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The effect of Performance mode on battery life

Discussion in 'Roadster: Technical' started by raymond, Aug 26, 2010.

  1. scott451

    scott451 KWH-PWR#1349Sprt,S Sig#96

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    #21 scott451, Jun 27, 2011
    Last edited: Jun 27, 2011
    Yes. I believe that is true.
    Sorry. My bad. I was referring to plugging in and charging, (like I said in the first part of my post). The only way to significantly cool the battery is to charge it. However, this can be done at 220V @ 12A, so it doesn't take much energy. (this is specifically why cooldown was added to the Tattler, to perform this function during non-cheap TOU)

    It is mostly related to opening the charge door. If you arrive home in range mode and the car is warm, the fans will not run. But if you open up the charge door, the car will switch to standard and the fans will turn on briefly. I believe the car will also switch out of performance mode to standard when the charge door is opened. So opening the charge door to charge will typically switch the car to Standard. The temperature thresholds are lower in standard, so more cooling is performed. But as far as plugged in (and not charging) vs. not plugged in, no difference.

    As a side note, I been burned by this behavior before: E.g. I get home late. I'm in the car and I set it to range mode (for the long drive tomorrow). I get out of the car and plug in the charger. The next morning *$#3!grrr, charged in standard mode, not enough for the trip (i.e. I'll be driving 55 not 65)
     
  2. Doug_G

    Doug_G Lead Moderator

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    Under hot conditions, probably true. Under cold conditions, definitely not. The battery pack will go to ambient under very cold conditions, e.g. -20C, if the car is not plugged in. If the car is plugged in it will maintain it just above freezing.
     
  3. smorgasbord

    smorgasbord Active Member

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    #23 smorgasbord, Jun 27, 2011
    Last edited: Jun 27, 2011
    OK, so what you're saying is that charging the battery will lower the temperature, and thus be better for the battery, right?

    My Customer Advocate is telling me is that it doesn't matter - the car can sit "hot" until the midnight charge begins. The car will cool (or heat) the battery as needed whether it's charging or not.

    Also, I've been told that when charging in Range mode the car will pre-chill the battery pack so that the car can go a bit further before having to draw power from the battery to cool itself. Maybe that chill happens only at the end of the charge cycle? Can you talk a bit more about additional cooling while charging?

    My impression was that charging heats up the battery, that's why the cooling unit kicks on while charging. But, I don't know if the target temperature while charging is a) Different than the target temperature just parked, and b) Better for the battery's life. It would seem backwards to try to charge a hot battery. That would certainly make the cooling units kick in, but then they're fighting not only the initial hot state of the battery, but the heat produced by charging. I'm guessing that's why you're using a low amperage charge - so that charging doesn't heat up the battery as much, but yet forces the computer to try to make the battery cooler since it's charging.

    While I'm being a pain (and I do mean well - I'm really just trying to understand what's best for my battery), do you think car's smarts about battery temperature are non-optimal? That is, if Tesla thought that a hot battery in a parked car was bad, wouldn't they run the cooling? Or, are they not doing it because they don't want to run down the battery while the car isn't being driven and isn't being charged? If that was the case, then as long as the car was plugged in (even if not actually charging) they could turn cooling on, knowing that the car will charge in a few hours.

    Thanks for the great information, this is very interesting to me.
     
  4. Doug_G

    Doug_G Lead Moderator

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    I think that must be the case. Yesterday I wanted a little more than a Standard mode charge to ensure that I had a comfortable margin for my trip home. So I used Range mode but stopped it a bit early. The battery was quite toasty.
     
