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  • Sunking
    replied
    Originally posted by nebster View Post
    No thermal mgmt needed for Tesla packs at fractional-C rates.
    Cheese and Rice what a load of BS. Get a clue, EV's run and charge at fractional C-Rates. Anyone with any kind of math skills like a 5th grader would know that is just plain ignorance, or a blatant lie. Which is it? Are you ignorant or a liar?

    For the rest of you who have at least a 5th grade education, take note. Tesla vehicle mileage is 300 to 400 miles. If the batteries were discharged at 1C would require you to go 300 to 400 mph. 1C is the 1-hour charge/discharge rate. Now Jethro you made it to 6th grade and should smell a idiot or liar. Those mileage are calculated at 50 to 60 mph. OK Jethro how many hours does it take to 300 miles at 50 mph?

    Did you come up with 6 hours? Well Jethro that is C/6 fractional C-Rate. Most off-grid systems can and will discharge a lot faster than that up to 1C in some applications.

    Jethro's, for the charge side of Tesla batteries depends on what class of charger you have. Level 3 is the fastest and you will never use one at your house unless you have $100,000 for one and even then you are talking a C/4 charge rate or about the upper limit of off-grid solar. Level 1 is your common house 120 volt 20 amp circuit and takes 12 to 17 hours aka C/12 to C/17 which is much SLOWER than any off-grid solar. The most common Charger in a house is Level 2 and is the exact same circuit your electric dryers uses of 240 volts @ 30 amps produces a C/8 charge which is where most solar systems fall into.

    So if someone tries to tell you EV batteries do not need the same protection because Solar Systems run at fractional C=Rate, tar and feather that Snake Oil salesman and run him out of town.

    -- question removed -- Moderator.
    Last edited by Mike90250; 11-20-2018, 11:55 PM.

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  • Desert rat67
    replied
    Originally posted by Justin B. View Post
    I was poking around looking at different used/surplus batteries and came across listings for Tesla Model S battery modules, 24V, 250Ah. Since Li can be discharged a lot further than SLA/AGM would something like this be a good replacement for a 600 Ah AGM bank or could they be ran in parallel? Pricing was in the $1300 - $1400 neighborhood.
    Just google Tesla Powerwall

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  • Desert rat67
    replied
    Not only has it been done successfully, there are several YouTube videos on it.
    Now if you have the money, Tesla currently has modified the battery array for home use and it

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  • Glen Lalljie
    replied
    Can anyone help? Anyone using Kilovault batter?

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  • Glen Lalljie
    replied
    I am try to replace agm batteries with kilovault lithium 4 -12 volt but inverter would not work(off grid manga sine 4400/midnite solar charge controls/21 panels)
    alte store says these batteries are drop in.

    Leave a comment:


  • nebster
    replied
    Originally posted by bcroe View Post

    I am saying 500 cycles means little, until the energy transferred per cycle is defined. That could be in KWH, or
    miles traveled, or % depth of charge. Bruce Roe
    It's a good point: the thing we care about perhaps most of all is total energy flux. If we only get 1000 cycles when running from 75% to 25%, that would be unfortunate.

    However, the data suggest that the total energy flux increases substantially as we back away from the knees, as we use lower rates (and therefore less heating), and so on.

    Put another way, if we went solely by the datasheet values, and our Tesla got 250 Wh/mile while running the battery from 100 to 0 and back again, we should be able to drive 500 cycles * 75000 Wh / 250 Wh/mile = 150,000 miles and then see the battery at 70% SOH. But, from the data submitted, it looks like the packs are achieving more like 92% SOH at that point. Moreover, the degradation curve is flattening. Unless there is another phenomenon that starts to drive cell decay that we can't see yet, the numbers suggest a much longer lifetime.

    This is one of those rare moments where the manufacturer datasheet values seem to be very conservative. Or maybe it is one of those all-too-common moments where the datasheet tells us information that is not especially relevant.

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  • J.P.M.
    replied
    Originally posted by jflorey2 View Post
    I posted a source that confirms that. It comes from the webpage of Marteen Steinbuch, a professor at the Eindhoven University of Technology. Naturally the forum won't allow me to post the link to it, or the data - but you can Google if you like. He got his data from a survey of Dutch/Belgian Tesla owners, a second survey of owners from the Netherlands and a third survey of owners from the US.

    No skin off my nose if people believe or disbelieve it. I am always happy to get more data on something like this.
    Understood.

