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transient problem: engine not charging battery

Discussion in 'Gen 2 Prius Main Forum' started by A.J. Tarnas, Oct 10, 2022.

  1. A.J. Tarnas

    A.J. Tarnas Junior Member

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    i just experienced something odd for the first time. i drove about 5 miles, 40-50mph, and during that time the motor did not seem to recharge the battery at all. rolling hily terrain, would expect some charging. battery got down to purple and seemed to not be contributing to the forward motion of the car anymore. parked.

    then drove two more miles to a different destination. same situation. motor really had to rev to get up to speed, 40mph. braking while coasting downhill charged the battery one bar. parked.

    got out the carista obd-ii bluetooth dongle and dr prius on iphone, started car again to drive 10 miles home. no issue now. car behaves normally. no anomalies.

    anyone have any ideas? if this keeps happening i will probably be able to get better diagnostics on the anomaly. no codes presently. but if anyone recognizes this pattern i'd like to get a head start on figuring it out.

    context:

    240k miles, bought used in aug 2020 with 190k miles on it, appears to be the original HV battery. this 2007 prius lived most of its life in mild sunny oakland CA, last two years has lived near brutally hot joshua tree CA. 85f-90f today. this car is generally getting 43mpg, most of my driving is 30-55mph 10-30miles. the car has a prius offroad liftkit and slightly larger tires on the original aluminum alloys.

    attached are two snapshots from dr prius at during normal driving -- braking vs maintaining speed.
     

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    #1 A.J. Tarnas, Oct 10, 2022
    Last edited: Oct 10, 2022
  2. bisco

    bisco cookie crumbler

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    any noise from the battery cooling fan?
     
    #2 bisco, Oct 10, 2022
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  3. PriusCamper

    PriusCamper Senior Member

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    You got warning lights on the dash for that experience? What happened when you checked for error codes? Basically your symptoms is what happens when dash lights come on, error codes get stored and computer shuts down the hybrid system because there's a problem, which was why the engine was working so hard.
     
    #3 PriusCamper, Oct 10, 2022
  4. A.J. Tarnas

    A.J. Tarnas Junior Member

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    no unusual dash lights. no codes readable through dr prius. yes, i did hear that the hv battery fan was on.
     
    #4 A.J. Tarnas, Oct 11, 2022
  5. TMR-JWAP

    TMR-JWAP Senior Member

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    You may want to see if your app displays the upper charge and discharge limits. (I know hybrid assistant does). It would be interesting to see these values when you have that issue.
     
    #5 TMR-JWAP, Oct 11, 2022
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  6. A.J. Tarnas

    A.J. Tarnas Junior Member

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    from what i can tell, dr prius doesn't log max and min charge amps. visually / from memory i can say i've seen charging as high as 31amps recently. i'll have to find my spare android phone and try hybrid assistant.
     
    #6 A.J. Tarnas, Oct 11, 2022
  7. TMR-JWAP

    TMR-JWAP Senior Member

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    The car will assign a max charge and max discharge limit for the battery depending on whatever factors Toyota deemed important. (like temperature, SOC, etc). This limit is typically ~25kw but can be reduced greatly during very hot or cold conditions, or low/high current soc.
     
    #7 TMR-JWAP, Oct 11, 2022
  8. A.J. Tarnas

    A.J. Tarnas Junior Member

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    in this case, 31a at 247v would be 7.7kw.
     

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    #8 A.J. Tarnas, Oct 11, 2022
  9. bisco

    bisco cookie crumbler

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    i would clean the fan and intake. if that doesn't fix it, open the battery and look for more dirt and corrosion
     
    #9 bisco, Oct 11, 2022
  10. TMR-JWAP

    TMR-JWAP Senior Member

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    I've never experimented to accurately determine what temperature triggers a cutback in the limits, but I wonder if that 119F had anything to do with it. Certainly, owners out west and deep south-west would have input or complaints about that. Seems likely a car interior would hit 120 frequently in some areas. IDK off the top of my head at what point the battery throws a temperature code, or if even does. Actually, I don't think it codes for any temp unless it thinks it senses a thermistor failure.
     
    #10 TMR-JWAP, Oct 11, 2022
    Last edited: Oct 11, 2022
  11. A.J. Tarnas

    A.J. Tarnas Junior Member

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    fan zone is clean. battery enclosure and connections appear to be clean.no visible corrosion.

    battery temp is unlikely to be the sole problem. this was a relatively mild day by my standards. air temps above 110f are normal where i live from may through september. this prius has driven in such conditions for 2 full summers now.
     
    #11 A.J. Tarnas, Oct 11, 2022
    Last edited: Oct 11, 2022
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  12. bisco

    bisco cookie crumbler

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    perhaps just the battery getting weak, but not outside code parameters yet. might trigger charging shutdown based on battery data.
     
    #12 bisco, Oct 11, 2022
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