Tesla Model S Battery Degradation

Discussion in 'General' started by Carcus, Apr 4, 2017.

  1. Carcus

    Carcus Well-Known Member

    ahhhh, .. the peanut gallery :rolleyes:

    / perhaps those in the peanut gallery would like to step on stage and inform us all about an "adaptive internal resistance fast-charging algorithm" ---- I'm listening.
    Last edited: Mar 14, 2020
  2. S Keith

    S Keith Well-Known Member

    See #3 in my prior post. They're not charging as fast, and as the performance deteriorates, they're charging progressively slower.
  3. Carcus

    Carcus Well-Known Member

    I don't see the words "internal resistance" in any of your prior posts.
  4. Carcus

    Carcus Well-Known Member

    So I admittedly don't know a lot about battery charging, ... but I'll stumble out with some ideas/thoughts:

    Superchargers (at this point) still work on a the 'old' CC/CV principle but with some adjustment.
    Superchargers do not pulse -- I think the adaptive internal resistance fast charging mentioned in the post above would involve a form of pulse charging (but I do not know that)
    During charging, it is possible to measure pack internal resistance -- but you would really want to know the condition of each individual cell.
    Assumption -- Tesla battery packs are not wired to measure cell internal resistance directly.
    I think -- Tesla could get an 'indirect' idea of what individual cell internal resistance is by comparing voltage drops under load (cell vs. cell)
    (as I posted earlier) Tesla 'may' be hunting for high internal resistance cells when owners are reporting of a lot of pump clicking on and off while the car is plugged in and at rest (i.e. in the garage)
    -- Tesla may be changing the CC/CV charging algorithms and capping voltage on cars that show a high number of cells with high internal resistance (i.e. these would be cells with dendrites that are at risk of failing catastrophically)

    /some of this may be inaccurate or lack understanding -- all of it is speculation
    // just trying to figure out where the Tech is at currently
    Last edited: Mar 16, 2020
  5. Carcus

    Carcus Well-Known Member

    It's interesting now that [safe --- safer than NCA?] Lithium Iron Phosphate is gaining so much momentum. Tesla is reportedly going to purchase from CATL for their Chinese cars, .. and now BYD says they've got a new Lithium Iron Phosphate "Blade" battery ready to go.

    BYD's New Blade Battery Set to Redefine EV Safety Standards
    "SHENZHEN, China, March 29, 2020 /PRNewswire/ -- Today, BYD officially announced the launch of the Blade Battery, a development set to mitigate concerns about battery safety in electric vehicles.

    At an online launch event themed "The Blade Battery – Unsheathed to Safeguard the World", Wang Chuanfu, BYD Chairman and President, said that the Blade Battery reflects BYD's determination to resolve issues in battery safety while also redefining safety standards for the entire industry."
  6. Carcus

    Carcus Well-Known Member

    Questions I have for Tesla:

    - Is this the beginning of the end of 18650 and 2170 NCA cylindrical cells?
    - What is the supercharging capability of the Prismatic Lithium Iron Phosphate cells to go in the Chinese model 3s? Will these cars be more 'city car' oriented?
  7. S Keith

    S Keith Well-Known Member

    Not even close.
    Slightly lower than LiPo on a "C" basis, but lower capacity packs will charge in a comparable amount of time with shorter range.
    Due to their notably shorter range, most likely.

    The whole article is about safety vs. range. LiFePO4 cells are heavy and take up a lot of space and thus have shorter range. LiFePO4 also has a shorter life in an EV application. Yes, they can have many thousands of cycles; however, they don't benefit from "short" cycles like LiPo does. With LiPo, if you reduce your DoD to 40-60% of the pack capacity, you can have orders of magnitude longer cycle life. Not so with LiFePO4.

    In my personal experience with CALB made LiFePO4 cells, while they are VERY safe (they will not burn like LiPo), their lifespan is poor compared to LiPo.

    If you want range with a lower but still acceptable safety, LiPo
    If you want safety at the expense of range, LiFePO4

    And while LiPo is "less safe" aggressive battery management and monitoring minimize the risk. It's also a very mature and optimized technology where safety is no longer a serious concern given standard management practices.

    It's always helpful to remember that we have 10s of millions of vehicles on the road filled with flammable liquid with over 50,000 fires per year (https://www.usfa.fema.gov/downloads/pdf/statistics/v19i2.pdf).
  8. Trollbait

    Trollbait Well-Known Member

    The CATL cells are only going into the short range Chinese model. China has be using iron phosphate for years in buses, but buses have plenty of space for batteries. The lower energy density of the CATL pack means it will take up the space of the long range LiPo pack.

    If Tesla starts making LiFePO4 themselves, it will be for Powerwalls, not cars.

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