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Thread: Tesla million mile battery

  1. #11
    Evolution is God's ID rogue06's Avatar
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    Quote Originally Posted by oxmixmudd View Post
    A few months back Elon Musk anounced that they had a technology that would allow a battery to last 1,000,000 miles. A study was released of that technology that shows that indeed, they have a battery technology that will only lose 10% of its capacity in 1,000,000 miles. That is quite amazing. The interesting thing is that they published sufficient details to allow others to apply the technologies to their own battery production. This has generated some speculation Tesla already has something even better.

    1,000,000 miles on a battery does a couple of things.

    1) it provides a market for used batteries. It they last nearly forever, just put them in another car if he first one dies
    2) it means fewer batteries need to be produced because replacements are not as likely to be needed.
    3) better for the environment - less used up batteries to dispose of.


    https://www.extremetech.com/extreme/...e-battery-tech


    Jim
    As they say timing is everything. About the time this story was released police in Fremont California had to abandon a chase because their tesla battery was running out of power.

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  2. #12
    radical strawberry
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    Quote Originally Posted by TheLurch View Post
    These are transition metal elements; the outer shell is not always the only one that matters. For example, the most common form of manganese in chemicals is Mn+4. But it can also exist in the +2 state.
    I worked with a gal in a visualization lab doing research on separating Fe+2 and Fe+3. Pretty pictures, but I never grokked the chemistry. Pretty pictures that needed a whole lot of processing. We'd both scored some Large Scale Computing grant money facilitated by the National Center for Supercomputing Applications.


    I had looked at the abstract when the paper was first released, and looked in a bit more detail in response to this. This is a pouch cell, which is very convenient for testing, but doesn't represent something that has all the components of a commercial battery, and may not perform as well when the same chemistry is placed in a form that can be manufactured at scale. I'm also somewhat concerned by the statement "Details of the cells used in this work will be given later, as will a full set of performance data."

    We also run up against the limits of my knowledge in the description of the charge/discharge experiments, as i can't read the experimental description and understand what % charge points they cycled between. Lithium batteries tend to have much higher durability when they aren't charged or discharged fully (so, cycling between, say, 20% and 90% will give much better results than cycling between 5% and 95%).

    So, in sum: potentially quite exciting, but i'd need to talk to someone who knows batteries better than i do before i'd get excited about it.
    Keep reading! The details you're asking for are in the legend to Figure 1:

    The data from this work for 100% DOD cycling was collected to an upper cutoff potential of 4.3 V. The data from Ecker et al., used 4.2 V as 100% state of charge. The purple and green data (this work) should be compared to the black data (Ecker et al.). Data for restricted range cycling (i.e. 25 - 75% SOC and 40 -60% SOC) for the cells in this work is not available but is expected to be far better than the data shown for 0 – 100% DOD cycling by analogy with the cells tested by Ecker et al.

    Figure 1.jpg

    The closest comparison is between the NMC532 from this paper cycling 0% to 100% (at 40ºC) and Ecker cycling 40% to 60% (at 35ºC). I don't understand the 1C and C/3 designations, but the fact they were doing full cycles at a higher temp, and beating partial cycles at a lower temp means they're beating the Ecker cells with both hands tied behind their back.

    Data for restricted range cycling (i.e. 25 - 75% SOC and 40 -60% SOC) for the cells in this work ... is expected to be far better ... by analogy.

    The focus is toward commercial EVs, cabs and long-haul trucks that will come in needing full cycles, and personal vehicles plugged in to a smart grid providing base power at home.

    Folks who've been following my personal adventures know I'm within a year of going (mostly) off grid on land in the Everglades, hence my deep interest here.

  3. #13
    radical strawberry
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    Quote Originally Posted by rogue06 View Post
    As they say timing is everything. About the time this story was released police in Fremont California had to abandon a chase because their tesla battery was running out of power.
    Nobody leaves links anymore.

    Cops Abandon High-Speed Chase When Their Tesla Battery Runs Down
    By Bill Howard on September 27, 2019 at 2:18 pm

    Don’t feed the sheriff’s horse tonight and Blaze won’t much feel like chasing cattle rustlers tomorrow. Don’t gas up the Ford Interceptor and you not make it much farther than Dunkin in the morning. Now the cops are learning: If you don’t charge your Tesla police car, the next shift won’t mount a very long high-speed pursuit. It happened this month in Fremont, California. The police department’s Tesla ran low on juice and the chase was called off after about eight miles. The Fremont PD said it was for reasons of public safety.

    Public safety, yeah, that's what we'll call it.

    The Fremont PD did note the car somehow hadn’t been plugged in to charge at the end of its previous shift.

  4. #14
    tWebber lee_merrill's Avatar
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    Quote Originally Posted by rogue06 View Post
    This reminds me of how not all that long ago aircraft manufacturers were insisting that planes could keep flying indefinitely as long as they received proper maintenance. Then you had a couple high profile crashes resulting from things like metal fatigue.
    Though Tesla has validated their drive train for a million miles! Which is also not indefinitely...