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  • NorthRick
    replied
    Originally posted by nebster View Post

    This is incorrect.

    The Panasonic 18650s are rated to ~70% of their original capacity after 500 full cycles: 100% to 0% SOC and back. Of course, lifespan increases dramatically if one elects a narrower charge regime. And lifespan increases if temperature is kept lower. And lifespan increases if cells are held at less than 100% SOC during periods of non-use. (And, by the way, 70% of nominal capacity is far from used up!)

    None of that is to say that cobalt chemistries are super safe or that everyone should just go wire some crashed packs into their house. But, setting thermodynamic risks aside for a moment, it is clear that NCA and NMC chemistries can be cost competitive in a wide range of use cases.
    That's the way I read the graphs on that datasheet too. Also, the rate of loss of capacity was diminishing with the number of cycles.

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  • jflorey2
    replied
    Originally posted by J.P.M. View Post
    Point is, it's all from one place - a source SK seems to think is questionable, maybe because it may be biased, cherry picked, reinterpreted or just plain B.S.
    I posted a source that confirms that. It comes from the webpage of Marteen Steinbuch, a professor at the Eindhoven University of Technology. Naturally the forum won't allow me to post the link to it, or the data - but you can Google if you like. He got his data from a survey of Dutch/Belgian Tesla owners, a second survey of owners from the Netherlands and a third survey of owners from the US.

    No skin off my nose if people believe or disbelieve it. I am always happy to get more data on something like this.

    Leave a comment:


  • bcroe
    replied
    Originally posted by nebster
    However, the papers do show that lifespan can be substantially greater than 500 cycles in the right environment.
    I am saying 500 cycles means little, until the energy transferred per cycle is defined. That could be in KWH, or
    miles traveled, or % depth of charge. Bruce Roe

    Leave a comment:


  • jflorey2
    replied
    Originally posted by Sunking View Post
    Nice try Jeff, but all conjecture and not one documented case. Is a Green Mafia Blog site the best you can do?
    Here's another one that shows a similar result:

    https://steinbuch.wordpress.com/2015...radation-data/


    Attached Files

    Leave a comment:


  • nebster
    replied
    Originally posted by J.P.M. View Post

    Whatever you say.
    It's not what I say, I'm just pointing folks to the real data.

    Point is, it's all from one place - a source SK seems to think is questionable, maybe because it may be biased, cherry picked, reinterpreted or just plain B.S. It can also be 100 % true and correct. Without peer review/vetting/verification there's no way to tell.

    Because something is written/printed says nothing of its accuracy or veracity.
    It's not all from one place: it's a bunch of individual owners, all of whom are geeky enough to no doubt be very interested in whether their pack is likely to perform to specification over time, submitting the data. There is a whole forum of people discussing the data. There are numerous other indicators of veracity, and there is little incentive for someone to fabricate or mislead (because Tesla owners want to know, right now, if their particular pack is not performing).

    But, aside from that example, there is also a growing body of other published scientific literature illustrating cell longevity over time. And, just because it has been written and published, also says nothing of its accuracy or veracity. However, the papers do show that lifespan can be substantially greater than 500 cycles in the right environment.

    And, on EV forums, there are folks with conservatively-managed packs now clocking seven or eight years of good performance.

    And, on boat forums, there are also folks with packs closing in on a decade of service.

    At some point, each reader has to make his or her own decision on all of these sources, of course. But to say there are "no documented cases" with performance well beyond what Sunking suggested is silly.

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  • J.P.M.
    replied
    Originally posted by nebster View Post

    His words literally say "not one documented case." There are hundreds of documented vehicle packs in that one worksheet.
    Whatever you say.

    Point is, it's all from one place - a source SK seems to think is questionable, maybe because it may be biased, cherry picked, reinterpreted or just plain B.S. It can also be 100 % true and correct. Without peer review/vetting/verification there's no way to tell.

    Because something is written/printed says nothing of its accuracy or veracity.




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  • nebster
    replied
    Originally posted by J.P.M. View Post

    Not doing his thinking for him, but I took SK's post not as that no data existed, but rather that he was questioning the validity of at least some if not a lot of the data.
    His words literally say "not one documented case." There are hundreds of documented vehicle packs in that one worksheet.

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by nebster View Post

    I was responding to the post by Sunking suggesting that there was no data on Tesla pack longevity.
    Not doing his thinking for him, but I took SK's post not as that no data existed, but rather that he was questioning the validity of at least some if not a lot of the data.

    Leave a comment:

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