It might be time for a new traction battery....

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by nedim, Feb 15, 2015.

  1. nedim

    nedim Junior Member

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    Well I really appreciate your time writing all this !!!

    Now I understand what you are saying. I will try to track which module is the weakest in the next coming week and hopefully I will be able to narrow it down and order a new module...
    Will replacing a bad module give the traction battery a good condition status for some time ?

    And what do you think about a grid charging ? I asked the guys at Hybrid Automotive Restore you Hybrid Battery, Don't Replace it!, they will have availability for the gen3 in the next 7-8 weeks.
     
  2. nedim

    nedim Junior Member

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    Alright, so I opened the cover and measured each of the 28 cells while SOC was 38%.
    7.47 being the highest cells on each end of the battery and 7.40 being the lowest somewhere in the middle. The ones next to it are higher by 0.1 and it increases till the last ones to 7.47.
    So do I blame that cell showing 4.70 for the fast drain I am experiencing or do I blame almost every cell?

    The orange plastic tool shows which cell I am mesuaring .
    IMG_20150218_154548754.jpg IMG_20150218_154422069.jpg IMG_20150218_154512799.jpg
     
  3. kc410

    kc410 Active Member

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    A few problems pop-up:
    1) Measuring battery voltage with no load is problematic - the cells tend to equalize their voltage rather fast.
    2) With a very good battery all 14 of the module pairs stay within 0.1V for the full range they are operated at in the Prius (40-80% SoC).
    Therefore all 28 of the individual battery modules will also track each other within 0.1V or less.

    Your voltage readings are only showing a 0.07V range between the highest to lowest modules. No meaningful results can be made with the individual battery voltages so closely matched.

    I guess the first step is to identify if you really have a bad module pair by monitoring all 14 voltages & see is you have one of the 14 that is falling lots lower than the other 13. At 60% SoC all 14 may track very well. It will be when the pack is very low (or high) that one of the 14 will start dropping lots faster than the rest. This is where Blk#max & Blk#min will help.

    A traction battery that is starting to fail will show Vmax-Vmin = 0.3V.
    This will increase as the weak cell(s) get weaker. A battery with Vmax-Vmin = 0.7V is going to be setting a code soon.
    Be safe driving when you are trying to monitor Torque :)
    If you can see 13 of the battery module pairs tracking very closely & just one falling 0.7V or more below the other 13, then you have identified two battery modules - this would be the very minimum start - after this it is just narrowing it down to one of the two modules.

    Keep in mind these readings are under load (as the battery is discharging).
    NOTE: again, when the battery SoC is in the normal range (60%) it is quite likely all 14 banks may be matched to within 0.1V.

    Another problem that creeps in is ALL 28 modules are well used & it is likely there are 2-3-4 modules that are weak. Of course just the weakest will probably show up at first. Once the weakest is replaced, the next weakest will fail etc :(

    More in the next day or so if needed - got to be up early
     
  4. Former Member 68813

    Former Member 68813 Senior Member

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    nedim,
    did you check if the bus needed cleaning while you had that opened?
     
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