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The effect of Performance mode on battery life

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

  1. raymond

    raymond Member

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    My bad. I mis-filed the quote below in a lesser quality part of my brain:

    But to get to the point: your experience is that performance mode is available as soon as you select it? Why would Tesla limit the max torque in standard mode? If I want to go fast, I press the pedal all the way; if I want to go not-so-fast, I don't. Those few seconds of acceleration won't fry the battery (I think). Sustained high-power driving causing a hot battery will shorten the life span of the battery, so I understand that requires an explicit choice to be made (by selecting performance mode).
     
  2. vfx

    vfx Well-Known Member

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    So Performance Mode is unfriendly to battery life. I am I correct here?
    I believe it's only bad for the battery if the car's battery pack is allowed to get hot and stay hot -which is what Performance Mode allows. So if you don't charge in Performance Mode then before puttering* around in the city for 20 minutes without any (or few) wildly fun accelerctions while in Performace Mode would not hurt anything since the battery would not get hot. Or will it?
    Scott is there a way to tell when the battery has crossed over into "Degradation Mode"?


    *Can you even really "putter" in and electric car?
     
  3. dsm363

    dsm363 Roadster + Sig Model S

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    That's my basic question too. I really never have to charge in Performance mode. I just would like to charge in Standard mode and then every now and then put it into Performance mode for a few seconds. Do you get the 0-60 in 3.9 seconds with that setup?
     
  4. smorgasbord

    smorgasbord Active Member

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    Teslas don't putter about town, they whir about town.
     
  5. scott451

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

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    #5 scott451, Jun 19, 2011
    Last edited: Jun 27, 2011
    In general, yes. Performance mode allows the battery to run hotter to get more power out of the battery. I have a 2008, and FWICT, there is no difference in torque between standard and performance. At least I've never notice getting less power in Standard. On the 2010 sport there is definitely a difference.
    It's more complicated because there are two bad things you are trading off against. High temperature and high current draw. To get the most power from the battery (and do the least "damage"), you want the battery to be hot (40C) and fully charged. Leaving the battery hot and fully charged degrades the battery over time. The opposite, a cold, fully charged battery driven in performance mode is probably worse because for the same power the PEM will draw even more current to compensate for the lower battery voltage. But the worst case of all is a cold battery at less than 50% SOC in performance mode. The internal resistance of the battery is higher at low SOC causing more battery heating. So if you drive in performance with a cold, <50% SOC battery, the battery will deliver larger current and it will also experience rapid heating of the battery.

    I think Tesla has it right. If you are using Performance mode, make sure the battery is warm and fully charged. When you are done, plug it in. (charge it in standard to cool it back down). When you are below 50% take it easy on the accelerator, and don't drive in performance mode.

    When the third blue bar on the VDS battery screen comes on, that means the battery is at 35C. The fourth means 40C. So for performance, it's probably good have the third bar on. For standard driving, I try to charge whenever I notice that the third bar is on, or the SOC has fallen below 50% YMMV.

    So the roadster battery doesn't like to be rode hard and put away wet :smile: So that spirited drive to the grocery store in performance heating the battery to 40C and then left in the garage for 5 hours waiting to charge at the cheap TOU, means the battery spent 5 hours @ 40C. When in doubt, plug it in [and charge it]!
     
  6. S-2000 Roadster

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    #6 S-2000 Roadster, Jun 19, 2011
    Last edited: Jun 19, 2011
    So how long does it take for the third blue bar to come on after switching from Standard to Performance mode? I'm assuming that Standard mode usually has fewer than three blue bars.

    Is it enough to just plug it in, or should you specifically be charging? You gave an example of waiting to charge at cheap TOU, but did you mean plugged in with the car programmed to start charging later, or did you mean completely unplugged? I realize that was a hypothetical scenario, but I'm trying to understand.

    I always plug in my roadster because I'm never in my garage at 3 am. But does that mean the battery stays hot? Wouldn't the normal circulation of battery current bring down the temperature, albeit slowly? I've certainly heard the front fans turn on at high speed for a second or two when first plugging in, and then they go quiet.
     
  7. smorgasbord

    smorgasbord Active Member

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    My car thinks it knows when I'm about to go for a drive. When I disconnect the plug, or open the trunk, or open a door, the battery temperature system kicks in.

    So, why wouldn't the car know you're done driving by locking the doors or plugging it in (even if charging isn't set to begin until later)? I haven't run any tests to see what is going on, but from the noises it makes I think the car is trying to cool down the battery after a spirited drive.
     
  8. S-2000 Roadster

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    Good questions and good topic.

    I must admit that I am confused by Tesla Motor's "Designed to be plugged in" comments in the manual, at least when combined with the timed charging mode. In other words, if you plug in a Tesla Roadster and the screen says that charging is scheduled for later, what sorts of activities does the car perform until then? ... and which of those would not be performed if the car were parked unplugged?
     
  9. Doug_G

    Doug_G Lead Moderator

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    From what I've seen, if the car is very cold and you plug in, it will immediately close the contactors and preheat the battery pack, even if it's on delayed charging. I think that is done to maintain regen.

    I've certainly heard it running the cooling system after I've parked, but when it's hot I've yet to hear it close the contactors upon plugging in. Maybe someone in a hotter climate can comment.
     
