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2006 with 160k and repeated P0A80

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by m177, Aug 4, 2014.

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  1. Britprius

    Britprius Senior Member

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    The battery as you correctly say is only as strong as it's weakest link, and it has 168 links. (6 cells in each module, and 28 modules) Each cell has a nominal voltage of 1.2 volts in a chain of 168 giving a total voltage of 201.6 volts.
    The voltage of a cell when being discharged if drawn on a graph is nearly a strait horizontal line until it is close to fully discharged. It then drops rapidly, sometimes being described as falling of a cliff. Low capacity cells reach this point more quickly, and as the voltage falls compared with the rest suddenly lowers the voltage of the module that cell is in thoroughgoing a DTC by the battery control ECU.
    The graph below is for a 4 cell nimh battery giving a nominal voltage of 4.8 volts, but it shows how quickly the voltage falls at the discharged point.
    [​IMG]

    John (Britprius)
     
    #21 Britprius, Aug 4, 2014
    Last edited: Aug 4, 2014
    usnavystgc likes this.
  2. m177

    m177 Junior Member

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    That is really interesting. I see what you mean about it falling off the cliff. I know that the grid charger supposedly brings each cell to 100%, but I imagine that only means 100% of it's actual capacity - not necessarily it's brand new, original capacity.

    In my case, why does it take about 2 weeks for the problems with the battery to arise instead of almost immediately? Is it because as time passes, the bad cells increasingly affect the other cells?

    The car is running ok today though I did notice a 0.4 voltage difference between blocks of the highest and lowest voltages at the same time when accelerating.

    I got off work late today so I didn't have a chance to call the mechanic. And I was hoping if anything wrong is going to happen with the hv battery that it would happen tonight rather than 2 weeks from now.
     
    #22 m177, Aug 5, 2014
  3. uart

    uart Senior Member

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    No not necessarily anything else causing it. This is just one of the ways that cells age, they can lose capacity, they can increase in series resistance, and they can increase in leakage current (aka self discharge). They often do all three. You've just got some old beat up cells in that "reconditioned" pack that have too higher self discharge rate.

    What I said before. You have some cells that are self discharging, and over a period of several weeks they self discharge enough to put the pack critically out of balance.
     
    #23 uart, Aug 5, 2014
  4. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Yeah, its obvious to me that the cells were not capacity matched. That's too bad.
     
    #24 usnavystgc, Aug 5, 2014
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