TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Power will improve as you drive

Discussion in 'Model S: Battery & Charging' started by ElectricAvenue, Dec 11, 2013.

  1. ElectricAvenue

    Joined:
    Jun 11, 2013
    Messages:
    60
    Location:
    Nashua NH
    Now that it is getting cold out I am seeing the messages
    "Battery is heating"
    "Power will improve as you drive"

    I understand the above messages, but why am I NOT see the dashed line on the KW meter on the dash which shows I am limited in the amount of KW I can draw from the battery?

    If I was limited in power should that dashed line also show up?
     
  2. MikeC

    MikeC Active Member

    Joined:
    Jul 9, 2012
    Messages:
    2,405
    Location:
    Los Angeles
    Saw that yesterday for the first time and had the same question. The car didn't feel any weaker to me, but I didn't push it because of the cold battery.
     
  3. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

    Joined:
    Mar 8, 2012
    Messages:
    12,753
    Location:
    Texas
    I've seen both but with preheating there is just the regeneration limit bar. The one time I got the power limit bar the information screen accompanied it. The power limit was almost at the top anyway, so I guess there is a point where it's just barely limited but the bar isn't there. It would make sense if the information screen also had the number on it. "Battery is heating, you are limited to 310 kW (P) 30 kW (R)".
     
  4. Doug_G

    Doug_G Lead Moderator

    Joined:
    Apr 2, 2010
    Messages:
    15,851
    Location:
    Ottawa, Canada
    Yeah the dotted lines aren't quite in the right place. Power/regen is a little more limited than shown. So you can still have a limit even while the dotted line isn't showing. For example if the regen limit is 50 kW you won't see the line, even though the maximum regen is 60 kW.
     
  5. mknox

    mknox Well-Known Member

    Joined:
    Aug 7, 2012
    Messages:
    8,561
    Location:
    Toronto, ON
    The other day, I had the power (not re-gen) limit line on for a whole trip I took of about 15 miles. It was cold, but I've driven in colder. What is that all about? FWIW I had between 30 and 40% SOC on the battery at the time. I have seen that line come and go briefly under heavy acceleration when the battery is low, but this was different with it stuck on (at about 2/3 of the scale) the whole time.
     
  6. scaesare

    scaesare Active Member

    Joined:
    Mar 14, 2013
    Messages:
    3,937
    Location:
    NoVA
    My experience is that the display of the limiting lines (both power & regen) on the dash is not always entirely consistent.

    At times I've not has a power limiter line until I floored it, and then when the orange "power needle" swung up toward max, it "revealed" a dashed power line... and then when I released the pedal it again disappeared. In other words, the car was limiting power, but the UI was only displaying it when the "shaded area" of the power meter was active at the power limit point.

    At other times I've been obviously regen-limited but never saw a dashed line.

    It's also noticeable that the dashed limit lines don't always line up with where the limiting occurs. For example, the dashed line may be indicating a regen limit of 45kWh... yet you can only achieve a regen value of about 40kWh. I'm unsure if this is just display error, or if there's some margin built in to the system to help absorb "sudden" fluctuations

    Note that these display anomalies are different from the seeming-inconsistency of when/why things are limited. Driving two different days with the same outside temperature can have different limiting applied as dictated by a variety of likely factors: outside temp, SOC, pack temp (i.e. "cold soak"), etc...
     
  7. paco3791

    paco3791 TMC OG

    Joined:
    Nov 10, 2006
    Messages:
    366
    Location:
    Antioch, IL
    #7 paco3791, Dec 12, 2013
    Last edited: Dec 12, 2013
    In addition to the comments already made here i will add that while I consistently see the dashed limit lines in cold temperatures before the battery pack comes up to nominal operating temps I DO NOT get the "battery is heating" warning, mentioned by the OP, when I have "range mode" selected. it appears as though, in range mode, the pack will just gradually heat itself using the normal heat from discharging the pack under normal driving conditions. As soon as I turn range mode off the HVAC system inside the car kicks into high gear and I'll get the "battery is heating" warning. So far, for me at least, this has been very consistent, even with the very low ambient temps we have been getting recently in the Chicago area. My guess is that even with range mode engaged there is a low threshold that would eventually trigger the battery heater to make sure the battery pack isn't damaged but I haven't found it yet, even with cold soaking the car at work for 4-6 hours in near 0 deg. F temps.

