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battery cell volatage advice

Discussion in 'Gen 2 Prius Main Forum' started by kindleprius, Mar 19, 2024.

  1. kindleprius

    kindleprius Junior Member

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    Hello All,
    I noticed the lights, and techstream says 'P0A80'

    And these are the voltages reported by techstream:
    Battery_2024-03-18_11-47-54.jpg


    I dismantled the pack and measured voltages with two different DMMs.
    upload_2024-3-19_13-24-15.png

    Question 1: Why does the techstream and DMM values differ?

    Question 2: Which 2-cell bank corresponds to which module? For example is V01 reported by techstream the sum of the 2 modules near the electronics or furthest away?

    Question 3: Given my uncertainty , which 2 cells should I replace (if I have to replace them at all).

    I purchased two cells from a local vendor and they read 7.8 and 7.8 V.
    DMM2 = Craftsman 82141
    DMM1 = Higher quality ennoLogic eM860T

    Thank you for your help.
     
  2. TMR-JWAP

    TMR-JWAP Senior Member

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    Easy questions!
    Your problem is in Block 12. Block 1 is the end of the battery furthest away from the ECU. Block 14 is closest to the ecu.
    Block 12 will be the 5th and 6th module from the ecu end.

    The freeze frame data you're looking at is the 'logged' information that was present when the fault triggered.
    Since that time, the battery has seen charge/dischage/etc, so the voltage can vary. Trust techstream.

    Of those two modules, one is likely good and one is likely bad. You can test them and replace only the bad one, or just replace them both and worry about which one is bad at a later time.

    All you would need to do to test it would be to place a load across it (like a 60w light bulb) while measuring the voltage. The bad one should show its voltage dropping much faster since it has one bad cell inside.
     
    Frontporch and Brian1954 like this.
  3. kindleprius

    kindleprius Junior Member

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    Thank you very much.
    Just wanted to hear some confirmation before I put the modules back in.
    Lifting the pack out seems to be the hardest part :)
     
    Brian1954 likes this.
  4. highmilesgarage

    highmilesgarage Active Member

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    nope, try squeezing the modules together and screwing/aligning them in place underneath..

    if you have time, try multiple readings every 12hrs or each day.. you might notice that some modules discharge faster than others.. that's your other candidate for replacement.
     
  5. Frontporch

    Frontporch Member

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    I don't remember an issue doing this. maybe its because I didn't do any kind of conditioning while the modules were separated.

    I saw on a hybrid service video that the blocks can be "shuffled" for better life expectancy as part of his routine maintenance. The idea here is that the center modules run the hottest and are the most likely to fail. Your issue was block 12, so it tends to disagree. I had a failed block in the center. Anyhow the maintenance is to take blocks 1-7 and put them back first and then put back blocks 8-14. Now blocks 7 and 8, that were in the center are at the ends. Hopefully I got the numbering correct.