Model S

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Model S Acceleration Slower as Battery Depletes...

edited November -1 in Model S
So, for a while now, whenever I supercharge my car at night, my 70D seems to accelerate smoother and faster--I thought it was just me, but I just heard from a reviewer on you-tube that the car does accelerate slower as your battery depletes.

At what battery charge level does this slower acceleration happen? And does the car tell you this somewhere on the dashboard?

No wonder when I took some friends for a spin, the car seemed to not thrust as fast as it did on random days. So much for showing off. I then had to tell them, "sorry, this is the slow car, I bought the slow car..."

Perhaps I might have been lower on the battery charge level at the time . . . or 1 - 2 extra passengers makes the extra difference in weight to hinder thrust power? They weren't particularly heavy people. 150lbs the most.
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Comments

  • edited July 2016
    My June 2013 p85 still charges fully to 258 miles of range after nearly 55k miles. I haven't noticed any slowing down.
  • edited July 2016
    Op is asking if at a lower state of charge if the power is reduced. Not if it has less power as the battery ages. The answer is yes it does have less power below some point but I do not know where that is. Others will have to chime in on that.
  • edited November -1
    Of course...
  • edited November -1
    yes you lose torque/acceleration gradually as you battery depletes.
  • edited November -1
    Yes. Search for all our 0-60 track addicts. They all want to arrive at the track with the highest SOC.
  • edited July 2016
    The battery also protects itself at low SOC, by limiting power.
  • edited November -1
    As NKYTA says, those of us who take our MS to the drag strip certainly see a decrease in performance as SOC decreases. But I'd be pretty surprised if it was anything you could notice by "seat of the pants" until you get down pretty low (at least below 30% SOC). With my 85D, I've run a 12.58 1/4-mile with about 88% SOC. Same night, last run was about 12.9 with SOC at about 58%. The car was displaying a warning sign on the power meter on the last couple runs right as I neared the end of the 1/4-mile, but trap speed was still right about 107-108MPH.

    It really didn't feel any different to run a 12.6 vs. a 12.9, so if you're flooring it and power seems reduced, you should check the power meter for a warning sign. That would indicate power limiting and that would have a noticeable impact. But between 30% and 100% SOC, I'd be surprised if you noticed any different in a launch at a stop light, all other factors being equal.
  • edited July 2016
    Thanks @mscott. Didn't JB Straubel mention a reduction sub 90% at some point? Can't be bothered to Google, MadBum might be on track for another Giants no-hitter...
  • edited November -1
    In my 85D I can notice/feel differences in acceleration with as little as a 10-15% change in the state of charge. 100% state of charge accelerations are noticeably different than 75% state of charge accelerations, especially in the 30-60 MPH range.

    If I remember correctly, there was a thread over on teslamotorsclub.com that showed that the 85D battery current maxes out at 1100 A. Of course, as the state of charge goes down, the battery terminal voltage goes down, resulting in a decrease in maximum KW available.
  • edited November -1
    And MadBum gave up a hit, but now it is dinner time.
  • edited November -1
    OP lol at telling people you bought the slow car. I was just out and I floored my 70D with less than 50 miles of range left and it still felt very fast to me. I like telling people I bought the slow one before I take them for a ride. Then I floor it from a stop and they go HOLY SH*T this is the slow one!?
  • edited November -1
    The opposite is true also, that is when you have a low battery regenerative braking is greater. This is not a huge difference, but in some instances it is noticeable.
  • edited July 2016
    It was much more likely due to the extra weight of your passengers vs your battery's charge state.
  • edited July 2016
    @NKYTA, I can't get to the track with 90% SOC, so I have no first-hand track data for the >90% case. But I've run enough races now to know that my time will decrease approximately 0.02 to 0.03 seconds between runs (usually about a 2% SOC decrease), at least down to about 60% SOC. (The lowest I've ever run my battery at the track is 58%, and that was a banner night--16 quarter-mile runs). If I extrapolate my best run (12.58s at 88%) to 100% using the above data, I would expect a 1/4-mile time of about 12.40. But I don't think the voltage drop is linear in the very high and low SOCs and I highly doubt I could get 12.40 from 100%. I suspect the best I'd be able to get is about 12.50, which, not coincidentally, is what Tesla claimed for the 85D, IIRC.

    @SomeJoe, I agree, there's a very noticeable loss of acceleration below 20% SOC. Somewhere around 10-15%, the car even starts to deliberately limit power draw. I was, however, surprised to see the power limiting warning at the end of 1/4-mile runs with the SOC in the 60s.
  • edited November -1
    My 85 gets best accelerations right after a charge. I think the best moment to demonstrate the best acceleration is after you unplug it. If you charge to 90-100% and you leve your car parked overnight you won't have great accelleration in the morning. If you charge right befor you leve for an hour or so then you're going to get the Pmax. That my 2 cent :-)
  • edited November -1
    a heat of the moment thing perhaps?
  • edited July 2016
    Temperature sweet spot I guess :-)
  • edited July 2016
    Here's a news flash: an ICE car is slower when full of gas than when it's almost empty.
  • It is basically a large battery operated toy. So it is no surprise that performance degrades with SOC.
  • edited July 2016
    Higher voltage and higher battery temperature (within limits) yields more power. Thus, a freshly charged/Supercharged battery will be most responsive.

    That's why the PD's have the Max Battery Power setting, which warms (or sometimes cools) the battery to the sweet spot temp.
  • edited July 2016
    Yes acceleration/torque is reduced as the SoC is reduced. The approximate percentage is ~60% when it becomes noticeable. I've tested both Dual Motor and Single Motor and its the same. So enjoy your peak performance from 100% - 85% starting to taper from 84%-65% but not terrible noticeable. Then your noticeable decrease is (~60%) - 30%. Then anything below 30% is the protective battery mode where your power is visibly limited on the power gauge.

    This is not an exact measure, but just using this a point of reference for the difference in the FEEL of speed/accel as your SoC is reduced, a P85D will perform as such:
    100% - 85% = P85D
    84% - 65% = 85D
    64% - 30% = 75D
    29% - 5% = 70/60
  • edited November -1
    jlewisthe3rd +100. I proved this to myself and my son when We took my new P85 to the Sacramento Drag strip 3-4 times back in 2013, Tesla claimed power didn't decrease until you got down to 30 miles
  • edited July 2016
    My car appeared to start charging at 300 volts (I still had almost 100 mile range) and when nearly fully charged it was charging at 346 volts. That implies a drop in battery voltage as the range decreases. A 10% drop in battery voltage would result in a drop in maximum power of 21% available from the battery. However acceleration is governed by torque AND traction control so if you are not seeing a decrease in acceleration it may be because the traction control is limiting the torque applied to the driven wheels. Different makes of tyres may therefore give different results.
  • edited November -1
    Sounds like a rock and a hard case.

    You want full battery setup that is "full" and a pre-cooled (the battery, not the car), and that all works best?

    I won't ever beat many MS in my Classic, but it is fun around town and on long road trips.
  • edited July 2016
    Apologies I should have said a 19% decrease in the maximum power available from the battery.
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