Soc falls and rises

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Yuriy, Dec 11, 2023.

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  1. Yuriy

    Yuriy Junior Member

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    Hello everyone After installing a new battery from li-NMC cells, incomprehensible problems with the battery began, namely: During normal operation of the machine, the battery soc can sometimes drop to 1%, work a little and then rise to almost 85-90% Soc. it does not depend on the battery voltage. please help me what to do in this situation, what to watch and check, it seems to me that the battery control unit is the problem, but the algorithm of its operation is not clear
     
    #1 Yuriy, Dec 11, 2023
  2. bisco

    bisco cookie crumbler

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    not sure if those cells work with the bms properly, but aside from that, it could be the installation or other parts inside the battery case.
    any trouble codes with tech stream?
     
    #2 bisco, Dec 11, 2023
  3. jacktheripper

    jacktheripper Senior Member

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    !!! NMC lithium chemistry is too dangerous to put on a Prius !!!
    @Yuriy the up and down means the pack has been overcharged, please get it off your Prius for your safety!!!
     
    #3 jacktheripper, Dec 11, 2023
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  4. Yuriy

    Yuriy Junior Member

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    there are no mistakes, I have been driving normally since August, everything was fine, but now the frosts began and along with this problems, the mileage on a full charge of 5 km
     
    #4 Yuriy, Dec 11, 2023
  5. Yuriy

    Yuriy Junior Member

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    Why are they dangerous? do you mean ignition of lithium during overcharging or damage to the cell?
     
    #5 Yuriy, Dec 11, 2023
  6. Yuriy

    Yuriy Junior Member

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    I was driving to work today and the same situation happened, that the voltage is rising and the charge is decreasing
     
    #6 Yuriy, Dec 11, 2023
  7. Yuriy

    Yuriy Junior Member

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    li nmc perform very well in operation, do not heat up, they have a small internal resistance, about 0.6 mohm
     
    #7 Yuriy, Dec 11, 2023
  8. Yuriy

    Yuriy Junior Member

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    #8 Yuriy, Dec 12, 2023
  9. BiomedO1

    BiomedO1 Senior Member

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    faster than "normal" changes in SOC is usually one or more bad battery(s) within your pack. Since they're arranged in a serial fashion, you only see a weak block - depending on how accurate your diagnostic software is. You'll need to remove the bus bar and test each individual battery to find the weak/faulty unit(s). Your OEM diagnostic software isn't going to be much help, since it was programmed assuming nickle metal hydride batteries; the discharge/recharge curves are vastly different.

    Hope this helps.....
     
    #9 BiomedO1, Dec 12, 2023
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  10. Yuriy

    Yuriy Junior Member

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    thanks for the answer, the cells are all balanced and their voltage differs by no more than 0.3-0.4 volts if you look at the original batteries (1-14 cells)
     
    #10 Yuriy, Dec 12, 2023
  11. BiomedO1

    BiomedO1 Senior Member

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    Did you load test each individual battery? Voltages doesn't push the car amperage/watts does.
     
    #11 BiomedO1, Dec 12, 2023
  12. Yuriy

    Yuriy Junior Member

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    I checked each element for capacity, all about 6.9- 6.8 ah
     
    #12 Yuriy, Dec 12, 2023
  13. Yuriy

    Yuriy Junior Member

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    maybe someone has information on flashing the high-voltage battery control unit?
     
    #13 Yuriy, Dec 13, 2023
  14. Leonid Igaev

    Leonid Igaev New Member

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    Yuriy,we have some work of upgrade hv batteries of Honda Civic 2005-2009 and Toyota Prius Nhw 20-30 last 3 years.Earlier we applied Gsyuasa cells from Honda hybrids,now China li-ion cells 6ah.At Honda we have not problems with a battery behaviour in winter.It works normally.But with Prius we got a stable phenomena with Soc missing and graths jumping at monitor and Ice revving dangerously and so on.Such picture we monitoring not winter only but at summer weather sometimes.We supposed a capacity weakening with a cold condition,so a complicated Toyota Soc estimation algorithm is destroyed and cannot to find a real Soc meaning.Such reasons may be a low capacity with age and temperature factors .Some owners wrote here a similar examples with Nimeh Oem Prius batt.But in Siberian weather all Honda hybrids works normally.We think to add some local heater at hv battery for task desigion.Excuse my English,no practice.Thanks.
     
    #14 Leonid Igaev, Jan 6, 2025
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