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Range charge ok as battery degradation sets in?

Discussion in 'Model S: Battery & Charging' started by FlasherZ, Aug 25, 2013.

  1. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Question for those of you who are battery experts...

    Once battery degradation starts setting in, is it ok to leave range mode set to on? Let's say your battery degrades to the point where it only achieves 238 miles, or 90%. At that point is it okay to just leave it on range mode permanently?

    I imagine the answer is likely "no" but maybe I'll be surprised.

    After 9 months and 11,000 miles my range charge reaches 260 miles and stops (5.0 calculation). Just curious about the time I'll reach 240. :)
     
  2. brianman

    brianman Burrito Founder

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    Numbers check. Assuming you mean rated miles, I would call 238 miles at 90% augmentation not degradation. Did you mean 93%?
     
  3. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I wasn't speaking of the charging slider today, but rather when a range charge starts resulting in a max charge of 238 miles (90% of original rated range-charge miles)...
     
  4. evme

    evme Member

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    Pretty sure the answer would still be no

    That said, the degradation curve pretty much shows that after the initial loss of around 400 cycles it begins to slow down in general.
     
  5. brianman

    brianman Burrito Founder

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    Let's see if I'm understanding you correctly...

    1. "max charge": I presume you mean Range (4.4) / Trip (4.5) charge so your vehicle at delivery would have started with typically 265 miles (though some have seen numbers in the 270+ range).
    2. battery degradation of 90% (nothing related to the charge slider)

    Is that what you meant?

    Sorry for the potential detour. It's been a long weekend.
     
  6. djp

    djp Roadster 2.0 VIN939

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    Answer is no. Keeping a degraded battery at high SOC is a good way to push it off a cliff and into a downward spiral of even faster degradation.
     
  7. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

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    Degradation affects the capacity.. If a 85 kw battery degrades to 80, then a 100% charge is now 80 kw, and still has the same effects as a 100% charge of any battery capacity. The problem is significant for small batteries in that the degraded capacity may force one to charge to 100% more often for daily needs, thus hastening even faster degradation. That is definitely an issue with the LEAF, probably unlikely with the 60kw battery, and close to impossible with the 85 battery. Imho
     
  8. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    #8 FlasherZ, Aug 26, 2013
    Last edited: Aug 26, 2013
    That's what I figured, just an odd thought that popped into my mind. Simplified version is if 100% SOC battery pack = 400V and 90% SOC battery pack = 360V, and degradation leaves the pack to only reach 360V in 100% mode, why not just leave charge to trip/range/100% so that it reaches that max? Over-simplifying I'm sure by far...

    - - - Updated - - -

    Correct. My car's max range/trip/100% charge at delivery went up to about 272 or so, but that was with the old pre-4.5 and pre-5.0 range calc changes too. It will now stop charging at 260 miles when on a 100%/trip/range charge, or 2% loss over 9 months. That said, there were some calculation changes noted in 4.5 and even some rumors about calc changes in 5.0.

    I think I've resolved this in my head, it would unnecessarily push those cells that weren't degraded quite yet.
     
  9. wycolo

    wycolo Active Member

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    High mileage Roadsters are already facing the choice: do I Range Charge daily to enable my normal commute (thereby killing battery life even faster) or spend money/effort so the car can get a charge somewhere during the day's commute.
    --
     
  10. bluetinc

    bluetinc Member

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    The pack voltage (SOC) will continue to be the same regardless of degradation. It is the amount of energy which it is holding that is reduced. For example when new a SOC = 100% and pack voltage of 398V equals 265 rated miles. After 10% degradation, a full range charge will have a SOC = 100% and a pack voltage of 398V and 238 rated miles. This drop needs to be seen by software which calibrates itself to account for the loss of capacity.

    Peter


     

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