  5. scott451

    scott451 KWH-PWR#1349Sprt,S Sig#96

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    #25 scott451, Jun 28, 2011
    Last edited: Jun 28, 2011
    Yes.
    The when the key is off, the car will not "cool" the battery by itself unless it is very hot (+40C). An example, in standard mode at 80% SOC, if the battery is above 30C the pump will run continuously. So the battery can sit for hours at 35C, with only the pump running. If you charge the car, even for just <45 minutes @ 12A, the battery temp will drop to 25C. The following table from BatteryUniversity.com shows why this is important:
    attachment.php?attachmentid=2052&d=1309251354.gif
    Sure. Here's a plot that I produced when I first released my log_parser. It shows the cooling process that goes on during a [range mode @ 24A] charge:
    24A charge on 4-10-2010.GIF
    Discharging (using) the battery generates far more battery heating than charging. So the first part of the charge is to cool the battery. Notice in the above plot that the charger aggressively tries to cool the battery until it reaches a set point. After that, it only cools the battery to take away the small amount of heat added by charging.
    I think Tesla has done a very good job at optimizing battery life vs performance vs range vs customer perception.
    It's all a trade off. Take a look in your previous thread :) at my post about prolonging LiIon battery life, specifically the web links.

    All of my understanding about how the car works comes from measuring and analyzing (CAN bus, log files, VDS debug) what the car is actually doing. Don't my take my word for it, or the CA's. Take some measurements of your own, analyze the data, and post your results. We'll all benefit from your efforts.
     

    Attached Files:

  6. dsm363

    dsm363 Roadster + Sig Model S

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    #26 dsm363, Jun 28, 2011
    Last edited: Jun 28, 2011
    I'm down in Texas and during a day of moderate driving (with the car sitting outside unplugged for a number of hours), it comes back with the motor, PEM and sometimes battery one bar away from red. Do you recommend plugging in when you get home (I always do but usually charge at 9PM) and immediately charging to cool the battery? Thanks.
     
  7. scott451

    scott451 KWH-PWR#1349Sprt,S Sig#96

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    #27 scott451, Jun 28, 2011
    Last edited: Jun 28, 2011
    I wouldn't worry to much about the PEM/motor temps. If the Battery temp is on the last blue bar or higher (+40C), I would definitely plug in and charge. If the the battery is yellow or red, absolutely.
     
  8. strider

    strider Active Member

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    My normal routine is to plug in when I get home ~6:00 and charge at midnight. Normally, the coolant pump runs for awhile and shuts off until charging begins. However, although it doesn't get "Texas Hot" here, when we had a few days of hot weather I noticed that if I came out into the garage at say 10pm the coolant pump was still running. So I'm guessing that even if you're not charging it still drops the battery tamp back to some level (though being plugged in may have nothing to do with it).
     
  9. smorgasbord

    smorgasbord Active Member

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    Thanks again for all the information. I'm still digesting all the info. If the battery temp is yellow or red while the car is running, then won't the battery cooler already be on? When driving, at what temp does the battery cooler kick in (I realize this is different in Standard vs Performance modes)? If it is already on and you park the car, at what point does cooling stop? Right when you stop the car, or does it keep going until some temp threshold is reached or some time period has expired?

    If I'm understanding things, the "charge to cool" thesis is really a clever way you came up with to lower battery temps. For those of us on TOU meters, I'm wondering if it wouldn't be best to use the 120v cable to draw as little power as possible, since the goal is to lower battery temps, not actually charge the battery. And, I'm assuming your Tattler can be setup to use the lowest possible draw just to cool the battery, then shut off until the off-peak power period starts and then do a "real" charge.
     
  10. S-2000 Roadster

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    Not a bad suggestion, but keep in mind that the Tesla uses the same current limit for a given location regardless of whether the 120V cable or the 240V cable is used for charging.

    I was a little disappointed to discover this when I had to manually lower my 120V charge to 12A because I have a 15A breaker on that circuit (I'll be installing a separate 20A with new wiring eventually). After I lowered the 120V to 12A, I noticed later that my UMC was also charging at 12A. I only tested this once, though, and immediately restored the 240V to full 40A charge without using the 120V since.
     
  11. scott451

    scott451 KWH-PWR#1349Sprt,S Sig#96

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    #31 scott451, Jul 1, 2011
    Last edited: Jul 1, 2011
    Probably. You can measure this yourself. Notice when the battery temp is yellow or red, the AC is running while the car is on to cool the battery. If you turn the key off, usually the AC will stop, which is not what you want. If you sit in the car with it on, the AC will continue to run until the battery cools to 32C (in standard at 50%-70% SOC) I think. Don't quote me on the numbers, because they change with FW releases. It's better if you monitor it and post your findings.

