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Any Prius-savvy wrenchers interested in Racing one? (SoCal)

Discussion in 'Gen 2 Prius Main Forum' started by EKIM, Jan 4, 2014.

  1. PriusTech

    PriusTech Member

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    I'm building a Lemons Chumpcar racecar.

    I thought about a Prius but it would be more expensive than what I've got and not competitive. But different strokes for different folks. You will def get attention because it's a Prius, and less pit stops because of gas mileage is an advantage. The winning LMP cars at the real Lemans race are now hybrids and Toyota has recently entered that competition venue with a hybrid racecar.

    Regarding the kill switch here's what I would do. You should try two separate kill switches. The first will be a conventional one that cuts the small (auxilliary) battery that's located at the right rear corner. This is simple and instructions are online. Just a large switch inline with the positive cable, located near the driver. Lemons has specifics on where it's supposed to be.

    The second switch will be more difficult. It is the orange switch located on the main battery. You will need to extend the wires going to it and relocate it right by the other switch. It is possible if you look at the wiring diagram for this main battery switch that it could be wired into a conventional battery cut switch. It would have to be the type that has two separate circuits.

    Regarding the push in the front end. I would try to solve that some other way. I would think you'd want more sway bar in front, not less. I would try less sway bar in rear before taking off the front. Either that or some different alignment specs. Or maybe try cutting the springs. The worst thing about 2nd gen Prius handling is the roll on cornering.

    You also might want some kind of light that comes on when braking effort goes past the regen into the actual brake pad actuation. That way you can optimize the regen.
     
  2. PriusTech

    PriusTech Member

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    double post
     
  3. Scallywag

    Scallywag Member

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    Hobbit has a good write-up of his version of this: http://techno-fandom.org/~hobbit/cars/bp/
     
  4. EKIM

    EKIM Junior Member

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    Thanks for the link on the brake light thingie. Looks like a good Prius Racecar V2.0 mod.

    There's so much for me to tackle that just simply making this thing run and get through tech inspection and be self-propelled will be enough for this one man to do (and I'm trying to build a second car and also prep a third). I've got one friend assisting with the battery balancing, but all my drivers for this race thus far aren't local so there are no "team mates" to help with any wrenching. I burned out my friends a few car builds ago.


    This first outing with the hybrid Prius will be be a success if the car completes a solid hour of driving on the track at any point during the weekend. I mean seriously, this is a 340K mile, $500 car that I can't dump any more money into beyond the required safety items.

    I appreciate that for some, wiring in a kill switch is simple, but I'm not too good with electrics. The kill switch must be able to turn off the ICE and shut off battery power through the vehicle. In the case of the prius, the ICE may actually be charging the HV system at the moment the kill switch is interrupted (more on this in a second). Typically, I use a 6-pole switch that has a resistor to protect the alternator diodes from frying if there is a sudden spike during the time between when the coil wire is "broken" and the engine stops spinning the alternator

    [​IMG]


    What concerns me is that, from my understanding, there is no 12v alternator, and the HV battery or the generator/transmission (unsure of proper terminology) are what recharge the 12v battery. It is also my understanding that once the car is running the Prius no longer needs the 12v battery to be connected and will run with it disconnected (much like any other car that will continue to run off of its alternator)?? Please correct me where I'm wrong. And if you can point me to a wiring diagram, that would certainly help me.






    I too was supposing a separate HV kill switch is best. But here's what prompts more concern from me: (Remember, I'm not so great with electricity) Everything I've encountered that's official from Toyota says that the service plug should not be handled until after 5 minutes have passed from the time the 12v battery is disconnected. And even still, that service plug should not be handled without wearing the proper safety "lineman's gloves." Have I handled the batteries and the service plug with no gloves on? Sure. But that doesn't mean I want to try and convince a chief tech inspector to heed me and pay no mind to what Toyota says.


