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Battery reserve and real world range

Discussion in 'Model S: Battery & Charging' started by vbsdan, Sep 30, 2012.

  1. vbsdan

    vbsdan Member

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    Today I drove my Model S until it was showing two miles of range remaining. I wanted to see what messages or warnings I would get as I got close to empty. Like the Roadster the battery icon goes from green to yellow to red as the battery is depleted, but the yellow and red show up later (when the battery is more depleted) in the Model S. If I remember right yellow is somewhere in the 20s and it didn't turn red until I was down to four miles of range.
    Other than that there are no warnings, no pop-ups, no chimes - nothing. I'm just guessing here but there's probably some reserve when you hit zero, just like in the Roadster (in standard mode, at least). I charged in range mode before leaving and at the end of the trip it showed that I had used 77.4 kwh, so again, looks like there's a reserve somewhere. What I'm wondering is: Do you have to do anything to access this reserve? Is it like driving a gas car with the fuel gauge way below empty, or do you have to call Tesla Roadside Assistance for help? Another guess, but it's probably the former. The warning messages probably start popping up when you get to zero range indicated. I'm not quite confident enough to test this theory. Anyone know if I'm right?

    This is unrelated, but if anyone was wondering the car was showing 273 miles of range when fully charged in range mode, and I drove 240 miles with two miles of range indicated at the end. Mostly two lane highways and city driving, not much interstate, so the actual to ideal ratio was pretty close to what I'm used to getting in the Roadster.
     
  2. dsm363

    dsm363 Roadster + Sig Model S

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    You're really testing the limits! This is great information, thanks. There is no reserve that you can access like in the Roadster. Zero is zero from what I understand. You'd likely have to call Roadside assistance for a flatbed truck.
     
  3. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Or carry a 2kW generator in the back. 120V*12A=1.44kW, so a 2kW generator will work fine. If you do this on neighborhood streets near your house, you should just be able to pull over after hitting zero, put in a few miles with the generator, and drive home.

    Sounds like an interesting experiment. I did a similar thing with my Prius once, but carried a gallon of gas with me. The Prius would let you drive a few miles on its battery after running out of gas. I wanted to watch the process. My 17 year old daughter thought I was nuts...
     
  4. Doug_G

    Doug_G Lead Moderator

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    It's well-known that the Roadster refuses to charge from the vast majority of generators. Best test before you try that!
     
  5. sublimaze1

    sublimaze1 8Dec2012 / Leeroy Jenkins

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    This would be an EXCELLENT software upgrade: I don't think we (owners) would mind having the option to reduce our range by ten miles if, say, we were to have a 10 mile reserve program running in the background.
     
  6. ElSupreme

    ElSupreme Model S 03182

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    But if you know it's there you won't care about 0 miles to empty My VW GTI has an estimated distance left on a tank. I know though expierence that I have AT LEAST a gallon of fuel left (I think it is generally just shy of 1.5 gallons left) when my computer has 0 miles to empty. I regularly drive 10-20 miles after hitting the mythical 0 miles to empty.

    Granted if you loaned your car to someone without that knowledge it would work.
     
  7. sublimaze1

    sublimaze1 8Dec2012 / Leeroy Jenkins

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    I guess it is the same as running out of gas - I know I never have run out of gas (although I came very close in the Citroen last year with a bad ground on my fuel ga - gotta get that thing fixed).
     
  8. drees

    drees Active Member

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    If you really want to drain it without worrying about getting stuck on the road, park near a plug in a well ventilated area, open all the windows, turn the heat/defroster up to max and see what happens...
     
  9. vbsdan

    vbsdan Member

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    I still think there's probably a "hidden" reserve. My 240 mile drive from full range charge to near zero used 77.4 kwh, or 91% of 85 kwh. We've always been told with the Roadster that standard mode uses the middle 80% of the battery's capacity and that it's best to not use the top or bottom 10% (available in range mode) unless it's really needed. If there's no reserve on the Model S then every time we ran it down close to zero range we'd be using the bottom 10% of the battery, which I assume is not good for the Model S either. Also the Model S is being marketed as more of a mainstream car, so if anything you would expect more warnings as the battery gets depleted, not fewer. Your average Joe Blow knows that he can run his gas car when the gauge is below empty and would probably expect the same from an EV. Again, all just speculation, and either way nothing good can come of driving when the range gets below zero, even if it's possible, so I'm not going to be the one to test my theory. Let Joe Blow do it.
     
  10. dsm363

    dsm363 Roadster + Sig Model S

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    There is a hidden reserve but it's not accessible to the driver if I understand it correctly. It's what allows the Model S to sit for an entire month on 'empty' and not toast the battery. They probably save the last 5% or so but that's just a guess. Maybe someone has the actual numbers. It does sound like the need more obvious warnings near zero.
     
  11. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Yes, test first. The good Honda, Yamaha, etc. inverter generators should work fine.
     
  12. Todd Burch

    Todd Burch Electron Pilot

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    Curious why you think more obvious warnings are needed. In an ICE, the fuel light goes on, but that's it. No chimes, buzzers, or anything like that. Why would the Model S be different? I suppose because it can...but maybe Tesla was thinking more of following the traditional ICE behavior here? If anything, I'd think EV drivers would be much more aware of range remaining than an ICE driver!
     
  13. dsm363

    dsm363 Roadster + Sig Model S

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    I haven't driven the Model S that low but I'd certainly notice it. Everyone is different though. I can see how someone might not notice the subtle notices if thy weren't paying attention.

    The main difference is that ICE drivers can get AAA to bring some gas while we would have to get put on a flatbed.
     
  14. W.Petefish

    W.Petefish Active Member

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  15. Zextraterrestrial

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    Vbsdan- Do you have the current software update running? I thought that 'Tesla' changed the range showing and calcs so it starts at a 265mi for full charge vs 300mi which is 'realistic' at 55 mi w/ good conditions.
     
  16. dsm363

    dsm363 Roadster + Sig Model S

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    Just updated to that tonight. A 'full charge' will now be based on the EPA 265 mile 5-cycle test range. They should probably start advertising that on their options and pricing page as well.
     
  17. Zextraterrestrial

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    5 cycle seems lame-
    who really uses an AC in a car anyways? oh, Texas & not the northwest coast (although it was a flaming 71+ degrees today on the beach in Crescent City, ouch)
     
  18. strider

    strider Active Member

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    Yep, works just fine on the Roadster anyway:
    Hack-charging on a generator - Page 3
     

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  19. jkirkebo

    jkirkebo Model S P85+ VIN 14420 EU

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    Depends on which ICE. My VW TDI will sound a "ding", flash yellow graphics at me and peridically display the message "refuel now!" when less than ~60 miles of range is remaining.
     

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