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Can I use my MS to jump start another car (an ICE)?

Discussion in 'Model S: Battery & Charging' started by astrotoy, Oct 26, 2013.

  1. astrotoy

    astrotoy Member

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    If so, where do I look for the battery terminals to connect the cables? Thanks.
     
  2. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    No.

    There are terminals behind the nosecone to "jump start" the Model S in case it is disabled. However, the DC-to-DC converter in the Model S is not designed for, and doesn't have the capacity to give an ICE the burst of power it needs to jump start.

    In theory, it could charge an ICE battery in a tough pinch, but you'd be sitting there for a while.
     
  3. jerry33

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

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    It's strongly not recommended. The best plan for playing good samaritan is to purchase a jump box. The 12V system in the Model S (and other EVs and hybrids) is not designed to cope with a starter motor. However, in a real emergency--in this case "real emergency" means you are 100 km from anywhere, the other car must be started, and there is no other possible solution--you can try the following:

    1. Take the keys from the other person and turn off the dead car. It's vitally important that the receiver car does not attempt to start while the two are connected. Be sure the two cars aren't touching.

    2. Remove the nose cone of the Tesla.

    3. Attach the red cable to the positive jumper terminal first to the dead car, then the Tesla. Be sure that the ends of the cables don't touch anything other than the connection points.

    4. Attach the black cable to the negative terminal of the dead car and to a metal part of the Tesla.

    5. Leave the cables connected for thirty minutes.

    6. Disconnect the cables in the reverse order that they were connected.

    7. Try to start the dead car.

    Basically you aren't really jumpstarting, you are trying to charge the drained battery enough so that it will start the car. If the procedure is done incorrectly you will cause a lot of damage to the Tesla. It's a real desperation move and no guarantee that it will succeed. You could end up with two non-fuctional cars instead of just one.
     
  4. astrotoy

    astrotoy Member

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    Thank you.
     
  5. wts13

    wts13 Member

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    For $100 or so you can purchase a portable power unit that will make this unnecessary :) Put a calendar reminder on your phone to top of the charge every couple months and you'll never be in this situation. We always kept one of these in our '99 Suburban that was notorious for not starting at the most inconvenient times.
     
  6. Nickjhowe

    Nickjhowe Member

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    @[email protected] - can you confirm the source of your statements? At least one of the Tesla TechTalks stated that the front posts can be used both to jump the Model S, and as a source of power to jump ICE cars.
     
  7. Cosmacelf

    Cosmacelf Active Member

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    The Tesla 12v battery is a small deep cycle battery. It is not designed to put out lots of current quickly for a starter motor. In addition, taking off the nosecone isn't an easy thing to do.
     
  8. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Directly from the service center; and, even if I hadn't heard that, from personal knowledge and experience. The entire 12V system in the Tesla Model S is not designed to deliver the several-hundred cranking amps required for an ICE starter motor; the 12V battery is very small and designed to keep auxilliary equipment powered, and the DC-to-DC converter is only designed for double-digit amps @ 12V.

    If you keep the Model S powered up, it's likely that the DC-to-DC converter could supply enough current to charge an ICE battery, but it will be like a fast battery charger rather than a jump starter. You'll likely need about 20-30 minutes of charge time for a dead ICE battery (much more for a larger vehicle, like a diesel truck), and as Jerry said, NEVER try to start the ICE while attached to the Tesla or you could cause damage to the Tesla.
     
  9. brianman

    brianman Burrito Founder

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    Point of clarification:
    Is it also a bad idea to attach your Tesla to a running ICE? (Or is the issue just while the ICE is being started?)
     
  10. jerry33

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

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    You are never supposed to connect any car while it's running. As far as I know, that's a safety practice rather than an electrical one.

    - - - Updated - - -

    I wasn't there, but I'm sure he meant to supply power to charge a dead battery rather than a traditional jumpstart. There just isn't the capacity in the 12V system to handle the power surge of a starter motor. A few folks tried a traditional jumpstart using their Prius, which has a similar 12V system, and the best that happened was they blew the rather expensive 100 amp fuse. Some actually damaged the inverter. There is nothing that leads me to think the Tesla will be any different in that regard.
     
  11. richkae

    richkae VIN587

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    In the standard automotive parlance "jump starting" is providing another source of 12V power so that the starter motor can crank the engine.
    The reason jumper cables are so thick is that several hundred amps go through them for a few seconds.
    Using this term with the Model S is misleading. All the 12V system needs to do in the Model S is power up some electronics - and probably doesn't exceed a couple of amps ever.

    Just like the Model S, the Prius does not crank a starter motor with the 12V system. The Prius uses its main pack to turn one of the electric motors in the hybrid system, the 12V is just used to power up the computers.
    I have "started" my dead Prius with a 12V lantern battery when its 12V battery was dead ( and the main pack was fine ).
    A lantern battery is probably an adequate backup source for a Model S as well, but it will never crank an ICE starter motor.
     
  12. brianman

    brianman Burrito Founder

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    Interesting. I've had multiple situations in previous ICE vehicles where (a) my car wouldn't start (from dead) without the other car running (even after waiting 15 minutes or so) and (b) other car owners were not comfortable jumping my car without theirs running (for fear they would drain theirs).
     
  13. mknox

    mknox Well-Known Member

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    Imagine having an electric car with an 85 kWh battery and having to tell the poor sap with a dead ICE that your car doesn't have the capacity to boost it. :wink:
     
  14. woof

    woof Model S #P683 Blue 85 kWh

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    Imagine that same poor sap if you could connect the full power of the Model S in its 400+ Volt Li-ion glory to his measly 12 Volt system! :scared:
     
  15. jerry33

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

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    Once the cables are connected, you can start the donor car. It's just while making the connection that both should be off.
     
  16. brianman

    brianman Burrito Founder

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    Ok, let me try again.
    If you follow the steps in jerry's quote here and the Model S doesn't wake up (enough to enable the 17", open the charge port, and/or enable tow mode) 10 minutes, what's the recommended approach to getting a Model S (with drained 12V) attached to a running ICE so that the process of waking up the Model S happens before the sun explodes?
     
  17. markwj

    markwj Moderator, Asia Pacific

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    I had a guy ask me (very politely) whether he could get a jump start from my Roadster. I told him that the roadster is 400 volts and would fry his little 12V battery. It seemed a simpler way of saying 'no' than going into the details.
     
  18. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I'm confused (but what's new) at what you're asking here - jerry's instructions were for charging an ICE with a dead battery from a Tesla Model S.

    If the 12V system is dead in the MS, it should wake up the instant 12V is applied to its terminals, because the contactor will close and the DC-DC converter will immediately begin powering 12V electronics. It'll happen without the donor car even running.
     
  19. brianman

    brianman Burrito Founder

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    This is not always the case. Personal experience in 2012. Until the tow truck was running, we couldn't get the 17" to wake up and the charge port to open. Jump pack didn't work (~30 minutes), non-running truck (~10 minutes) didn't work. Running truck woke up the S in seconds.
     
  20. richkae

    richkae VIN587

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    #20 richkae, Oct 28, 2013
    Last edited: Oct 28, 2013
    Should put a meter/scope on it and see how much it really needs to wake up.
     

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