    Anyway, so where does the potential spike of power go if someone were to accidentally trip the HV kill switch prior to tripping the 12V system switch (and the ICE just so happened to be running sending current to the batteries)? Will it backfeed and damage the car's electronics? Worse still, will it injure the person operating the switch? Someone who has attempted to help me address the HV "kill switch" suggested using a Square-D 600v 60a contactor and tying the 3 poles together to get 180A of protection...




    There must be a means to tie into the 12v relay feed for the HV system that will open the contactors in the HV pack without mucking about with the service plug. Surely there's a safety "shut down everything" feature in the event of an accident. I just need help finding that and figuring out how I can trip that, and then reverse it (meaning be able to turn the car back on and drive away again).



    I sincerely am sorry if my ignorance or lack of background in electricity, engineering, or whathaveyou frustrates those who are reading this. I respect and appreciate the depth to which the typical PriusChat members delve into their cars and painstakingly research the ins and outs of their cars over very dedicated periods of time.

    A Tremendous Thank You to those with the patience and the tolerance to reply and offer me help.
     
  5. bestmapman

    bestmapman 04, 07 ,08, 09, 10, 16, 21 Prime

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    Sounds like a fun time, good luck.
     
  6. JohnE

    JohnE New Member

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    There are HV relays inside the battery that will open for three reasons.
    1. Turning the car off
    2. HV battery module detects high voltage leak to chassis
    3. 12 volt battery is disconnected
    It would be very dangerous to run high voltage cables through the passenger compartment.
    Just opening the 12 volt battery circuit will kill the entire drivetrain.
    There are large capacitors in the inverter that absorb voltage spikes.
    If you create a large enough voltage spike I would imagine that the capacitors would be your first causality.
     
  7. EKIM

    EKIM Junior Member

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    JohnE, thank you for posting!

    I have received what may be contradictory information via a pm that suggests that the Prius will run without a 12V battery once it is running. Although cursory evidence suggest otherwise, namely the troubles that people report when their 12v battery is faulty.

    Anyway, me not knowing any better (prior to your post) it sounded reasonable that the car could continue functioning when the ICE is running and the 12v battery disconnected much like any other car that will continue to run off of of a properly functioning alternator.

    An a tangential note, the spare-parts car has proven to be "functional".

     
  8. nh7o

    nh7o Off grid since 1980

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    The car will run with no 12V battery once started properly. If the existing 12V battery has a shorted cell, then it can cause startup problems; or if the car starts, it will cause overheating of the 12V charging system. An old or sulfated battery with high internal resistance will not start the car, but if the car is jump started properly will not cause further issues. The latter case is essentially like that of having no battery at all.
     
  9. JohnE

    JohnE New Member

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    Ekim,
    I apologize I was not thinking along the lines of car already in ready mode.
    But I think opening the 12 volt battery and the DC-DC converter output circuit would kill it.
    DC-DC converter takes the place of the alternator and is located in the inverter above the transmission.
    I am assuming there is a rule of how far away from the battery the kill switch must be but the best place to kill power would be at the engine compartment junction block. Both 12 volt battery and converter hook up at the junction block and you could cut all 12 volt power there. That should shut down everything and it's all low voltage.
    Should be easy to test out now that you have a running prius(y) .
     
  10. miscrms

    miscrms Plug Envious Member

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    This page (linked below) has some good pics of the point where the 12v dc from the inverter comes into the fuse box about half way down the page. I think that's exactly where you want to insert your kill switch. This should kill everything, ICE, HV and 12V power. As far as I know the HV systems requires 12V to keep the contactors closed between the battery and the drive system. I would just try and avoid hitting the kill switch while the HV system is under load, doing this repeatedly will likely fry the contactors. They are meant to open and close with no current flow, and can suffer arc damage when current is flowing. This should all still do its job if you have to shut down under load in an emergency, in which case the potential damage to the contactors is just an accepted risk of dealing with the emergency.