  10. cinergi

    cinergi Active Member

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    FWIW, I've had the fourth battery temp bar come on in STD mode while on the highway in the evening (about 70F outside). I didn't hear the a/c trig to cool it down, either ...
     
  11. richkae

    richkae VIN587

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    #11 richkae, Jun 19, 2011
    Last edited: Jun 19, 2011
    A few days ago I spent the day lapping at a racetrack. ( Go-kart track, 0.9 miles, 18 turns, my max speed was about 74mph )

    My car is an early 2.0 non-sport.
    I drove in performance mode. In between sessions I charged in standard mode 240V 40amps.
    I ended each session when I hit the power limit due to motor temperature.
    Ambient temperature was about 24C

    It took about 7 minutes of hard driving to hit reduced power due to motor temperature.
    A typical session the motor would start at 61C and then hit 147C and then I would do a couple cool down laps.
    It would take about 4-5 minutes for me to stop and plug back in. About 18-20 minutes later the motor would be down to 61C and ready to go again.
    The PEM would start out at 35C and peak out at 45C, but be back down to 35C by the time I parked.
    The ESS would gain about 9-10 C by the end of the session. An early session it started at 24C, was at 33C when I stopped, but be back down to 28C after 18 minutes plugged in. So each session I drove, the ESS gained a little bit of temperature, slowly climbing during the day.
    The later sessions it started between 28C and 30C and peaked out at 38C or so.

    If I had charged in perfomance mode, the ESS would have cooled less. I believe that I would have gotten slightly more power out of it because of that - but that does not seem worth it because getting it hot reduces its life.

    The next time I go, if the battery approaches 40C I will charge in range mode to cool it down a little more in between sessions.
     
  12. S-2000 Roadster

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    Is there any documentation showing the Range mode keeps the battery cooler during charging? I thought it would have to allow more heat to build up in order to reach 100% charge. My assumption is that Standard mode is the coolest when charging, but it stops at 90% full. Range most seems to be designed to reach 100% charge, not necessarily to charge at a cooler temperature.
     
  13. smorgasbord

    smorgasbord Active Member

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    I don't have anything handy, but that was confirmed to me by my Customer Advocate. The idea is to use line power to pre-cool the battery, thus saving the need to pull juice out of the battery to cool it.
     
  14. S-2000 Roadster

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    Nice! When charging in Ellensburg, Washington, recently, I used Range mode until the current dropped below the full 70 A. Thus, I supposedly avoided any of the drawbacks of charging to 100%, but still gained the advantage of a pre-cooled battery.
     
  15. Nik

    Nik Dreaming no more :-(

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    I think one would trickle around in an EV.
     
  16. vfx

    vfx Well-Known Member

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    I'm going to go with "buzz".
     
  17. daniel

    daniel Active Member

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    Yes, definitely. In my Zap Xebra I can do nothing but putter. Well, it doesn't putt, but it kind of klunks and clanks. But (sorry to get pedantic here) "putter" in common usage doesn't mean making putt-putt noises so much as it means to go slowly here and there, semi-aimlessly. Not every EV is a Roadster. Once I have my Roadster, I will switch from puttering about in my car to zapping around in my car. Zap Cars had a reason for choosing that name, even though, like the so-called "Delicious" apple, the name is grossly misleading.
     
  18. bolosky

    bolosky Member

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    I was at the same event as Rich, and I also have an early 2.0 non-sport. I did something very similar to him, except that I drove and charged in standard mode, I didn't use performance mode at all.

    My motor was hitting overtemp at 139C rather than 147C, so we can assume the difference is the extra room that you get out of standard mode. It seemed to cool pretty fast to around 60C and then plateau. My battery typically would warm up to ~33C and then cool back down into the high 20s by the time I was ready to go back out on the track.

    The hottest that the battery got during the day was 40C. This happened not at the track, but on the drive home. I drove a fairly long distance between finishing at the track and getting home. By the time I made it home, my battery was down to about 20% in standard mode. The last leg of the drive is on 70mph freeway (meaning I went about 80). The battery heated up to 40C, a good bit warmer than it ever got on the track. I can only assume that this was because the lower state of charge combined with the current draw to drive pretty quickly for a few miles resulted in a lot of internal heating.
     
  19. richkae

    richkae VIN587

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    Bill, I'm not sure what the temperature threshold was that limited power due to overtemp of the motor. It could have been the same as yours. I tried to finish the lap I was on as fast as I could so the temperature kept going up and the 147C I reported was the peak.
     
  20. smorgasbord

    smorgasbord Active Member

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    Scott, I just had an email exchange with my Customer Advocate, who said that there is no temperature difference behavior when plugging the Roadster in versus letting it sit. The only difference is that if it can, the car will use line power instead of battery power to heat/cool the battery. He told me I would do no damage by having the car wait many hours for the cheap power. They just don't want it unplugged for long periods of time. Thus, I believe that if you park the car with the battery temp at 40C, the cooling system will engage whether or not the Roadster is plugged in and getting power.

    Can you explain what differences in battery temps you've observed plugging the Roadster in versus not? Could this be something they've improved on later models/firmware?
     

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