    I haven't mapped out when the AC runs because it is complex. I have a basic understanding of how it works, but it depends on Mode, Temp, and SOC. At low SOC the AC rarely runs.

    Not really. Look at the above 24A charging graph. Notice that the current to the ESS drops by about 5A whenever the AC is on. Assuming [email protected] =2000W. So at 120V you'd need 16.7A just to run the AC and you've only got 15A. If you look at a [email protected] charge from a log dump, you'll notice the ESS current goes negative when the AC runs. In previous versions of FW, the battery was allowed to run hotter when charging off of 120V. I believe FW has changed now to cool the battery even if it means the battery is slightly depleted during the process. On the other hand, a 20A charge off of a NEMA L5-30 @ 120V would do the job nicely :smile:

    Yes. Unfortunately, the lowest current the PEM allows is 12A. (I wanted to use 9A). It's still cheap 45min*12A*240V = 2KWHrs. Worst case, at the top tier, $0.34/kwhr, it cost you $0.68 to cool your battery
     
  12. donauker

    donauker Member

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    In testing the 120V charging capabilities last night it did seem that the FW may have a higher temp threshold in lower current situations. I was not able to get the car to do battery cooling even in range mode charge when charging at 16A 120V (lowest RFMC pilot signal) but when I went to 24A 120V charge it immediately started battery cooling with a standard mode charge.
     
  13. doug

    doug Administrator / Head Moderator

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    I seem to recall reports (from a couple years ago) that with the MC120 (the old name for the "spare connector") the car would alternate between charging and cooling because it didn't have enough power to do both at the same time.
     
  14. daniel

    daniel Active Member

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    I expect to charge and drive in Standard mode 99.9% of the time. But once in a blue moon I may want to show off the acceleration to a friend. I understand that it's better for the battery to be hot during hard acceleration, but that staying hot for a long time is not.

    So let's say I'm driving for a short time in Standard, after a charge in Standard. My battery is still above 85% SoC because I've driven only a bit to pick up the friend I'm giving a ride to. On the assumption that a single brief period of sub-optimal use will not greatly affect battery life, I put it in Performance mode, floor the pedal from zero to 40 mph to feel and show off the acceleration, and then put it back in Standard mode.

    Will I actually get more acceleration? Or does the battery have to be hot in order to get more acceleration in Performance mode than in Standard mode?
     
  15. Dragon

    Dragon Member

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    I guess you'll get more acceleration anytime you switch to performance mode. How much more depends on the battery temperature AND if you charged in performance mode first.

    Correct me if I'm wrong.
     
  16. S-2000 Roadster

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    I can only guess at this point in my learning curve, but I can hypothesize. If you charge in Performance Mode, I assume that it only works if you drive right away. If you charge in Performance Mode over night, unplug, drive the car to a track in Standard Mode, and let the car sit unplugged for a while until your turn comes up, then I assume any battery temperature generated during your nighttime charge may have dissipated. In other words, I assume that a lot of this has to do with timing. If you maintain Performance Mode from charging to driving without letting the car sit, then you certainly should have the maximum torque and power. But it just seems to me like the battery can't really 'store' temperature that you create during charging, and thus I don't see how it can last unless the higher temperature is specifically maintained by everything you do between charging and driving.

    To approach the question from a different tack, I assume that Performance Mode depends upon the SoC and temperature of the battery and thus it shouldn't matter if you charge in Performance Mode so long as the temperature of the battery is at the right level. A good question is whether we can achieve the same performance from a Standard Charge, provided that we drive around in Performance Mode long enough to warm the battery up to the same level as a Performance Charge.

    Maybe it works like warming up tires. Draggers just spin the tires in place to warm them up. Lappers zig-zag aggressively for a few laps to warm the tires. Both get the 'same' warm rubber performance, assuming they're running the same rubber formulation. The analogy would be that Performance Charge allows you to heat the battery without moving the car, provided you have a charging station available. I'm hoping, though, that you can achieve the same performance from a Standard Charge and then driving a few laps in Performance Mode to heat the battery up to the required levels.

    Again, this is all hypothetical. I hope to look at some temperature logs to see if I can learn from the actual performance of my Roadster 2.5
     

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