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D owners: When does current limiting occur?

Discussion in 'Model S' started by apacheguy, Mar 7, 2015.

  1. apacheguy

    apacheguy Sig 255, VIN 320

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    On my S, I start seeing the dashed yellow line appear on my power meter around ~50% SOC (when floored). Just curious where D owners start seeing this limitation and how much it affects acceleration. For instance, my S85 limits to ~285 kW at 50% SOC. I assume this is a pack imposed limitation. This would represent a severe restriction for D owners I would imagine.
     
  2. 3s-a-charm

    3s-a-charm Active Member

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    Never seen this? Never heard about it either?
     
  3. apacheguy

    apacheguy Sig 255, VIN 320

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    Then you've never been down at low enough SOC. The fact is performance degrades as the battery depletes its energy stores. You should start seeing it limit below 50% and most certainly at 20%. I'm just curious how much it limits.
     
  4. LetsGoFast

    LetsGoFast Active Member

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    I have only seen it when nearer to 20%. I'm pretty sure it doesn't happen at 40%, because I hit 40% pretty often. If no one else reports back sooner, I have a trip planned for Wednesday where I'll get below 20% again.
     
  5. breser

    breser AutoPilot Nostradamus

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    Can't say I've seen it in my 85D but it hasn't been very low on charge yet.
     
  6. apacheguy

    apacheguy Sig 255, VIN 320

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    Huh, so I wonder why my pack limits at 50%? Unless the D models have some improved conditioning system that allows greater current draw from the same 85 kWh battery at lower SOC. BTW, sometimes the dashed line only appears when you floor the accelerator.
     
  7. NielsChr

    NielsChr Member

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    Could it be temperature related. ?

    it might be that your battery is warmed up after driving X miles (aprox 50% SOC)
    Others might never see this battery temperature due to lower outside temperature.

    e.g I did never see this in my P85 - but I live in denmark where temperature rearly goes above 20 deg celsius, in fact I did offen see the yellow dot when starting the car due to low temperature (I guess you never see this in So Cal)
     
  8. Andyw2100

    Andyw2100 Well-Known Member

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    The power available can be limited for either reason--low battery or cold battery.

    If the power is being limited because the battery is cold, regen will also be limited.

    I have seen power limited in my P85D due to the battery being low, but it certainly has to be quite a bit lower than 50%. I think it might be somewhat higher than 20%, but probably not much. If I had to guess, I'd say the limiting line shows up at no higher than 30%, but before it gets down to 20%.
     
  9. dennis

    dennis P85D

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    I saw similar behavior in my P85+ with an 'A' battery (i.e. power limiting begins when SOC drops to 20%-30%). I will be on the lookout for when this happens in my P85D.
     
  10. apacheguy

    apacheguy Sig 255, VIN 320

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    As noted before, sometimes the only way to tell is to floor the accelerator. Meaning it is not a static limiter and disappears when power falls below a certain threshold. I suspect that it does affect D owners unless Tesla did something very different with the pack design.

    How about asking the question this way: Charge your PD up to 90% or greater and do road test while logging stream data from the REST API. You can use VT for this. Repeat at ~50% and measure the fall off in peak power output.
     
  11. Andyw2100

    Andyw2100 Well-Known Member

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    I can't use VT. I'm apparently on the new servers. I'm hoping Joe releases the version currently in beta, (and available as source code to those who know how to build it from there, since I don't.)
     
  12. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    I only have seen it when well below 20%; I don't remember the exact State of Charge where power limiting occurs, but probably closer to the 8% "red line" with a warm battery. You can get power limiting at 100% SoC with a very cold battery.
     
  13. mspohr

    mspohr Active Member

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    I've only seen the yellow dashed lines (both power and regen) when the battery is cold on my 85D. No relation to state of charge. As soon as the battery warms up, the lines go away.
     
  14. dirkhh

    dirkhh Middle-aged Member

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    OFF TOPIC

    Am I the only one who reads the thread title as "Downers" and can now no longer think of himself as a "D" owner?
     
  15. wraithnot

    wraithnot Model S VIN #5785

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    During normal driving I only see the power limiter at really low states of charge (10-15%). However, at freeway speeds if I floor it and the cars stays at full power for a second or two, then I sometimes see the yellow limiter line (I have a long uphill freeway on-ramp on my commute home and I saw this behavior on my original "B" battery pack and my replacement pack). I think this is the behavior apacheguy is referring to.

    I've never seen this at really high states of charge (e.g. 90%), but I have seen it happen as high as 80% SOC. I started to log data to figure out the exact state of charge where the limiter starts to appear, but it was really inconsistent and then I realized there was a temperature component as well (and it didn't have to be below freezing- even an ambient temperature of 50F was enough to make a noticeable difference). Since I don't have access to the actual battery pack temperature, I kind of gave up trying to figure out exactly what the parameters are for this current limiting. But I'd be interested to hear if anyone else has good data on this. And if this is something that only happens to cars with older battery packs.
     
  16. Eseell

    Eseell Member

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    Yesterday was the first time I had my 85D down to 40% SOC, but I didn't see the dashed line indicating limited power.
     
  17. breser

    breser AutoPilot Nostradamus

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    Looking back at the logs I had my car down to around 25% on the trip from Ellensburg to Ritzville on Saturday. Never saw the line. I agree with wraithnot that there's more to it than just SOC though. I don't think I really stepped on it at that low of State of Charge on Saturday.
     
  18. ThirdMartini

    ThirdMartini Member

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    I just did the foot to the floor from a light test 2x on my way home with 60Mi rated range left ( so 25-30% charge? ) No dashed line showed up. Butt-dyno felt like the car was taking off like when it was on full. ( I know totally scientific right? ) The only time i've ever seen that line popup was in very cold temp. ( But I've not had the battery down to anywhere near 20% yet )

    So either I'm not being limited when over 25% charge.. or the line does not show up on the display and my butt-dyno is lying to me.
     
  19. Doug_G

    Doug_G Lead Moderator

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    I've never seen a power limit until under 20% SOC, except of course in cold temperatures.
     
  20. mspohr

    mspohr Active Member

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    Real world report from my 85D.
    Today I drove up to Mt. Rose (9000 ft) to do some backcountry skiing. On the way up with 60 miles range the yellow line came on at a position just below the max of 320kW. This is a steep road but I was probably only using 160 kW. It stayed on until the top (44 miles range) and was on when I started back down the hill. It went away when the regen had charged to 50 miles and stayed off until the bottom. It came on briefly during a short uphill with 49 miles range. I then went over another pass (7500 ft) and it came on near the top (using 100-120 kW) but went off as soon as I let up on the throttle at the top of the pass.
    So, it seems that the limiting is dependent on how much you are currently using as well as the charge state of the battery.
    It's probably a complex algorithm and we are only looking at parts of it. We are the blind men and it is the elephant.
     

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