    From everything else I've read on this forum it doesn't sound like this is typical behavior but I don't know if that is because most people are not driving in range mode all the time like I usually had been or because my car is acting differently for some unknown reason. It's only been recently with the truly frigid temps that I was prompted to switch out of range mode because it couldn't keep up and the car interior was getting less comfortable. How does everyone else use range mode in winter driving?
     
  8. Doug_G

    Doug_G Lead Moderator

    Joined:
    Apr 2, 2010
    Messages:
    15,851
    Location:
    Ottawa, Canada
    Yes it is inconsistent. I've had the power-limit line appear at startup, then disappear, and then reappear again. In fact once last winter I even got the "Power is limited" warning message twice; the second time after the power limit had mysteriously disappeared.
     
  9. rlang59

    rlang59 Member

    Joined:
    Feb 27, 2013
    Messages:
    923
    Location:
    US
    This is correct and seems to be how the system works.
     
  10. paco3791

    paco3791 TMC OG

    Joined:
    Nov 10, 2006
    Messages:
    366
    Location:
    Antioch, IL
    Thanks for the confirmation rlang. makes me wonder why everyone gets so bent out of shape about the battery heating taking up so much power during the start of a drive. Preheat the battery off shore power when you can, but if range is paramount just turn on range mode and you don't have to worry about the pack heater. True, cabin temp comes up much slower but until it got to single digits around here I honestly didn't even think about it.
     
  11. ElectricAvenue

    Joined:
    Jun 11, 2013
    Messages:
    60
    Location:
    Nashua NH
    Paco, just to let you know I have been driving without Range mode set. So I will try Range mode now an see.
    Thanks.
     
  12. paco3791

    paco3791 TMC OG

    Joined:
    Nov 10, 2006
    Messages:
    366
    Location:
    Antioch, IL
    #12 paco3791, Dec 13, 2013
    Last edited: Dec 13, 2013
    It's good to experiment ElectricAve. :biggrin: But I am honestly interested in what effect NOT heating the batteries has. My, limited, understanding of batteries is that extreme hot temps are much more damaging to the long term health of the batteries than extreme cold temps. I have to assume that Tesla's software would put up more of a stink when enabling range mode if it were degrading the batteries.

    I also think that when the batteries are in their nominal operating temp band you ARE going to get more performance/range out of them. but it's balancing act. At some tipping point the energy your using to heat the pack out weighs the extra performance/range your going to get out of the pack because it's up to temp. Just like there is a tipping point between driving slower and using the cabin heater for longer, etc. From what I can tell the pack being up to temp, in cold weather specifically, has a much bigger impact on "performance" (read accel and regen, or charge rate and discharge rate) than on range (read actual watts available). This balancing act is most likely different in hot temps. I will depend on the kindness of others to back up my argument with actual data. :tongue:

    The other thing to remember is that your regen capabilities are going to be severely limited in cold temps with range mode enabled, especially if you don't/can't preheat the pack on shore power, but that's a small price to pay if you need the extra range or really want to keep you Wh/mile down.
     
  13. ElectricAvenue

    Joined:
    Jun 11, 2013
    Messages:
    60
    Location:
    Nashua NH
    Pace, I did another test last night.
    It was 9 degrees F last night and dropped to 1 degree this morning. I left the MS on the driveway and charged it when I got home yesterday evening with a 110V outlet.
    The battery charged at 3.2 miles/hr, the inside temp dropped from about 55F to 9F
    At 7:30am I turned on the cabin heat to 65F for 35 mins.
    When I got in the car to drive, I got a message saying regen was disabled.
    So I assume even at 1degree F outside temps, charging with 110V there was very little preheating going on. (maybe because there is only 1KW available with 110V?)
     
  14. rlcordeiro

    rlcordeiro Member

    Joined:
    Apr 3, 2013
    Messages:
    43
    Location:
    California,United States
    ElectricAvenue
    When did your car complete charging? I think the battery cools down when not actively charging or discharging. Running the heat on shore power will prevent the battery from discharging leaving it cold.
     
  15. ElectricAvenue

    Joined:
    Jun 11, 2013
    Messages:
    60
    Location:
    Nashua NH
    It did not finish charging, I stopped it manually when I was ready to drive.
    Also, when I started the cabin heat, I saw from Visable Tesla that there was actually current being drawn from the Battery instead of it being charged, and yes it was plugged in.
    I just think the charging and cabin heat was too much power for the 110V supply.
     
  16. riceuguy

    riceuguy Member

    Joined:
    Dec 17, 2012
    Messages:
    169
    Location:
    Austin, TX
    I had this happen for the first time the other day; the variable was that the car had been in the cold for 2 straight days!
     

Share This Page