Check Hybrid System (before and) after Grid charge

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Josh L, Oct 31, 2025 at 3:39 PM.

  1. Josh L

    Josh L New Member

    Joined:
    Mar 28, 2025
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    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    Five
    My Check Hybrid System came on twice in a week (P0A80) so I made the time to grid charge the battery. Thanks to @Abarnabe, I followed his write-up to grid charge at 350mA and light bulb discharge as I understand it. It took 4 days, so I don't think I was too far off. I moved some modules around after the final charge based on voltages after resting for an hour to try to balance the pack.

    When I drove it the first time, no issues, but the second time "Check Hybrid System" came on.

    I load tested each module with a single H7 55w 12v headlight bulb for 2 minutes and didn't see anything dramatic. Maybe the lower voltages are unacceptable?

    module, start V, V @2 min-loaded, V @2m10s-no load
    1, 8.04, 7.75, 7.84
    2, 8.03, 7.65, 7.75
    3, 8.04, 7.74, 7.81
    4, 8.04, 7.65, 7.75
    5, 8.03, 7.74, 7.81
    6, 8.02, 7.6, 7.69
    7, 8.04, 7.67, 7.8
    8, 8.04, 7.72, 7.79
    9, 8.04, 7.67, 7.74
    10, 8.04, 7.7, 7.8
    11, 8.02, 7.59, 7.69
    12, 8.04, 7.66, 7.8
    13, 8.03, 7.68, 7.76
    14, 8.04, 7.7, 7.8
    15, 8.04, 7.7, 7.81
    16, 8.04, 7.74, 7.81
    17, 8.04, 7.75, 7.81
    18, 8.03, 7.68, 7.74
    19, 8.04, 7.75, 7.82
    20, 8.03, 7.63, 7.72
    21, 8.03, 7.73, 7.83
    22, 8.04, 7.61, 7.78
    23, 8.03, 7.72, 7.82
    24, 8.05, 7.69, 7.78
    25, 8.05, 7.62, 7.82
    26, 8.03, 7.64, 7.72
    27, 8.04, 7.72, 7.82
    28, 8.06, 7.75, 7.84

    Another observation about grid charging, the charge from 101 to 238v only took about 8 hours. At 350mA, that's only 2.8AHr, seems low. I charged for an additional 6 hours to balance the cells. The charge from 84 to 238v took only 12 hours, I again let it go another 6 hours for 18 total. I didn't have the right bulbs so I used 40w bulbs in various configurations to try to get to 200, 75 and 25w, so my discharge times were inconsistent.

    I have the Dr Prius second by second recorded data for the most recent P0A80, if it would be helpful I can try to post a Google Sheets link. It was picking up my kid from school, so gently accelerating (1.34 ft/s^2, 0.04g) from 0mph to 11mph. SOC dropped from 53% to 27%. Pack voltage was 202 at 53% SOC, which seems like a mismatch.

    I would really appreciate some guidance as to next steps. Another grid charge session? A longer / higher load test to ID bad modules? Swap modules? Replace modules? Which ones? Thanks!
     
    #1 Josh L, Oct 31, 2025 at 3:39 PM
    Last edited: Oct 31, 2025 at 5:22 PM