Help! - rebuilt HV battery, no voltage out

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by LKasdorf, Jan 21, 2020.

  1. LKasdorf

    LKasdorf Junior Member

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    Vehicle:
    2007 Prius
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    II
    This is my first time rebuilding a prius battery pack. I get 217v between the anode and cathode of the pack, as I should. However, these large cables from the pack go through black plastic terminal blocks (fuses? relays?) before connecting to the car. I get 0v across these terminals that the car connects to.

    What are these devices that the 2 large cables connect to on the output of the HJV battery?

    All of the dash lights are on, including red triangle. I've connected Dr Prius and Hybrid assistant apps and have seen the graph of battery voltages. It is showing #12 quite low, even though a voltmeter check of the cells doesn't show one being low. I've installed it without the cover, so I can check the cells.

    I'm sure the answer to this is out there and is very basic, and I'm looking.
     
    #1 LKasdorf, Jan 21, 2020
    Last edited: Jan 21, 2020
  2. TMR-JWAP

    TMR-JWAP Senior Member

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    Those are the two main relays that will close to apply HV to the inverter. They won't close until you press the power button with your foot on the brake.

    If you tried that, and it didn't work, then you most likely did not fully install the safety interlock plug on the battery. There are three (3) steps.
    1. Insert plug into the socket. This alone will put full voltage at the battery side of the relays.
    2. Rotate the handle upward toward the 12 oclock position
    3. Press the handle straight down toward the 6 oclock position and the handle will slide down about 1/2 inch. This is the part that inserts the shorting wire across the interlock contacts. to let the car know the interlock switch is fully installed. If you don't perform this step, the relays will never get the permissive to close.
    As for #12 being low, what are the actual voltage readings shown by the app?
    You may have damaged the voltage sensor tab for that block during removal/installation. It happens fairly often when the old sensor harness is disassembled to clean the busbars, etc. The crimp where the small wire attaches to the tab is very fragile. Doesn't take much to crack it.

    You should also inspect the sensor harness orange electrical connector where it plugs into the ECU, the plug and socket are very susceptible to corrosion damage, which will cause faulty voltage readings.
     
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  3. LKasdorf

    LKasdorf Junior Member

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    II
    Ok- it is all working now. Thanks for the reply.

    I just kept trying to get the ODB to connect to my phone, turning car off, restarting, and eventually the car started up normally! Then, I tried driving a bit, there was a jerk and it stopped.
    At this point I realized that I had never bolted the battery down into the car. So I did that, and tried some more. At some point, the car booted up normally.
    Red triangle was still on, but I was able to drive. I connected to ODB with dr prius app and now, section 8 was quite low.
    I took it down the road, and did several rapid accel/decel cycles at the instruction of the Dr Prius app battery test. Then I did the battery life test where you put in drive and press brake and accel pedal.
    Going back to the battery voltage monitor, I saw that #8 was coming up to nearly match the others. I drove it down the road a bit, and shortly, I was seeing a near perfect chart- almost exactly the same voltage for all sections!
    So- that is the current state- nearly perfect.
    I don't know what I was doing wrong. After I posted, I did remove the orange fuse module, did a continuity test on the fuse, and re-installed.

    The ways of the Prius are very strange...
     
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  4. TMR-JWAP

    TMR-JWAP Senior Member

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    Just be aware the voltages you were looking at that were near perfect may have been while the battery was under "charge" condition. That charge current tends to make them very even, and will often make a weak block read slightly higher than the others.
    Drive it a time or two, then one morning, don't put your foot on the brake and press the power button twice to put the car in ig-on condition. This will allow you to read the HV battery voltages after they've settled all night, without the engine starting or putting charge current into the battery. It will give you a pretty accurate condition of the battery block voltages.
     
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