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3.0 Battery Longevity

Discussion in 'Roadster' started by bolosky, Feb 14, 2017.

  1. bolosky

    bolosky Member

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    I got my 3.0 upgrade in early October, so it's been about 4 months. In that time, I've put roughly 6K miles on the battery.

    When I first got it, I did a couple of range charges both to see what it was showing and also because I had to do a long drive (and then back). The best that I saw was 344 ideal miles with a CAC of 215.04.

    Since then, I hadn't needed to do a long drive, so I didn't range charge it. I noticed that the ideal miles in a standard mode charge declined somewhat, from maybe 225 to 217 or so. I looked for the first time in a long while, and the CAC had declined to 201.45, a little more than a 6% loss.

    I thought that maybe the problem was that the battery couldn't balance properly with the roughly 75% SOC in ideal mode, so I range charged it, let it sit plugged in for a long time to balance, topped off, and repeated a few times.

    The result of this is that the CAC improved to 202.24 (total capacity at full charge 74.36 kWh as opposed to 77.26 kWh new) and the standard range charge is back to 221. However, the best range mode charge I saw was 326, a full 18 miles less than when the battery was new (again, 4 months and 6K miles ago, so not very long ago).

    I figure that one of several things may be going on, rated from best to worst in their implications:
    1) The 3.0 battery has cells that have a quick initial dropoff in capacity, but then level out for a long while. I know that some of the Model S cells are like this (and I think in that case that Tesla just sells them as if they're at the plateau level). So, I should expect to stay near this capacity for a very long time, and the R80 is really more of an R74.
    2) There's something wrong with my particular battery, and Tesla will just replace it for me since it's a dud.
    3) The 3.0 batteries lose 30 ideal miles/10k of range (as opposed to ~3.7 in Tom Saxton's study for the 2.0 battery). So at 33K miles a 3.0 battery will have the same capacity as a new 2.0, and quickly descend after that. That is, the 3.0 batteries don't work and I spent $30K making my car be useless earlier than if I'd have kept the 2.0 battery.

    I really hope that Tesla didn't screw up in cell selection and it's not #3. Or that if it is that they'll suck it up and fix all of our quickly decaying batteries.

    Have any of the other 3.0 owners seen a decrease like this? How much mileage do you have on your new battery?
     
    • Informative x 3
  2. LargeHamCollider

    LargeHamCollider Battery cells != scalable

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    I don't have a roadster but I suspect that you got it right in your "option # 1."

    As a completely unhelpful aside, the roadster has 6,831 cells, the 100D has 8,256. Jason Hughes showed that the 100D has 102kWh total capacity, so if you stuck 100D cells in a Roadster pack it would have 82.7kWh total, probably 79 usable.
     
  3. spaceballs

    spaceballs Member

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    How balanced is your pack, go the logs?
     
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  4. wiztecy

    wiztecy Active Member

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    ^Agreed^

    If you haven't been driving and charging your battery pack to at least Std Mode, allowing the cells to balance your range will decrease and the CAC will drop. This is normal behavior. I've been taking the bus to work for close to a year, so haven't been driving my Roadster much. I keep the battery down at around 50-60% SOC and do a std. mode charge when I want to take it out for a fun jolt. When I'd drive and charge it regularly the Roadster would charge to 182 ideal miles and now it charges to 172. Also the CAC has dropped some. If I fully balance the pack I can bring it back to the 182 range again where the CAC will rise back up. Doesn't take much nor long for the pack to become out of balance. As spaceballs indicated, verify that your pack is balanced. If it is, then that is most likely true degradation.
     
  5. Stefan T

    Stefan T Member

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    It's winter for the moment and that lower the CAC
     
  6. slcasner

    slcasner Member

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    My 3.0 upgrade was done August 11, 2016, six months and 2433 miles ago. At that time the CAC was 214.30 and the max ideal miles I have recorded was 345 the next time I did a range mode charge on September 5. Two weeks ago I again did a range mode charge for the 289-mile drive from Sunnyvale down to Santa Barbara, this time recording 337 ideal miles. The CAC is now 204.32.

    I'll repeat part of what I said about that trip in the custom brake thread. Driving at 62 mph the ratio of real miles to ideal miles was 0.87 on the way down and 0.94 on the return trip. With the original battery, this trip required a 1-hour charging stop in Salinas and a 2-hour charging stop in San Luis Obispo. With the new battery it should be possible to go that distance with no charging stop, but to be conservative for the first trip, I planned a lunch stop in SLO where there is a good 240V 70A EVSE. After charging at home in range mode (337 ideal miles) I switched to standard mode for the drive, so I started out with 303 ideal miles. The distance to SLO is 195.9 miles but consumed 229 IM. The additional 93.4 miles to Santa Barbara consumed 102 IM, for a total of 331. That means I would have been down to fumes without the charge stop considering the 0.87 M/IM ratio. On future trips I could consider skipping the stop if time is more important than lunch and if the ratio is larger so that I have more like 130 IM remaining when I reach SLO.

    However, this is definitely shy of the claim that the 3.0 battery allows driving from the Bay Area to LA on one charge.
     
