Battery running hot

Discussion in 'Gen 2 Prius Technical Discussion' started by Wrecit, Sep 17, 2021.

  1. Wrecit

    Wrecit Junior Member

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    Ok got an issue that is confusing me. Bought a refurb battery from hybrid doctor out of Virginia in late winter and it has been running like a champ. (Checking with Dr Prius app) its a 2006 prius

    On Thursday night red triangle hit the dash. I pulled over 200 yards later and checked code. The inverter pump crapped out. Towed to local dealer and $600 later baby was running like a champ. Plugged in dr prius app on Monday just to watch the pretty green meters and noticed battery bank #3 was running hot (120 plus) rolled down rear window to get more air to get reading back in the white and everything seemed ok. Temps on 3 are about 5 degrees higher than 1 and 2 but did not think anything about it. Noticed tonight that when going down larger hills and needing to ride the brake that the voltage is spiking red in Dr Prius and after going down 1 hill that is about 2 miles long (speed limit 35) temp 3 spiked at 128 degrees.

    I did pull the panel off tonight and cleaned the fan blades but the heating issue is still there down long hills (Pittsburgh Pa is all hills) the dealer put everything back together proper and I did also after cleaning the fan

    My battery temps have always been low 100s before inverter pump issue 7 days ago. Did I just junk my baby? Here are some dr prius screen shots that may help the yellow bars was brakeing Simi hard braking at 30 mph. When down hill the bars tend to be all red but was afraid to recreate for a screen shot. If it helps I will snap a picture of it tomorrow
     

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    #1 Wrecit, Sep 17, 2021
    Last edited: Sep 17, 2021
  2. Another

    Another Member

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    Is the fan running? Or just clean?
     
  3. Wrecit

    Wrecit Junior Member

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    It is running
     
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    There is nothing you can possibly have happen to the inverter that's going to cause uneven temperatures in the HV battery.

    The Gen 2 HV battery has 3 temp sensors that mount on the underside of the battery (the air outlet plenum). One mounts on the bottom of the module nearest the ECU end of the battery, one mounts near the middle module and one mounts at the far end (block 1).

    Each is just a thermistor that has a resistance change based on temperature. Quite often, I see the sensor on block 1 get damaged because that's where everyone jams there hand for lifting the battery when swapping them out, bit I don't currently remember which sensor matches to which number on that app.

    Your likely issues are a damaged sensor (usually wiring gets bent or cracked) or an actual high temp condition due to blocked air flow or inadequate airflow. Hard to tell without actually seeing the battery. There's a handful of components that are installed in the case specifically to direct airflow. Sometimes they get missed on rebuilds. There's always the chance that the actual module with the sensor mounted to it is running a bit hot.
     
  5. Wrecit

    Wrecit Junior Member

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    I was wondering if the regen braking was part of my issue. Going down long hills the pack volt will go upwards of 265 plus and blade well over 9 for as long as I have to ride the brake (10 second plus some hills (in Pittsburgh we call them hills many elsewhere call them mountain goat paths lol)
     
  6. pasadena_commut

    pasadena_commut Active Member

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    Does the battery actually get hot? If you disassemble the back of your car to gain access to the battery, then drive until the app shows it as hot, then pull over, shut down, and feel the pack (or use an IR gun to measure temps) is it actually really hot in one area?

    If the pack really is getting hot, does a dog or other source of fluff or hair ride in your vehicle? If so some of that might have gone through the fan and packed up parts of the battery to restrict air flow. Also, you said this was some sort of rebuilt battery, so who knows what the inside was like when you got it. Perhaps it would be worth opening it up just to see if there is some obvious problem inside.
     
  7. Another

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    How dirty was the fan?
     
  8. Wrecit

    Wrecit Junior Member

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    It was very dirty. I showed my wife before and after and she said oh I thought the blades were black lol
     
  9. Wrecit

    Wrecit Junior Member

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  10. punatic

    punatic New Member

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    The timing of this thread is perfect for me. I just finished assembling and installing a battery pack from Hybrid Reconditioners in Philadelphia. I have the MFD out to be replaced/repaired so I'm using the Dr Prius app to get up to speed with this car. Been driving it around here on the Big Island (we have some huge hills as well!), and observing that braking while going down one hill in particular which drops from 1000ft to around 500 in a half mile the voltage goes into the red (247 was the highest I observed), all the bars go red when I brake. Battery temps are not as high as Wrecit, more like 110 or so. But since I'm a newbie with this car I was concerned about both the overvoltage and battery heat. I know the fan is clean and working, I can hear and feel airflow, so my question is, is this normal and to be expected with charging and braking on steep hills.
     
  11. Another

    Another Member

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    Do you ever use B transmission mode on downhills instead of braking?
     
  12. mr_guy_mann

    mr_guy_mann Active Member

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    Don't be concerned about the voltage going "up into the red". The battery and hybrid ecu's will take care of things. Voltage increases during charging as the battery is "filled". If voltage gets high enough (State Of Charge is at the max value) then the car will stop charging and rely more on the friction brake.
    Your temperatures sound normal, and you mostly want to watch the voltage differential as that usually is the first indicator of most HV battery problems.

    Posted via the PriusChat mobile app.
     
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