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gen4 Prius weird battery behavior .

Discussion in 'Gen 4 Prius Technical Discussion' started by ahab, Oct 31, 2020.

  1. ahab

    ahab New Member

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    hey everyone,
    my friend has a 2016 nimh gen4 prius (it has 250k kms or 155k miles) , some time ago he got a traction battery fault code , yesterday i had a go at the car with a vcx obd module and techstream app.

    battery error was gone and everything seemed normal , pack voltages were in good range and there were no blocks with a high voltage delta.(all around 16 something volts with some doubled that -pack 3,4,5,6,7 i believe)

    when we took the car for a 10 minute tst drive tracktion battery soc fluctuated between 64% and 40%.

    with the car in ev mode and moving back and forth a few times (less than 500m overall travel) battery went from 55% to 40% and the car stopped working in ev only mode and said "ev battery low"

    when we finished there was still no battery error in car .(i also monitored 12v battery it was above 13v all the time)

    what do you think of this behavior , im 80% sure traction battery is gone and needs to be replaced.

    or is it normal? also while driving battery did not charge past 64% and when it reached that soc it stopped charging.

    all the state of charge figures i posted are the "hybrid battery soc" section in techstream app.
     
    #1 ahab, Oct 31, 2020
    Last edited: Oct 31, 2020
  2. TMR-JWAP

    TMR-JWAP Senior Member

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    (all around 16 something volts with some doubled that -pack 3,4,5,6,7 i believe)

    Can you explain that part a bit?

    As far as I'm aware, all 14 blocks on a good condition Gen 4 should be in the 15.4-16.2 volt range when not under discharge or charge.
    If you're getting some blocks showing 30+ volts then you have a wire harness or ecu issue.

    Can you post a screenshot of the techstream data?
     
    #2 TMR-JWAP, Oct 31, 2020
  3. Elektroingenieur

    Elektroingenieur Senior Member

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    Some of the blocks have twice as many cells.
    It’s not gone until the computer says so—or at least, Toyota’s Repair Manual (more info) doesn’t provide any other criteria to decide that the HV battery has to be replaced, as long as the car drives normally and there are no battery-related diagnostic trouble codes. The car is designed for degradation of the HV battery over time.
     
    #3 Elektroingenieur, Oct 31, 2020
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  4. TMR-JWAP

    TMR-JWAP Senior Member

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    You are absolutely correct. I totally forgot the Gen 4 has only 10(?) voltage sensing points in the harness. I haven't disassembled one since February with this COVID crap going on. Starting to get old-timer memory...
     
    #4 TMR-JWAP, Nov 1, 2020
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  5. ahab

    ahab New Member

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    the thing is battery error was there but its not anymore, it might come back if i were to drive it a few more kms.
    beside the computer not giving me an error, does the capacity and the way battery behaves seem normal to you?(i personaly never had a prius so i cant tell if its normal) .
    the battery stopped charging at 60% soc and it stopped working at 40% soc (car was giving low battery warning) , we drained the battery from 50% down to 40% buy going back and forth in a parking lot 4 times maybe i don`t think we traveled more than 600 meters.
     
    #5 ahab, Nov 1, 2020
  6. alanclarkeau

    alanclarkeau Senior Member

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    You don't indicate what country you're in - not helpful, as there are many versions of PRIUS around the globe - and many different situations happening at the moment.

    1) has the car been in lockdown and not driven much at all?
    2) have you tried taking it for a "normal" drive - like 20 or 30 kms, and see if it behaves normally - or are you in lockdown which isn't allowing that?
     
    #6 alanclarkeau, Nov 1, 2020
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  7. ahab

    ahab New Member

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    the car is in Germany , we traveled a few kms in the car while i had the computer hooked up , and it was pretty much the same with the battery i could see the battery lvl go up like 3-4% with a short regenerative break and i could also see it drop like 1% /5sec under load the battery reading on the dash was all over the place as well, in span of 5 minutes i saw 2 bars and 8 bars in that screen.
    car is also giving a 5.4L/100km average fuel economy.
     
    #7 ahab, Nov 1, 2020
  8. alanclarkeau

    alanclarkeau Senior Member

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    Depending on the environment - going from 2 bars to 7 bars and back again isn't uncommon - that's what HYBRID is all about. It gains, it uses, it loses, then catches up again. On a short run like that, 5.4 l/100 is acceptable.

    I'd suggest take it for a longer run - 20km or more of mixed driving, and see what it's up to. You can do a reading of "EV Mode" from the dash display. Mine averages about 30% - depending on the environment.
     
    #8 alanclarkeau, Nov 2, 2020
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