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Electrical safety

Discussion in 'Gen 3 Prius Technical Discussion' started by donzoh1, Feb 20, 2019.

  1. donzoh1

    donzoh1 Active Member

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    I was told by the guy at the autoparts store today that electrocution is a real risk whe working on a hybrid. I disconnected the small 12v battery and then waited awhile before starting the cylinder head project but I'm curious about how much danger there was. My gut feeling is the highest risk would be in removing the large battery but just guessing there
     
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I would not get marriage advice from 'the guy at the autoparts store' either.

    95% of the car is 12 volt, just like any other car.

    There is a large 201 volt battery in the rear. It has relays that cut off both Positive and Negative terminals when off.

    There is a fuse you can pull to work inside the battery, but why?

    Other than the battery, the A/C compressor and the inverter use 201 volts and the Electric Motors inside the transaxle are A/C.

    This video is about the Gen 3 battery.
     
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  3. Raytheeagle

    Raytheeagle Senior Member

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    If you pull the orange safety plug, the 220 DC voltage is then immobilized ;).

    But working on the engine side of the hybrid car is not where the high voltage lies, so the risk is manageable :).

    Sounds like the auto parts store sells parts and not much else(y).
     
  4. Pluggo

    Pluggo Senior Member

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    Wonderful video. It clears up the mystery behind hybrid batteries, makes servicing and buss-bar cleaning an option for the average guy. Thanks for sharing.
     
  5. ChapmanF

    ChapmanF Senior Member

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    The inverter is up front under the hood, and contains large capacitors that store charge. There are components built in to drain that charge down to a safe value within a period of time after the relays in the battery have cut off the supply. It is good to read the manual and review what that period of time is. (I have not done so just now this morning, so I'm not going to try to say from memory.)

    All of the wires that carry high voltage are clad in orange. Sometimes, in dealing with the inverter or the A/C, you will be working with orange cables. It is good practice to pull the service plug in the battery before doing so (and wait for the capacitor drain time). There is no particularly good reason not to.

    Under fresh-from-the-factory, as-built conditions, that's belt-and-suspenders safety for you; everything up front should already be isolated by the system main relays anyway, and you pull the service plug.

    Under some non-factory-fresh conditions, voltage leakage paths can be present, and that's when you're glad to have the suspenders as well as the belt.
     
  6. donzoh1

    donzoh1 Active Member

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    Excellent information. I thought the large item in the left front under the hood was the hybrid battery but it seems it's inverter/converter? Either way, it seems like with the shielding on the plugs and cables, you'd need to be in there with a hack saw to earn a Darwin Award. A healthy level of respect for potential danger is in order but replacing a head gasket is not that dangerous. I seem to remember that the 12v battery in the back end should be disconnected and then work shouldn't begin for an hour but not sure i have that part correct.
     
  7. donzoh1

    donzoh1 Active Member

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    Thanks for that info. Where is the service plug you're talking about?
     
  8. donzoh1

    donzoh1 Active Member

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    Is it the orange one on the large high voltage one in the back? The video showed the use of high voltage protective gloves to disengage this or remove it.
     
  9. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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  10. donzoh1

    donzoh1 Active Member

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    Thanks. That's the one shown in the video. I think I read you should wait an hour after removing that before doing work on batteries and related components.
     
  11. Sr5dude

    Sr5dude Member

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  12. Grit

    Grit Senior Member

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    While removing the intake manifold during Prius meet up, my radiator fan came on while engine was OFF We thought it was the solar powering the vent while parked a dimmed car garage, my white streamers werent flapping in front of the vent ports so I know it wasn’t solar or AC fins. I did drive 2 1/2 hr for the meetup, fan was probably running with 12v batt to cool the rest down.
     
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  13. Grit

    Grit Senior Member

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    Negative, bunch of nimh battery cells.
     
  14. ChapmanF

    ChapmanF Senior Member

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    I don't think that oughtta happen when the car is off. Then again, in a Prius, it's easy to forget if the car is on but the engine is stopped. I think I'd avoid starting a manifold removal under those conditions....
     
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  15. Grit

    Grit Senior Member

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    The car was off, red immobilizer led was blinking. Some car makers program radiator fans to come on top cool down.
     
  16. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Many, but not most, cars with electric radiator fans are simply temperature activated, whether on or off, they are avoiding overheating. You can and should disconnect the 12 volt battery.
     
  17. ChapmanF

    ChapmanF Senior Member

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    What many cars do is interesting, but what the Prius does is to the point.

    All three fan relays in Gen 3 have their coils fed from the downstream of IG1 no. 1. If the car's not in IG ON, I think they ought not to be running, if everything's in as-built condition....

    ig1no1.png
     
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  18. donzoh1

    donzoh1 Active Member

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    I watched a YouTube video today showing how to remove and replace the hybrid battery cooling fan. The guy removed the rear seat and panels as required and then removed and replaced the fan. I don't believe he disconnected the 12v battery AND the service plug remained in place the whole time! This seems dangerous, even if it's only the outside of the battery that might be touched.
     
  19. jerrymildred

    jerrymildred Senior Member

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    There is no reason to pull the orange disconnect when working on the battery cooling fan. The fan is 12 volts. If 12 volts is scary, then disconnect the 12 volt battery. The traction battery has nothing to do with it.
     
  20. ChapmanF

    ChapmanF Senior Member

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    The outside of the traction battery is electrically continuous with the body of the car. If it were dangerous to touch, so would be any other metal part of the car. :)
     
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