    • Informative x 4
  7. bolosky

    bolosky Member

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    I'm pretty sure that it's balanced. I drive it most days and standard charge, so it sits with a full standard charge for hours each day. I also range charged it, let it sit until it stopped balancing, topped off and repeated a couple of times. This is what got the CAC from 201 to 202.

    slcasner seems to have seen a comparable reduction in CAC with the same amount of time and less than half the mileage. In a way, that's good: it's consistent with scenario #1, where there's steep initial dropoff that then stops for a long time. My recollection from the curve I saw for the Model S cells was something like 1000 full cycles, which is > 250K miles for the 3.0 Roadster.

    Of course, these are different cells with different properties.

    Has anyone found a charge capacity vs. cycles graph for the LG cell in the Roadster? I looked around a little but didn't come up with anything.
     
  8. MileHighMotoring

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    What's the best/fastest way to balance the batteries and get the highest CAC?
     
  9. wiztecy

    wiztecy Active Member

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    Basically what bolosky said, to drive the car daily, do a full std. charge if you don't need a range mode charge, and allow the Roadster to sit for 1 hour after its charged. Keep that habit up over a few months and your pack will be and always will stay balanced. Its also the way to achieve the highest CAC if the pack was out of balance for some time or was sitting down at a low SOC for a few weeks.

    Only time I've seen the CAC do huge climbs is when the pack has been out of balance and sitting at a lower SOC, anything below the 82-84% balancing threshold. It gets more out of balance as the SOC drops. Then you'll see the CAC take on a mind of its own come Spring/Early summer and Fall/Early winter where it will bounce around, rising, falling, etc. typically due to temp changes. Nice when it climbs, you're like keep going baby! ...but when it falls you're like stop stop stop. Feels like the Price is Right and the Alp Mountain Climber Game as he's approaching the end of the mountain's edge!
     
    • Informative x 4
  10. gregd

    gregd Member

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    But with the 3.0 pack, a full Standard charge stops well short of the SOC that the original battery would start balancing at. I forget what has been quoted as the % SOC trigger for balancing, but I'm assuming they must have adjusted this for the 3.0 battery. Can this be verified? It would be unfortunate if 3.0 batteries only balanced on a Range (or nearly Range) charge.
     
  11. spaceballs

    spaceballs Member

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    I have the 3.0 upgrade too, it's been around 6 months now, starting was 209.61 Ah, today 209.03 Ah.
     
    • Informative x 1
  12. Botbldr45

    Botbldr45 Supporting Member

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    My car is going in for 3.0 upgrade on Monday in Scottsdale. Is there anything I could do to help with this discussion after I get new battery and over next few months to help understand the posted numbers?
     
  13. bolosky

    bolosky Member

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    How many miles have you put on the new battery? How often have you range charged it?
     
  14. bolosky

    bolosky Member

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    I did what I should have done in the first place and pulled the logs and looked at the CAC over time. It's more-or-less going down linearly, which is consistent with scenarios 2 and 3, not 1. Maybe some other folks with 3.0 batteries can do the same thing.

    The little bump at the end of the graph is where I range charged and balanced the battery, and the CAC hopped up by a tiny amount.
    CAC.jpg
     
  15. bolosky

    bolosky Member

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    For reference, here's the same graph for the lifetime of the car. The bump up around April 2011 is when I had a battery replacement, which took a long while to balance, so it went up gradually. Notice how much steeper the line is after the 3.0 upgrade than before. I am concerned.

    Lifetime CAC.jpg
     
  16. bolosky

    bolosky Member

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    Here's a better cropped version of the first graph.

    CAC.jpg
     
  17. MileHighMotoring

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    Geez. That means by 2027 it could be down as low as 198! Yipes. :p
     
  18. bolosky

    bolosky Member

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    The slope of the lines is -0.428 Ah/month for the old battery (measuring from the peak after the rebalance for the replacement battery in Oct '11 to the replacement) and -3.285 Ah/month for the 3.0 (measuring from installation in Oct '16 to now). If that trend continues, then the 3.0 battery will hit 157 Ah (a new original battery) in March of 2018, and will be worse than if I kept my 2.0 battery in Feb '19 at 123Ah.

    Needless to say, if this happens I will be most unhappy. It's still possible that the trend will level off. But honestly, if I knew it would be this bad I wouldn't have done the upgrade.

    I'm going to try range charging it every day for a week to see if it just needs more opportunity to balance. But I have the feeling that that's not it.

    Other folks with 3.0's, it would be great if you could post similar data for your batteries.
     
  19. spaceballs

    spaceballs Member

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    What is the voltage of your highest/lowest brick?
    Why not just start a normal charge, then stop it, and look at debug menu and look at balancing screen to see when it starts/stop balancing.
     
  20. bolosky

    bolosky Member

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    That's why I think it's not balance. The debug screen had stopped balancing at full range charge. Then I topped off and let it finish balancing again. I didn't look at the voltage, but it showed max 99% and min 98%.

    I have this sinking feeling that these are crap cells.
     

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