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Battery crack

Discussion in 'Prius PHEV Plug-In Modifications' started by olov, Aug 8, 2011.

  1. olov

    olov New Member

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    Part of enginer pack almost 1 year old failed during driving this spring with chemical smell and had no time to look until now. Smelly goo thru the cracks, suggestions how to clean it? Other cell pairs measure ok and I replaced this with my last spare. Could it be frozen or "normal" fail? Olov
    [​IMG]
     
    #1 olov, Aug 8, 2011
  2. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    The picture is way too small to see anything usefull. Use those electrons and upload a higher resolution image.

    Normally the only failures for LiFePO4 batteries is diminished charge/discharge capacity. If you have a physical failure, it is definitely abnormal. Cracks usually develop because there was too much current flow or too much temperature delta. There are other possibilities but those are the big ones.
     
    #2 2k1Toaster, Aug 8, 2011
  3. olov

    olov New Member

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    Attached Files:

    #3 olov, Aug 11, 2011
  4. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Ok, well the 2 obvious ones I can now tell by looking at the image:

    1) The cracks were caused from the inside coming outside. It was not physical pressure or dropping them or something puncturing them or anything like that where damage happened tothe battery.

    2) The discolouration of the plastic housing suggests either the phosphate leaked or it was damaged by heat. Put some gloves on and run your fingers over the discoloured parts. Is it smooth or is it bumpy/groovy?

    My 1st order diagnosis would be the charger did not stop those cells from overcharging. It looks like a standard overcharge to thermal runaway to exothermic reaction scenario. LiFePO4's are very strict when it comes to charging algorithms and the Enginer system is... not.
     
    #4 2k1Toaster, Aug 11, 2011
  5. olov

    olov New Member

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    Battery pack had not been out of the car for at least 8 months.
    These are of a version that have at least over voltage protection hardware devices on each cell maybe a glorified zener diode or so and they (normally) work. I seen that at a friends where the heat and discolouration is placed in another place due to that function. Surfaces are rugged but still smooth as the fluid is still there. It was charged outside with cabinheater on and it was pretty cold here at times, mostly every night it rested in a heated garage w/o charging. My experience of the event was that after starting after a outside charging that had no signs of fail I did drive a few km and then suddenly it smelled intense so I had to open the door window and the battery pack operation ceased. Could they have frozen? Do the fluid expand when frozen? Is the evaporated stuff not so good to inhale? Any suggestion on removing the fluid on the bottom of the box, it is there and stinking slightly? Thank´s for the input. Olov

    Seems the normal event is this:
    http://www.mpoweruk.com/lithium_failures.htm

    evaporating gas seem to be flammable so opening window may be wise.

    maybe low temp lower the limits when it happens, as these are built from 3 cylindrical cells they must first have "disassembled rapidly" internally that may have been earlier.

    Seems fluid is PEG Polyethyeleneglycol or similar I guess like antifreeze so I will not drink it.
    [ame]http://en.wikipedia.org/wiki/LiPo[/ame]
    [ame]http://en.wikipedia.org/wiki/Polyethylene_glycol[/ame]
     
    #5 olov, Aug 11, 2011
  6. coulomb

    coulomb Junior Member

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    LiFePO4 does not like being charged below freezing (zero Celsius). Is it possible that despite the cabin heater being on, the cells might have frozen while charging? If you live in a particularly cold place and sometimes need to charge outside below freezing, you might have to consider Thunder Sky / Winston / whatever they are called now; they have Yttrium in them which seems to allow them to be charged below freezing without damage. As far as I know, these are the only LiFeYPO4 cells you can get; all others are LiFePO4.
    I believe it's lithium hexafluoride, and I don't believe it's good for your health. So get rid of it without getting it on your skin too much, and try to avoid breathing it.
     
    #6 coulomb, Aug 13, 2011
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