, however, does not decelerate aging considerably. At 10°C, there is still a capacity loss between 0.5% and 3%, depending on SoC. Fig. 6 also shows that cells stored in a discharged state below 20% SoC exhibit the least capacity fade. Storage levels between 20% and 50% SoC cause a medium degradation rate. The fastest ca-pacity fade occurs at a SoC interval between 60% and 90%. A fully charged cell, however, shows a somewhat slower capacity fade again."
 

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Not sure where you are getting your made up numbers from, because they are actually not true. If you bother to read the scientific paper and look at the data, the biggest effect on degredation were temperatures of 40 degrees Celcius (double that of 10 degrees and 25 degrees). So the data shows the reverse of your argument. Several days at summer Arizona temperatures will be equivalnt to a couple of weeks at UK winter temperatures (not made up numbers). :)

"As expected, cell aging accelerates with tempera-ture: The capacity loss at 40°C, ranging between 2% and 6%, is almost twice as high as at 25°C. A further lowering of the temperature, however, does not decelerate aging considerably. At 10°C, there is still a capacity loss between 0.5% and 3%, depending on SoC. Fig. 6 also shows that cells stored in a discharged state below 20% SoC exhibit the least capacity fade. Storage levels between 20% and 50% SoC cause a medium degradation rate. The fastest ca-pacity fade occurs at a SoC interval between 60% and 90%. A fully charged cell, however, shows a somewhat slower capacity fade again."
You are contradicting yourself: best to keep cells fully charged always and never use them at all😁
 

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Not really. I've pointed out that temperature is the bigger factor,
That may be true, but most us us have no control over the weather.
We do have control over charging and use of the car.

Yours is the same basic argument as "Don't bother with a healthy lifestyle - you could die in an accident tomorrow." You are welcome to that philosophy, but don't try and argue that it's right for everyone.
 

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What some of us are trying to say is that we'd rather keep the degradation as low as possible. It's fine if you're happy to accept the higher end of the manufacturer's tolerance. I, however, plan on keeping my EV for a long time. The difference between 2% and 4% degradation over 8 years is 30 miles if range in my MG5.
I agree. My point was more that storing a few weeks at 100% won't degrade your battery much unless you do that regularly.
 

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There must be a reason that the ID.3 has on-screen recommendation to charge to 80%. You can of course override this and select 90 or 100% if you wish.

It's also interesting that very few, if any, HV batteries in the Chevy Volt Mk1 (aka Ampera) have degraded to the stage where the driver can detect anything failing. This car keeps the battery between 20 & 85% of true capacity range, and there's one that's approaching 1/2 a million miles on the road, still on original battery. Yes it's a hybrid, but even when in petrol-only mode the battery still gets cycled with small 0.4 kWh charge/discharge cycles going on continuously. And yes, thanks to that very large buffer at both ends, it's possible that the BMS hides any degradation by eating into that margin a bit. But the fact remains that with this 2012 tech, it's possible to make a Li-on battery last a very long time indeed if you treat it very gently.

Arguably 2020 tech has better chemistry that may make this pussyfooting completely un-necessary, but you're not going to know this for another 8+ years, are you? It's clear also that EV mfrs vary as to how close they set their BMS max & min points to the battery's own true max & min limits. ID.3 gives you 58 kWh from 62 kWh, so that's using 93.5% of the absolute max amount, leaving only a rather modest buffer at each end. So the question is, have the mfrs pushed these limits too close to the absolute boundaries? Some reductions in the past to early Tesla Model S capacities, and some early EV battery fires suggest that this can happen.

All these batteries get a lot of testing by the mfrs. Many tests can be speeded-up, compared to real-life; e.g. if you sit on your car seat once per day, that's 3500 sit-downs in 10 years use. You can test that with an automated dummy doing 1 sit-down per minute, that's 1500 a day, bingo, test completed after just a few days, and you may have worn out the dummy's clothing before the seat! But you cannot speed up time itself, so tests that look for degradation-over-time by definition take that amount of time to do. All you can do to speed up this 8-year test is to run it for say 1 year, measure the wear & tear, and then extrapolate into the future. Whenever you do this there's a risk of something unexpected happening, rather like metal-fatigue hit the Mk1 Comet; after a couple of flights the airframe would have registered zero degradation, so you extrapolate & say "it's fine forever". Metal fatigue was not expected to affect the corners of the passenger windows, but it happened.

So it doesn't do any harm to charge as gently as possible, and it just-possibly might do some good.
 
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