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Battery question...

Discussion in 'Battery Discussion' started by Fr23shjive, Mar 2, 2012.

  1. Fr23shjive

    Fr23shjive Member

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    Just had a couple questions about Li-ion batteries.

    1. When a battery's cells degrade is it cause by individual cells "dying" or is degradation among all the cells equally?

    2. If it's individual cells that "die" then can you replace those with out replacing the entire battery?
     
  2. dhrivnak

    dhrivnak Active Member

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    I believe Tesla tries hard to keep the cells balanced. You can not replace cells but you can replace a sheet which is 1/11 of the pack.
     
  3. Dan5

    Dan5 Member

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    Degradation should be equal between all cells barring some 1-offs. One cell you will not really notice, maybe 50 cells, maybe 100 cells is when you may notice.

    Replacing individual cells could prove to be a pain and a waste of time- imagine having to test thousands of cells just to find that one bad cell, testing them would be a full time job
     
  4. Fr23shjive

    Fr23shjive Member

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    Oh ok, I was wondering if it'd be possible to replace dead cells instead of replacing the entire battery. Sounds like it wouldn't really save you money.
     
  5. dsm363

    dsm363 Roadster + Sig Model S

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    Tesla might be able to do this at a service since the Model S battery can easier be removed from the car but it's not something you could really do at home. They probably couldn't do individual cells but maybe the battery pack is in sections like the Roadster (not sure about this).
     
  6. surfingslovak

    surfingslovak Member

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    There might be more qualified forum members to answer this question, but my understanding from everything I've gathered is that the cells are closely matched and will age at approximately the same pace. It's likely that individual points of failure will develop over time, and these are best addressed by replacing whole modules, or subsections of the pack, not individual cells. It's up to the manufacturer and its OEMs to decide if and how they wanted to salvage these modules. While it's conceivable that they will refurbish them, especially if it can be done cheaply, but it's also plausible that they will simply sell them on the secondary market.
     
  7. mt2

    mt2 Member

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    I'm certainly not an expert. But reading this forum and Tesla blogs for as long as I have, I've learned two things. First, the pack is liquid cooled so that cells in the center of the pack don't age prematurely. And second, the pack goes through a cell balancing cycle while parked.
     
  8. William13

    William13 Member

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    Tesla engineers say the individual cells may fail with minimal effect. This is part of their special sauce, checking cells before instillation, isolating failures, and preventing degradation.
     
  9. dsm363

    dsm363 Roadster + Sig Model S

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    That's correct. I believe cell balancing happens at the end of a charge.
     

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