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Charging while moving?

Discussion in 'Technical' started by Cyberax, Nov 20, 2015.

  1. Cyberax

    Cyberax Member

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    I'm seriously considering attaching a trailer with a generator to my Model S to make it possible to drive from Seattle to Alaska.

    There are several generators available out there that can fit the purpose. For example: Generac 5735 GP17500E - 17,500 Watt Electric Start Portable Generator It's lightweight enough to put on a trailer that can be towed by a Model S with an Ecohitch. I have even tested this generator at a local dealership, it works perfectly at 40 amps with a NEMA 14-50 plug.r

    Of course, the next question is: "Can I charge while driving?"

    So I'm wondering how exactly the "charge cable connected" interlock works. Is it possible to work around it by connecting to one of my installed dual chargers?

    It's also quite likely that this insane mode will cause all kinds of calibration issues for the BMS sensors, but I can live with that.
     
  2. brianman

    brianman Burrito Founder

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    Prevented by Tesla firmware since at least November 2012.
     
  3. Cyberax

    Cyberax Member

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    So somebody had actually tried that? Wow.

    But how do they implement that? By measuring current from the charger or maybe charger communicates with Tesla ECU through the CAN bus?
     
  4. brianman

    brianman Burrito Founder

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    When the charge port has a cord connected, the car won't go into D(rive) or R(everse).
     
  5. Cyberax

    Cyberax Member

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    Sure. But I'm going to bypass the charging port and connect directly to the charging controller.
     
  6. FlasherZ

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

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    Charger has to be told by firmware to start charging, and the firmware controls the charging current. I can guarantee it's not just a matter of applying voltage to the terminals downstream from the charging port and <insert magic here>.
     
  7. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    Buzz. Full stop. Next idea? :)
     
  8. miimura

    miimura Active Member

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    You probably have to implement an external DC charger and connect directly to the battery. The CHAdeMO mod for the RAV4 EV does this and the car charges while the car is "READY" so that all the coolant pumps and BMS are working. However, in that case, you are tethered to a stationary charger, so they have interlocks so that if you step on the brake (to put it in gear) or release the parking brake, it will immediately cut the charging session.
     
  9. Cyberax

    Cyberax Member

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    Sure. The charger is likely connected to the CAN bus and is controlled by the firmware. However, it still might be possible to impersonate the firmware and cause the charger to do the voltage up-stepping.

    It's connected directly to the high-voltage bus from what I see, so unless firmware checks that all power consumers and sources add up, it will just see the reduced power use.
     
  10. FlasherZ

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

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    #10 FlasherZ, Nov 20, 2015
    Last edited: Nov 20, 2015
    At this point you've gone beyond your original question scope, which was whether Tesla would allow you to charge while towing a generator trailer (something that's been discussed in a few different threads) and whether the charge cable connected interlock could be bypassed by connecting AC cables directly to your chargers. That answer is "no". The chargers are intelligent and are told what to do by the car, which won't let it charge while driving.

    If you're interested in doing some serious hacking to make it work, then there are many options to you, but we didn't have to tell you that. You could create your own charger and integrate with the battery's HV lines (although Tesla's own BMS and sensing circuitry is likely to throw all sorts of errors on that); or, you could insert some magic module that intercepts and overrides CANbus messages sent from the car to the chargers indicating readiness and instructions for charging; or, there are others. That's rather outside the lines, though, and outside the scope of your original question, and will certainly violate warranty.

    To the best of my knowledge, no one has attempted this.
     
  11. Cyberax

    Cyberax Member

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    Ok. That's what I pretty much expected.

    People have actually done it in reverse (by tapping into the junction box under the frunk) to power non-trivial loads. Seems to work fine for them.

    That looks like the easiest way to do it.

    So nobody is crazier than I am! Mwahaha!
     
  12. deonb

    deonb Active Member

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    #12 deonb, Nov 21, 2015
    Last edited by a moderator: Mar 13, 2016
    Oh, I wouldn't say that...

     
  13. FlasherZ

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

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    Big difference. In that case you're on the uncontrolled 12V side of the DC-DC converter and a consumer of power.
     
  14. Cyberax

    Cyberax Member

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    #14 Cyberax, Nov 21, 2015
    Last edited by a moderator: Mar 13, 2016
    No, the guy I spoke during this year's TMC Connect taps into the high voltage bus. So his invertor is capable of siphoning several kilowatts from the battery (enough to power a house).

    - - - Updated - - -

    I met this guy during this year's TMC. He's also interested in a generator trailer.
     
  15. kennybobby

    kennybobby Member

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    It appears that inside the rear HVJB the HV leads to the pack, the inverter, and the output of the onboard charger are exposed to pack voltage when the pack contactors are closed, so direct injection of DC could be possible at that point. That is what the regen towing trick is basically doing.

    If you want to convert fuel to electricity it seems that a couple of options might exist such as to build a pusher-trailer or build a generator trailer with a DC rectifier bridge into the hvjb.

    Nobody even knows which processor controls the vehicle CAN bus, much less anything about the firmware, so feeding AC to the onboard charger to generate DC while moving will be difficult at this time.
     
  16. FlasherZ

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

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    You spoke to Ingineer, he was indeed showing an inverter. Good luck, let us know how your project goes.

    - - - Updated - - -

    The question is whether applying a DC voltage to the HV bus while the car is expecting only to draw it might freak out the car's software and throw all sorts of crazy errors. Then again, it might work.
     
  17. AudubonB

    AudubonB Mild-mannered Moderator Lord Vetinari*

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    As a plea to the OP, norms of propriety as well as my duties as a moderator prevent me from using the words appropriate to describe my feelings toward his project. Rather, I will tone things down several orders of magnitude and note to the OP that there are any number of ways to get to....or from... Alaska and Seattle in a Model S that do not involve this [appropriate adjectives excised] project.
     
  18. ecarfan

    ecarfan Well-Known Member

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    It seems very possible that if your Model S is damaged by doing this Tesla could decide that you have violated the terms of the warranty and the cost of any needed repairs will be on you.
    Your car, your decision.
     
  19. dsm363

    dsm363 Roadster + Sig Model S

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    This seems like a very bad idea if you ever want Tesla to touch your car again. Hope it works out.
     
  20. Cyberax

    Cyberax Member

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    I spoke with people who tried to use Tesla chargers in their own projects - it looks like a non-starter. It's difficult to hack into them (as they use liquid cooling) and they heavily depend on CAN bus to function at all.

    HVDC injection seems to be the way forward. Tesla's 400V bus is just that - a bus that connects to individual battery blocks, there are no special gateways apart from several fuses. AC and heating are connected to it directly, for example. So the most problematic point will be individual BMS systems inside the battery. They might get a wrong idea if they're charged instead of discharged while in motion.

    However, even simply offsetting some energy use by DUs and the AC system will already provide a huge range boost. And there are controllers out there capable of doing it: Electric Motor Werks, Inc. - DC Charging Systems Of course, working with 400V electricity is scary but 16kW is ultimately not a huge amount of power.

    As for warranty, I'm already close to 25k miles. I fully expect to be past 50k miles by the time I start this project.

    - - - Updated - - -

    Sure. But where's the fun in doing them? This is not a practical project (and I actually need a generator for other purposes).
     

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