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Tow Mode

Discussion in 'Roadster' started by vfx, Jun 7, 2009.

  1. vfx

    vfx Well-Known Member

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    #1 vfx, Jun 7, 2009
    Last edited: Jun 7, 2009
    Talk of a driver needed to be towed because of running a car out of charge.

    In order to tow the Roadster the VDS screen can help the driver release the paw that locks the transmission to allow the car to run safely and freely.

    If a driver were to run his or her battery totally empty then how would there be enough energy to move the paw? Presumably on an electrically powered solenoid of some sort.

    For that matter would the VDS even work?
     
  2. TEG

    TEG TMC Moderator

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    #2 TEG, Jun 7, 2009
    Last edited: Jun 7, 2009
    If it is like my RangerEV, the computer will lock out driving functions before the pack is so run down that it can't provide 12V anymore. You can probably run the VDS for quite a while after the car refuses to let you drive it.
    I think it would be unheard of for the batteries to go completely 'dead'. The computer has to stop letting you drive when it knows that pack is so low that further driving will damage the batteries.

    I know when you get stuck at the side of the road you might wish you got that extra mile or two of range, but would it be worth a $15,000+ battery pack just to avoid walking a little?

    If you managed to let the pack get so low that it can't even power up the VDS then I wonder if you could recharge it at all. It might have to go back to 'home base' for some sort of 'pack bootstrap' procedure.

    I think if it runs down to the point of refusing to drive, it would probably be a good idea to start charging it (via tow regen, or on charger) ASAP.

    (BTW, Tow regen was something I asked about on the TMC blog in the early days... I wonder if I had anything to do with them offering it).
     
  3. AnOutsider

    AnOutsider S532 # XS27

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    What's tow regen? Is it where the batteries are charged by the rotating wheels as the car is being dragged?
     
  4. WarpedOne

    WarpedOne Supreme Premier

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    Engineers were smart enough to program the computer to stop at 20% SOC in Normal mode or around 10% in Range mode. Of course, the label will say Empty but there will be about 5kWh left in there.

    If you than leave the car for couple of years standing in the sun it wil discharge to empty and battery will die.
     
  5. Chris H.

    Chris H. Member

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    #5 Chris H., Jun 7, 2009
    Last edited: Jun 7, 2009
    I was under the impression that out of the ESS's 11 "sheets" of cells that 10 of them provided motive power, and that 1 was dedicated to providing power for the other systems on the car (such as heating/AC, audio, lights, VDS, etc.). Did this change? Am I remembering this information incorrectly? Did I dream it? :confused:

    btw vfx, congrats on getting your Roadster... :biggrin:
     
  6. TEG

    TEG TMC Moderator

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    There have been a couple of discussions about that.
    I always assumed it was a DC/DC converter stepping down the full pack voltage, but I don't think we ever got a clear answer either way.

    There was some discussion here
     
  7. TEG

    TEG TMC Moderator

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    Yeah, that was the basic idea. The idea I had in mind was for RV drivers pulling their Roadster behind their RV on a long trip. It seems using Regen between stops could allow you to always have a full Roadster when you stop somewhere.
     
  8. Cobos

    Cobos S60 owner since 2013

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    Towing the Roadster does work. That's what the Ferdinand Motors team did with their Roadster on the EVS race. The last day they were down to about 20% charge and had a whole day of driving left. So they got a towtruck to tow it for about 1-2 hours that night and that got it back to about 70-80% charge...

    Cobos
     
  9. WarpedOne

    WarpedOne Supreme Premier

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    I don't see how or why "tow charging" via regen wouldn't work.

    Except for inclination sensors saying to computer "we cannot possibly be regenerating for front is way higher than back". It should also charge the battery faster than even HPC. Regen goes above 30kW as new power gauge is labled to 40kW. Towtruck will burn quite some more fuel though.
     
  10. AnOutsider

    AnOutsider S532 # XS27

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    haha was that even allowed?
     
  11. TEG

    TEG TMC Moderator

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    If you left the key in the ignition with everything on, and you used a tow bar with all 4 Roadster wheels on the ground then yeah, it probably couldn't tell the difference from rolling down a hill. But there might be some optimizations you could make if you were going to create a real "car being towed" mode. Some things might be:

    #1: Lock out the accelerator pedal so if someone jumped in and tried to drive nothing would happen.
    #2: Allow the key to be removed and the steering column locked. (If you park no one can reach in and grab the keys).
    #3: Make the brake lights activate only when the VDS notices that the vehicle is slowing down. (If regen normally triggers the brake lights, you don't want it to constantly show brake lights when the tow vehicle is maintaining speed).
    #4: (Perhaps not possible). Detect if going uphill, and stop doing regen so that the tow vehicle doesn't have to work as hard during times when it needs full power.
    #5: Don't do any regen at speeds below 30MPH. The tow vehicle may need power for getting on an onramp, or stop and go city traffic, so tow regen is probably only appropriate when cruising on a highway.
    ...just some ideas...
     
  12. vfx

    vfx Well-Known Member

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    #12 vfx, Jun 8, 2009
    Last edited: Jun 8, 2009
    Owners manual Warranty Guide page 4.

    What is not covered

    General exclusions

    The New Vehicle Warranty does not cover damage caused by:

    * [accidents]
    * [car washes]
    * Towing the vehicle instead of transporting the vehicle on a flat bed
    * [theft]
    * [explosions]
    *
    *
    *
    *
    *
    *
    *
    *
     
  13. Palpatine

    Palpatine Banned

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    What about involuntary towing?

    If a Tesla Roadster were parked illegally and was towed away without being set to tow mode on the VDS, would this damage the Tesla Roadster?

    Towing companies typically are liable for damage they cause during towing. The courts have ruled on this issue consistently to the point that it is accepted as common law by insurance companies.
     
  14. johnr

    johnr Member

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    AFAIK they always use flatbeds for that. So it's likely not a problem.
     
  15. Tdave

    Tdave Member

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    Manual says don't even tow/winch it onto a flatbed without engaging tow mode.
     

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