Dr. Prius Says #5 31 milli-ohms; Does That Cell Need Replacing?

Discussion in 'Gen 2 Prius Technical Discussion' started by flypriguy, Sep 7, 2020.

  1. flypriguy

    flypriguy Junior Member

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    Can anyone confirm? I think it does... I've done a ton research on this site and there's an awful lot of technical battery information to digest and it gets foggy after a while. I think I got the gist of it, but wanted to see if someone would be kind enough to offer some commentary on the matter.

    I got the red triangle last night and pulled out the reader when I got home: P3000 code. The 12V battery appears to check out, I did a reading with the car off direct from under the hood (12.3v), and then from some sort of hidden tech menu accessed by turning the lights on and off 3 times. That reading was borderline at 12.0v.

    However, the Dr. Prius app shows #5 in yellow with a reading of 31milli ohms, whereas everything else is green and mostly 25 milliohms with a few 24's. I ran Dr. Prius just last month and all seemed to check out, no yellow bars.

    I cleared the code, drove around for a a while and it popped up again after about 12 miles. I'm guessing it's just not going away...lol

    Thanks!
     
  2. flypriguy

    flypriguy Junior Member

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    Wow, with all the technical folks on this site no one knows?

    Well, I guess it doesn't really matter for now anyway. Cleared the code a 2nd time, and it hasn't come back. It's been about 60 miles now...
     
  3. davecook89t

    davecook89t Senior Member

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    I'm not sure there is a definitive Internal Resistance for a particular block that will cause your car to throw a code. FWIW, 31 milli ohms does seem rather high, but what you need to focus on is the delta between the block with the lowest voltage vs. the one with the highest voltage. If that exceeds a certain level (somewhere around .3V, I believe) for a significant amount of time, you will get a code for a weak block. You would expect to see the weak block more than .3V below the typical voltage for the other blocks when the battery is discharging, or possibly more than .3V above the typical voltage of the other blocks when the battery is charging. A high IR does indicate that one of the 2 modules that make up a block is not able to store as much energy as the modules in the stronger blocks when the battery is in charge mode, although that may not be obvious when measuring its voltage. Rather than capturing the energy that is being forced into it, the weak module will dissipate some of that energy in the form of heat, and may have a higher surface charge than the stronger modules. A surface charge will quickly disappear when the module is put under load. That explains why the weak module will appear to have a higher voltage than normal when the battery is charging, but a lower voltage than normal when it is discharging. So generally the block with the high IR will contain the weak module, but that is not the standard the battery ECU uses when it decides to throw up a code.
     
  4. Prodigyplace

    Prodigyplace Senior Member

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    31 milli ohms is less than 1 ohm, almost a dead short of 0 ohms.

    The app may have stated 31 Mega ohms which would be a more reasonable high value.
     
  5. dolj

    dolj Senior Member

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    I don't really follow the reasoning here but, FWIW, Techstream displays Ω, not MΩ, the starting point being 0.019 Ω (19mΩ).
     
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  6. vvillovv

    vvillovv Senior Member

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    sorry nub here to traction pack issues and dr prius. but not grid charging.

    Are there any other noteworthy results from the dr prius battery test you might want to post?
     
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  7. flypriguy

    flypriguy Junior Member

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    Well, thank you for the commentary as I try to wrap my mind around this entirely new world! Well, it looks like I jinxed myself, today I got the red triangle, engine light, and VSC light again. The last code I got was the vague P3000 when I had Dr. Prius hooked up. Just for kicks, I took it to Autozone to see if I could get something more specific than the P3000, nope. They couldn't pull ANY code. Apparently they have to interpret whatever the handheld unit comes back with on their computers on the counter, and after entering "2005 Toyota Prius", they got nothing. Honestly, I think it was the kid behind the counter, but it was near closing time and I didn't feel like having a further discussion. Not sure if I should go to another Autozone, or just go to the local Toyota dealership. It seems to run fine, just the fan in the back is running constantly now... I've attached the last reading I got from Dr. Prius.

    To be perfectly blunt, I have no idea whether any of the Dr. Prius values are off. All I can infer is the yellow outlier is out of some sort of spec and related to the current situation.
     

    Attached Files:

  8. davecook89t

    davecook89t Senior Member

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    The screen shot you attached shows does not show a large difference between the block with the highest voltage and the one with the lowest voltage, but I really think we need a larger sample size to draw any firm conclusions. Either Torque Pro or Hybrid Assistant will allow you to log or graph the voltages of the various blocks as you drive down the road, which would tell a more complete story, as the battery charges and then discharges. If the delta never gets above .3V for any extended period of time, you may have some problem other than a weak module. At that point, you would probably need to take the cover off the battery and check for corrosion on the sensor wires or bus bars. Also, there are other possible non-hybrid battery causes for a red triangle. Check your dipstick to make sure your crankcase contains sufficient oil, use a multimeter to make sure your 12V battery is not discharged below 12 V, check the reservoir containing your inverter coolant to make sure it is circulating when the car is in Ready mode, and when the engine is cold, check your radiator to make sure it contains sufficient coolant for your ICE. It is likely that there is some problem with the HV battery, nonetheless, as indicated by the P3000 code you read. Possibly the device you are using is not seeing all of the hybrid codes. Most people who have taken their cars to Autozone to have the codes read also report that the code readers Autozone uses are similarly unable to read all of the hybrid codes.
     
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  9. flypriguy

    flypriguy Junior Member

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    Welp, I went to a Goodyear close to the house and got a more specific code, namely, p03015, which, I guess is inline with what Dr. Prius is showing.

    So, I decided to get a reconditioned battery from GreenBean and it gets installed tomorrow. My wife and I have our own vehicles and the Prius is our around town errand/dog hauler so I am comfortable with the degree of risk.
     
  10. dolj

    dolj Senior Member

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    I understand the reasons for your decision.

    With the Prius being the spare car, a concern would be that unless it is driven regularly (for 15 min or more every two to three days) the GB battery will fail sooner rather than later. Please read all of the warranty information as there is a part in it that says (paraphrased) if the car sits for some period of time without being driven, it will void the warranty. The devil is in the details, so check the details carefully.

    Good luck, I hope it lasts for as long as you need it.
     
    #10 dolj, Sep 19, 2020 at 12:55 AM
    Last edited: Sep 19, 2020 at 1:33 AM
  11. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Exactly. A used battery is the exact wrong choice for a vehicle that won't have its BMS turned on all the time. A used battery will last longest in a taxi where the car's inverter is basically on all the time. It will fail the earliest when it is a spare vehicle.

    As to your original question, 30mOhm's is not abnormal or bad. BUUUUT, if it is too different than other modules then it's a problem. Usually you're fine up until about 50mOhm to 55mOhm.
     
  12. flypriguy

    flypriguy Junior Member

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    Yes, I’ve read all the warranty nuances. The car is driven twice a day for morning and evening dog walks so it won’t be parked all that much. I did consider NewPriusBatteries, but between the wait time and DIY factor, that nixed it for me.
     
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  13. ChapmanF

    ChapmanF Senior Member

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    As close to a dead short as you can possibly get is exactly what you want for battery series resistance.

    Just think, if each block is 31 mΩ and there are 14 blocks, that's almost half an ohm total. Now put 80 amps in or out of that battery (about 16 kilowatts) and 3 kilowatts of that is going nowhere but resistive heat.

    So yes ... the internal resistance figures are specified in small units.
     
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