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

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




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.

 

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".

 

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.