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Traction battery module failure

Discussion in 'Gen 2 Prius Main Forum' started by fredtr, Dec 11, 2011.

  1. fredtr

    fredtr Junior Member

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    I have been posting about P3125 fault which is inhibiting ICE from starting. During this time I have been charging and also testing the traction battery so that I could continue to investigate the P3125 problem.

    This is an NHW11 venicle but the battery has the 2004+ modules, and I had been checking capacity by discharging one bank (half the modules at a time through a water heater element in a bucket of water. I could see a group of modules with capacity of only 2AH
    at a 20 amp discharge. When I disassembled these modules, they were stuck together leaking through the sides. I have tried to include a picture of one of the failed modules. The group of 6 or so modules were almost identical. This is first time I have tried to include a picture, if it doesn't show, I will try again.

    Maybe the rectangular sections are to relieve pressure, rather than explode upwards. That is where they all appeared to have leaked from. Probably one got very hot, damaged the adjacent modules.

    The capacity of this group has been about the same since I got this project car, so I don't believe I caused this charging it. I charge with a lab supply with the current typically limited to 300ma, sometimes 600ma to get it started. I have been paying attention to SOC, which is the method the Prius uses.

    Within the capacity range of the weak cells, the voltage levels kept up with the other modules. As bad as the sides of the modules look, the problem was not visible with the top of the battery case removed. I could only see the damage when I removed the modules.
     

    Attached Files:

  2. seilerts

    seilerts Battery Curmudgeon

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    Wow, that's really f****d up! I've never seen anything like it.

    The modules are designed to relieve pressure when being overcharged -- there should be a pair of black rubber hoses that runs along the tops of the cells, connecting vent ports on every other module. If left unclamped when charging, the case swells up like a balloon until the pressure is so great that vents. Yours look as if they had electrolyte leakage. It is possible that whoever had the battery before did something bad as part of their rebuild process, like clamping them in such a way that it punctured the case when they were overcharged.

    I've got six good Gen II modules, PM me and we can work something out.
     
  3. jdenenberg

    jdenenberg EE Professor

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    If you need some extra modules, I still have 6 good ones left as well.

    JeffD