hybrid battery pack error?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Tammy Myers, Apr 28, 2015.

  1. Tammy Myers

    Tammy Myers New Member

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    The dreaded red triangle came on my '04 Prius. When I brought it to Toyota, they said cell 13 was bad and I needed a new battery. Of course, I wasn't up for paying the $3300 they ask for a new battery. I went home and called my mechanic and he said he can just replace the bad cell, which he did. All was great for a couple weeks, when the light came back on. The diagnostics test again revealed a bad cell 13. My mechanic has my car again and said he has tested all the cells, and they are all balanced and measuring at 7.4 volts. He thinks the problem is something else. Has anyone seen this or have any suggestions? Can the battery be bad, but still testing ok individually? Thank you!
     
    #1 Tammy Myers, Apr 28, 2015
  2. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    Hi Tammy,

    Toyota's Techstream software measures the battery modules in pairs. When the dealer told you cell 13 was bad what they should have said is pair 13 of the 14 pairs has a bad module. Static voltage readings do not tell the whole story. Your mechanic needs to do a charge and discharge test. Do not let him learn at your expense. A more complete explanation is quoted below.

    Brad

     
    #2 strawbrad, Apr 28, 2015
  3. bisco

    bisco cookie crumbler

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    welcome! what he said ^^^ plus, replacing battery cells is only a short term fix. it's a complicated process to rebuild a battery pack. the more you put into it, the more you'll get out of it. suffice to say, thats why new packs are $2,000. and rebuilt packs are priced all over the lot. if you can't diy it, you kind of between a rock and a hard place.
     
    #3 bisco, Apr 28, 2015
  4. ericbecky

    ericbecky Hybrid Battery Hero

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    Just curious, what was the cost for replacement of a single cell?

    Besides just the initial voltage difference that was identified, it would have been helpful to also do some sort of overall stress test on the battery. Sometimes voltage can look good at rest, but under load/stress additional issues may present themselves.

    Replacing a cell without doing other tests is a crapshoot at best. Sometimes it works. Sometimes it doesn't.
    In your case it didn't. Hopefully your guy will give at least a small monetary credit towards a replacement pack.

    I've seen single cell replacements last as long as a year with no other intervention. Adding an HV battery charger to do some charge/discharge cycles as a preventative measure can often extend that useful life even further. But in the end, to truly fix the problem long term, the pack should be replaced.
     
    #4 ericbecky, Apr 28, 2015
    Last edited: Apr 28, 2015
  5. Tammy Myers

    Tammy Myers New Member

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    Thank you - I will have him try this too. After doing some digging, I did ask him to check the battery cooling fan too. I remembered it just starting running fairly constantly about 2 weeks ago.
     
    #5 Tammy Myers, Apr 28, 2015
  6. Tammy Myers

    Tammy Myers New Member

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    I think the single cell was only around $60...it was the 12V that was quite a bit more (which he replaced as well).
     
    #6 Tammy Myers, Apr 28, 2015
  7. bisco

    bisco cookie crumbler

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    60 bucks is cheap money for all the work of replacing a cell. at that price, it might be worthwhile to keep playing whack a mole.
     
    #7 bisco, Apr 28, 2015
    Tammy Myers likes this.
  8. ericbecky

    ericbecky Hybrid Battery Hero

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    Battery fan will run if the pack is overheating or has other issues.
     
    #8 ericbecky, Apr 28, 2015
  9. Tammy Myers

    Tammy Myers New Member

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    The guy from North Carolina is here replacing the battery with a rebuilt one. He says the wiring to the computer in the battery is all messed up and jimmy-rigged. I don't even know who could fix that!
     
    #9 Tammy Myers, May 11, 2015
  10. JC91006

    JC91006 Senior Member

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    Who is the guy from North Carolina? Did he do anything to your car while he was there?

    If your car worked for 2 weeks without problems, there shouldn't be an issue with the wiring. If anything, the bad module #13 was replaced with another not so great module. Since your mechanic replaced the module, he should have some sort of guarantee to it right?

    EricBecky can sell you some good modules, if you want to just change block #13 out again.
     
    #10 JC91006, May 11, 2015
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