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2020 ESh questions about the battery…

Discussion in 'Lexus Hybrids and EVs' started by ESh, Mar 26, 2023.

  1. ESh

    ESh New Member

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    Hello.
    Last year I bought a CPO 2020 Lexus ESh with 20000 miles. The car runs and drives great but there is one problem: the battery does not like rapid charging downhill, it will “overheat” and then the ICE runs all the time, especially when the battery is near full/full. It will regen normally but the ICE turns on at slightest throttle.
    The fan filter is new, the fan runs (0-6 when commanded by Techstream or Dr. Prius. Sadly, I cannot hear the fan spinning when on AUTO at all.


    Here are some videos that I took today with Dr. Prius:





    Any advice?
     
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    Have you driven other Toyota hybrids? Usually with HSD, the car will run the engine to discharge the battery if you charge it up to the top via regen on a downhill section. Toyota is quite conservative and keeps the battery around 60% true SOC for longevity.
     
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  3. ESh

    ESh New Member

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    Tideland Prius, thank your for your reply.
    I drove many Toyotas hybrid, I also have a 2022 RAV4 hybrid which acts in similar way but they are some big differences.
    First, the RAV has Li-Ion battery and the Lexus has Ni-MH battery.

    What are the differences between them? On the same downhill both cars charge the batteries at 100%. Both of them then start spinning the ICE via MG1 to "burn" the excess energy that regen brakes produce. The difference is that the RAV turns off the ICE as soon as get to the flat surface (battery full) but the Lexus keeps spinning the it until the 8th bar disappears. Also, the battery on the RAV never overheats, but on the Lexus the battery overheats and the car would not drive on EV alone but the ICE comes on at the slightest press on the throttle.
    Also, the problem is that the cooling fan on the Lexus never come on, I didn't hear it running on it's own.

    Then, there's another issue. On normal driving conditions, the RAV turns off the ICE every single time I go off throttle. On the Lexus that is not the case, most of the time the ICE keeps on spinning (MG1 spins it, no fuel used) for 5, 10, even for 15 seconds after I go off throttle which means that it drains the battery.
     
  4. bisco

    bisco cookie crumbler

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  5. drash

    drash Senior Member

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    I'd agree with @bisco , its pretty normal for the Lexus NiMH. Is there a warning that comes on that tells you the battery overheats? Those battery temps look pretty typical to me because I've monitored my PiP and Prime. The battery in my NXh rarely gets to 10 bars, mostly 9 on really long hills and I have two motors that do regeneration because its AWD. I use the heck out of the paddle shifters to slow down which provides added regeneration. You are correct that Lexus hates seeing the battery full. Typically Lexus is very aggressive in actions to protect the battery and spins the heck out of the fans in the battery compartment but you can't hear it because they are exhaust fans to the outside which are surprisingly loud outside. It also uses the extra energy to recharge the brake pumps. Doesn't take much for the engine to come on when the battery is close to full and when its low. I'm curious now. I'll have to monitor the NXh to see what the actions are and my battery is older. Haven't monitored it in a long time.
     
  6. drash

    drash Senior Member

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    Ok looked through some OBD data collected on my NX 300h which has the same battery as your 2020 ESh. Yeah just starting off, the fans are going over 40% and hit 60% after warming up, but you never hear them. Temps were in the 50s today. BTW I'm using OBD Fusion which I import into a spreadsheet. Haven't specified the battery temps yet. Probably rerun them after I change out the 12V which is dying. Expensive big AGM battery. :eek: A lot bigger than the 2nd Gen Prius or the PiP or the Prime.
     
  7. ESh

    ESh New Member

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    There’s no warning. Just the fact that it will drive on ICE only until the battery temp goes down.
    I understand that the MG1 has to spin the ICE so it will not overcharge the battery, but there two things that I don’t like here:

    1. The temperature rises but the fan does not spin. I checked it on Techstream. And yes, I can hear it from the second speed (total 6). i have only one fan under the right rear passenger.
    2. Why it spins the ICE when I release the gas pedal (temp OK, battery level OK)?



    Also, when I use the paddle shifters, let say I go downhill and I keep it on 2, the regeneration is much lower, I don’t need to break as much and it will keep the battery from getting full fast and overheating.
     
  8. ESh

    ESh New Member

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    I also have the OBD Fusion (paid version). Can you attach the file? Thanks.
     
  9. drash

    drash Senior Member

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    I uploaded it as an Excel file. Wouldn't let me upload a CSV. Oh and I only monitored 1 cooling fan, it has 2.
     

    Attached Files:

  10. drash

    drash Senior Member

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    I've noticed it stops increasing regeneration after I go down to 3 on the paddle shifters. Kind of stays at one level. Have not tried Sport or Eco mode either. Odd you have a fan under the seat, my fan is not located under the seat. They're further down in the battery compartment on each side of the battery pulling air from the battery to the outside. I have a screen behind the grate that I vacuum. It's located under the driver side rear passenger seat.
     
  11. ESh

    ESh New Member

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    Thanks for the file. Is it possible to read the battery temperaturw with OBD fusion? I don’t see that option.


    Your Lexus has two fans because the battery is devided which means it has much better cooling.
     
  12. drash

    drash Senior Member

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    You must be looking at Dashboards. You have to go under Settings -> Preferences -> Logging -> Select PIDs -> (the Toyota, Lexus, Scion selection should show up. If not you'll have to purchase them) -> Hybrid Control (under which there must be 350 or so). If need to purchase or restore purchase, you have to go under Settings -> Purchase Extras -> (at this point you may have to hit Restore Purchases just above Help at the bottom) -> Toyota, Lexus, Scion -> Toyota 2020 Enhanced Diagnostics

    You may have to purchase the 2020 enhanced diagnostics for $14.99 which I did a long time ago for 2018 and 2017 or all of them for $74.99.
     
  13. ESh

    ESh New Member

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    I’m thinking about adding an additional battery fan on other side of the battery which will suck the air through the battery/filter and push it outside the car. It would run all the time when the car is on/READY and most likely it would run at full blast, especially during summer time.
    I not sure which hybrid battery fan can push/suck more air? Any ideas?
     
  14. drash

    drash Senior Member

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    Seems like a trip to the junk yard is in order. See if you can snarf a centrifugal fan off of a battery of a junked Prius or other Toy or Lexus hybrid. They are the most efficient for pushing air.
     
  15. ESh

    ESh New Member

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    Thanks for your answer.
    I think I should get one out of Prius II. Is it true that the Prius II fan has 2 wires and it would work on full if they’re connected to + and -?
     
  16. drash

    drash Senior Member

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    True, but you could connect it to the 12 cigarette outlet which only comes on when the car is in ready mode.
     
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