    Inverter on 12v battery | PriusChat
     
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  11. Fubar1764

    Fubar1764 Member

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    ekim,
    Remember that your $500 budget is NET. Meaning, all the parts that you strip off that are sold can count towards your go fast parts. Pick up a couple of spare engines and trannies (not part of the $500 budget). We always had at least one in race trim ready to swap. The Prius tranny swap should be pretty easy.
    Strip all the glazing. I wouldn't replace the glass with plexi since you're not going to get to and sustain a speed where it matters that much. Tailgate gets pitched (and sold). You also don't need the rear doors. The seats are heavy. You should be able to replace the seat as "safety equipment" for your racing harness. R compound tires will help dramatically, but they also increase your cost of consumables. I'd go so far as to strip the front and rear bumper covers and sell them as well. You can easily bump your build by $1.5k just by stripping parts off the car and selling them.
    Have you ever run LeMons before? The Prius isn't going to be competitive with the Miatas (nothing is, really). In fact, the Prius isn't going to be competitive at all! BUT, if you race it a couple of times, Jay will find some way to get you a trophy - he's just that kinda guy. A fellow Lotus buddy ran a Pinto station wagon with a slushbox and FINISHED! All stock. He made zero mods beyond safety and tires. He ran it and had fun. Remember that LeMons is an event; Chumpcar is competitive. As for competitive, consider an enduro for the Prius. Driven conservatively, the Prius should do reasonably well just from the lack of pits.
    Random thoughts:
    30" pizza boxes make excellent signs for the driver, e.g. "Pit Now"
    You can also get the pizza joint to give you the boxes and feed your team as a "sponsor," which makes your team 1) even more hilarious, and 2) the envy of the paddock.
    Practice the driver swap. Almost every "penalty" will require a driver swap.
    Buy a fast flow gas can for refueling.

    Post pictures!
    Cheers!
    Jack
     
  12. sdtundra

    sdtundra Senior Member

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    What do you still need assistance with? I have limited time but have some contacts within Toyota as well as access to electrical engineers to bounce ideas off of. Also, what time frame are you looking at? I am in East SD btw
     
  13. EKIM

    EKIM Junior Member

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    Uh, pretty much "everything" but what that means is whatever someone can and wants to render help with, I'll take it. Even if it's just a phone consult or better still an in-person overview of "here's what I see you're facing... good luck." I've got simple tasks like helping reinstall the interior trim. I'll have to figure out how to use the new cable and software I just bought so I can read and address the issues that pop up in the computer. The brake pump runs constantly so at minimum I'll need to know which "brain" to swap out as a first step toward diagnosis. There's an engine misfire as well. Going to change the trans fluid, see if I have VSC and if so how I might be able to disable it (unplug stuff?).

    The biggest issue however is still the need to wire in a safety kill switch that doesn't fry the car or the operator. From all of the help I've gotten here and from talking with others, it seems wiring in an aftermarket Square D contactor is likely more detrimental than helpful. The best bet is to figure out how to trip the contactors in the battery case utilizing the 12v system, and also cut the 12V power flow to ensure no power is flowing anywhere, not even the dash lights.

    I'd also like to figure out how to tap in to the harness so I can double the stock "ready" light in the console with a roof- or dash-mounted amber light so that safety workers know that when the light is illuminated the car may be "energized", and when it's not on it is safe. I think the worst case scenario for me as a car owner is that the car is disabled, the driver is in need of emergency help, and the workers are afraid to approach the car to render assistance. Ultimately, that's the goal of a "kill switch", to render the car more safe in the event of an emergency, so that occupants and emergency crew can proceed with what they need to do.

    I was thinking that if there is a simple way to tap into one of the collision sensors (isn't there one mounted right there on the side of the inverter?) then we could disable the vehicle safely using the car's stock, built-in safety systems that Toyota engineers spent years and gajillions of yen figuring out.

    And thanks for posting. FWIW, work is being undertaken in both Escondido and Ramona.
     
  14. Tony D

    Tony D Active Member

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    Looking like an exciting project! Best of luck