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  5. #15
    tWebber TheLurch's Avatar
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    Quote Originally Posted by Juvenal View Post
    Keep reading! The details you're asking for are in the legend to Figure 1.
    Right, but unless i've read that wrong, the percentages are defined relative to an output voltage (the voltage will change as the battery nears empty or full). What i don't understand is how to relate those voltage changes to how much additional charge can still be extracted from the battery at that point.

    But now that you highlight that graph, the red vs. blue lines does really drive home the relationship between battery performance and how much you stray from intermediate discharge states.

    Quote Originally Posted by Juvenal View Post
    I don't understand the 1C and C/3 designations, but the fact they were doing full cycles at a higher temp, and beating partial cycles at a lower temp means they're beating the Ecker cells with both hands tied behind their back.
    C is simply a measure of how fast you charge it. C/3 is a pretty slow charge; 1C is what would be considered a normal charging rate for a battery of this size. Batteries tend to perform better if you charge them more slowly, as the ions have more time to integrate into the electrode in an orderly way.
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  6. #16
    radical strawberry
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    Quote Originally Posted by TheLurch View Post
    Right, but unless i've read that wrong, the percentages are defined relative to an output voltage (the voltage will change as the battery nears empty or full). What i don't understand is how to relate those voltage changes to how much additional charge can still be extracted from the battery at that point.
    I really appreciate you taking the time with me. I not only don't understand the relationship between voltage changes and charge remaining, I'm not even sure who to ask. And more than that, when I was growing up, we believed in saying the pledge of allegiance, brushing your teeth after every meal, and 2.1V for a wet cell battery. I can see 4.2V from a pair of them in series, but why that, or 4.3V for that matter, would be part of the specs for these Li-ion batteries is a mystery.

    If there's a formula, that'd be bonus. I grok formulae just fine.

    But now that you highlight that graph, the red vs. blue lines does really drive home the relationship between battery performance and how much you stray from intermediate discharge states.
    Red, blue, and black, with the black being the authors' preferred comparison with their NMC532.

    C is simply a measure of how fast you charge it. C/3 is a pretty slow charge; 1C is what would be considered a normal charging rate for a battery of this size. Batteries tend to perform better if you charge them more slowly, as the ions have more time to integrate into the electrode in an orderly way.
    Okay, I really don't like this. Why would they choose to publish C/3 at 40ºC rather than 1C, like everything else, unless they did both and found they needed C/3 to beat the best of the Ecker et al. cells.

    Looks like cheating.

  7. #17
    tWebber Roy's Avatar
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    Quote Originally Posted by lee_merrill View Post
    Interesting indeed, now we just need a million-mile car to go with it. Though electric vehicles are substantially simpler than their gasoline-powered counterparts, so maybe a million-mile car would be possible?
    A million-mile car is not only already possible, it's happened - the current record holder being a Volvo in North America that's been used for a several hundred mile daily commute for decades and has clocked up over 3,200,000 miles.
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  8. #18
    Must...have...caffeine One Bad Pig's Avatar
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    Quote Originally Posted by Juvenal View Post
    Okay, I really don't like this. Why would they choose to publish C/3 at 40ºC rather than 1C, like everything else, unless they did both and found they needed C/3 to beat the best of the Ecker et al. cells.

    Looks like cheating.
    Yeah, it does. The Ecker data is all at 35ºC; one wonders why the new data wasn't obtained at that temperature for a direct comparison.
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  9. #19
    radical strawberry
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    Quote Originally Posted by One Bad Pig View Post
    Yeah, it does. The Ecker data is all at 35ºC; one wonders why the new data wasn't obtained at that temperature for a direct comparison.
    All the other data shows decreasing performance as temperature increases, so this bias is in favor of the Ecker cells.

    There's one more bias in the overcharge of 4.3V vs. 4.2V, but I don't know which way that leans.

  10. #20
    tWebber TheLurch's Avatar
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    Quote Originally Posted by Juvenal View Post
    All the other data shows decreasing performance as temperature increases, so this bias is in favor of the Ecker cells.

    There's one more bias in the overcharge of 4.3V vs. 4.2V, but I don't know which way that leans.
    I think you're going overboard in imputing bias here. It's perfectly reasonable (and generally important) to identify how two experiments differed in order to consider things like the degree to which they can be compared, or whether it counts as a reproduction, etc. But there are plenty of reasons for experiments to differ that don't involve someone trying to make their results look better than previously published stuff.

    Labs have limited time and resources. It could be that the lab was most interested in conditions that are different from those tested by other labs. or they don't have the same equipment available for testing, or they tried to do a number of experiments but the one that was a direct reproduction of previous results failed for some random reason. It could even be as simple as a grad student not knowing the literature and setting up the experiments that looked interesting to him. In this case, since we're talking long-duration battery testing, it's not an easy thing to go back and redo an experiment later if your realize you don't quite have the data you wanted.

    So, there's plenty of non-nefarious reasons the experiments don't precisely mimic what's in the literature. It's a reason to be cautious about interpreting the results of these experiments in comparison to others, but it's not a reason to assume the researchers arranged that intentionally.
    "Any sufficiently advanced stupidity is indistinguishable from trolling."

  11. Amen Teallaura amen'd this post.

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