Hybrid Battery Low SOC

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by TR738, Jan 3, 2020.

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  1. TR738

    TR738 New Member

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    I had an odd occurrence last night on my 2016 Two where the hybrid battery state of charge dropped below 20% and the drivetrain was reluctant to move the car. I stopped to pick up my mail at the end of a day of driving (about 180 mile round trip) and left the car in Park with parking brake set for the time it takes to walk to the mailbox. When I put it in Drive the car was reluctant to move up the slight driveway incline and I got a brief message that the hybrid battery was low. I've got a ScanGauge hooked up and noticed SOC was about 20% - normally never goes below 40%. I live at the top of long hill and usually the SOC is about 60% when I pull in the driveway. I had not looked at the battery status but the car was performing fine up the hill until I parked.

    The drivetrain would initially not engage with increasing engine RPM, then catch and surge ahead. Limped up the driveway and watched it for awhile in both Drive and Park and took a couple of videos. The engine RPM was hunting a bit, the hybrid diagram showed engine charging the battery but with no increase in SOC, which bottomed out around 18%. Battery temp was around 90F, more or less where it had been most of the day. Unfortunately the X-gauge codes for battery current are not working so I couldn't see that. Aux battery voltage was 14.4, charging normally.

    I did a couple of restarts and the hybrid battery finally began to charge. I shut down once it was approaching 40% and all was fine in today's driving.

    I did a Gen4 forum search on this and saw a couple of instances blamed on extended time in neutral but nothing like this. Any thoughts?

    Thanks -
     
  2. FuelMiser

    FuelMiser Senior Member

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    I'll be interested in following this thread. A couple of things you might add is how many miles on your 2016 and what accessories you were running: HVAC, Rear defroster. Things that might demand a lot of battery power. The only thing I'd guess is that somehow the computer quit charging the traction battery to protect one thing or another. Glad that a "reboot" got the battery charging again. A final thought is what is the health of your 12V aux battery? That always seems to come up when a Prius begins to act weird...
     
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  3. TR738

    TR738 New Member

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    The car has about 53000 miles. Just bought it off-lease in October, all service records included and showed no hybrid issues.

    Yes, good question about loads. It was night and dry, so only lights and low heater fan.

    Aux battery seems OK - I've been watching charging currents and voltages and they seem reasonable. I did check it during the episode and it was typical. I just looked the video I took and at the lowest 18% SOC the hybrid battery voltage was ~203-5, basically open circuit voltage for the NiMH pack so not abnormally low.

    The only other clue was in stop & go traffic after a 90 mile run** and one stop/restart. Creeping slowly in heavy traffic I noticed the engine was starting and stopping briefly and repeatedly when it typically would have stayed in EV. But sometimes the hybrid system just capriciously defies typical behavior so I didn't think much of it. My attention was outside then and also for the 5 minute drive home from there, so I didn't catch any early signs that charging was abnormal.

    ** BTW, 55.5 mpg on the ScanGauge for a 180 mile round trip, with Michelin X-Ice snow tires, temp in 40s! Mixed interstate and open 2-lane, some city at both ends. I was pretty pleased.

    - Tom
     
  4. Elektroingenieur

    Elektroingenieur Senior Member

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    I’m assuming there are no stored diagnostic trouble codes.

    Has your car had the HV ECU software update described in the original or recently-revised service bulletin T-SB-0241-17? The symptoms you describe aren’t exactly those from the bulletin, but the update should be covered under the 96-month/100,000-mile HV system component warranty, and it might be worth doing.
     
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  5. TR738

    TR738 New Member

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    No codes set or pending.

    Thank you for the heads up on the service bulletin. The symptoms do partially match. I just downloaded it and will check the status of this car.

    - Tom
     
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  6. TR738

    TR738 New Member

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    It took me a long time to follow up on this with Toyota, but the short version is that the service bulletin noted by Elektroingenieur fixed the problem. It got much worse in spring and early summer, and eventually left me partially stranded on a hill until the hybrid system decided to start charging again. Expanded symptoms are: 1 or 2 bar battery level, engine revs but does not charge the battery or accelerate the vehicle. With ScanGauge I saw SOC levels as low as ~20%. The local dealer did the software update under warranty and no problems since then.

     
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  7. TR738

    TR738 New Member

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    Forgot to say Thanks! This tip really helped!

    Tom
     
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  8. pvee

    pvee Junior Member

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    We have a 2013 Prius v with about 60,000 miles, My wife is afraid to go through a drive through restaurant because the hybrid battery goes down to a couple bars, It will recover with casual driving but it only started that this year. The Service bulletin was done last fall I think.
    Sounds like people are suggesting that the dealer won't replace it unless it completely fails.
     
  9. CooCooCaChoo

    CooCooCaChoo Active Member

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    As long as she doesn't put the car into neutral she'll be fine. The battery will take care of itself. So one of those pull-thru car washes where she has to put the car into neutral would be a no-go.

    And you can have the dealer replace it before it fails.
     
  10. 2 Pups

    2 Pups Junior Member

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    Sitting in dealership right now with this problem. My 2017 with 80k miles did it twice in the last 2 days....after going down long hills and coming to a stop, battery was at 1 bar and car seemed to be in neutral. One time I sat there for 4 minutes until battery started to charge and it went into gear. Other time only 30 seconds.

    Service bulletin (reprogram) is being worked now. Hopefully fixes the problem.

    Posted via the PriusChat mobile app.
     
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