Parking Nose Down on a Steep Hill -- Tow to Take Off !

Discussion in 'Prime Main Forum (2017-Current)' started by SubPrius, Mar 5, 2017.

  1. SubPrius

    SubPrius Junior Member

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    Gen 1s had a feature that Toyota didn't advertise.

    If you parked nose down on a really steep (S.F. type) hill, you could be stuck.
    There's an over-amperage cutout to protect the big battery. If backing up took too many amps, then you were not backing up. If you could not steer around whatever was in front of you, you were not going anywhere until the tow truck or a friend with a tow strap arrived.

    Do Primes retain this feature?
     
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  2. Mendel Leisk

    Mendel Leisk Senior Member

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    You mean the first itteration of plug-in Prius, 2012 commencement?
     
  3. bwilson4web

    bwilson4web i3 and Prime

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    You may find this article enlightening: Calculating the Force Needed to Move an Object Up a Slope - dummies

    The component of the weight of the refrigerator along the ramp is

    [​IMG]

    You may be confused as there is a well known caution identified in the Prius owner's manual to use the mechanical parking brake and not just "P" when parking on a steep incline. On a steep grade, the stress on the parking paw, the "P" part of the transmission, can exceed what it takes to disengage. There have been reports of Gen-1 cable failures between the gear selector and the parking paw that 'bricked' the car requiring a tow.

    Documented in the Gen-1 maintenance manual is a procedure to test the battery that involves a controlled, discharge. The wheels of the Gen-1 are blocked and the Gen-1 put into "R". This provides a controlled, discharge of the battery to look for weak module pairs. I don't remember seeing any accelerator limitation but it is good to know the Gen-1 won't destroy itself.

    One of the things we discussed in the Yahoo Group, Prius Technical Stuff is how to measure the traction battery capacity by running in reverse up a hill until the car runs out of traction battery energy. The change in altitude can be used to calculate the kWh. I tried that experiment but ran out of hill before battery.

    So if you have a specific location, a street address or longitude and latitude, I'll look around North Alabama to see what we have locally. We need documentation of this Gen-1 killer hill. Then we can look for something similar. Don't forget to include the total weight of that Gen-1. The force that has to be overcome a grade is roughly the sine of the incline times the weight of the vehicle. I'll share that the Prius Prime exceeds the Gen-1 power in reverse.

    One thing, snark suggests:
    a bracketed fake news alert. The best answer is to reply with a basic physic lesson on how the real world works and ask the OP, "Where is this Gen-1 defeating hill?"

    Bob Wilson
     
  4. SubPrius

    SubPrius Junior Member

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    Interesting info Bob.
    But the issue was not with the parking brake. I was actually in the hills east of Bishop CA (unfriendly Prius territory).
    After releasing the parking brake and putting it reverse, my Gen 1 did not move backwards.
    Fortunately, I had JUST enough room to steer around the rock that was in front of me.
    We pulled away, going forward, and I continued to drive it, reverse it, and parking brake it just fine for a decade.

    Mendel, it was my 2003 Gen 1.
     
    #4 SubPrius, Mar 6, 2017
    Last edited: Mar 6, 2017
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  5. bwilson4web

    bwilson4web i3 and Prime

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    Off road?

    Let me recommend getting an electronic copy of the Owner's Manual. There were references to hills and overheating:

    If “Hybrid System Overheated. Reduced Output Power.” is shown
    The message may be shown when driving under severe operating conditions. (For example, when driving up a long steep hill or driving up a steep hill in reverse.)

    If “Depress Brake When Vehicle is Stopped. Hybrid System may Overheat.”
    is shown

    The message may be shown when the accelerator pedal is depressed to hold the vehicle while the vehicle is stopped on an uphill, etc. The hybrid system may overheat. Release the accelerator pedal and depress the brake pedal.

    These seem documented instances involving a hill and the risk of overheating.

    Bob Wilson
     
  6. bisco

    bisco cookie crumbler

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    we have a lot of san fran owners, i don't think this question has ever come before. interesting conundrum. maybe take a test drive and try it out. could be an amusing situation for the salesman sitting next to you.:cool:
     
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  7. Mendel Leisk

    Mendel Leisk Senior Member

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    Our son's inlaws are on a super steep street. I've parked facing down hill, with the tire nosed into the curb. So getting started takes a mighty effort for that second or two in reverse. Maybe I'll quit angling the tire in; old habits are hard to shake though.
     
  8. SubPrius

    SubPrius Junior Member

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    More interesting info Bob.
    But it sure didn't seem to be an overheating issue.
    My Prius didn't TRY to move back and then stop. It just didn't move at all.
    It was a dirt path up to Flynn's launch site. I stopped and turned around before scraping anything.
    But, it was a Gen 1 and not a Gen 2 or later.

    Mendel, on your steep backing up, did your Prius move slowly or shutter for a bit and then started moving better?
     
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    No it was fine, not steep enough I guess. But I can see the issue: it's all down to the electric motors in reverse.
     
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  10. WilDavis

    WilDavis Senior Member

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    ...or take the salesman along to use as the chock for the wheels? :rolleyes:
     
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  11. bisco

    bisco cookie crumbler

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    to answer the o/p's question, i don't think the prime retains this 'feature'.:cool:
     
  12. David Beale

    David Beale Senior Member

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    In Pearl, a GII, I encountered a very steep hill in B.C. in Gibsons, where it required -full- throttle to back up (I was trying to turn around). Paved side street. No battery disconnect occurred in this case. The car barely moved, but it did move. May not have if I had more than the two of us in it though. ;)

    GI had much simpler batteries. I guess they needed protection, or the engineers thought they did. I think the only protection afforded to GII and GIII (and probably GIV) is temperature. And you won't over temp. them backing up for a few seconds.

    Lee can attest to full throttle not causing cut-out. He did acceleration tests in EV.
     
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