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State of Charge Drops to 'Red' in 20 Minutes

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by PaulPrius2015, May 16, 2015.

  1. PaulPrius2015

    PaulPrius2015 New Member

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    A month ago I bought a 2007 Prius with 140,000 km. I notice that the state of charge drops into the 'red' bars within about 20 minutes of the car switched on, in Park with no accessories running. A mechanic connected his diagnostic computer and saw 2 cells are low. However, the mechanic informs me there is no value in replacing those cells as others are likely to go down, thereafter. Is there anything I can do to avoid having to replace the entire traction battery? The mechanic says is $3000 including labor to replace the traction battery. I am located in Vancouver, Canada.
     
    #1 PaulPrius2015, May 16, 2015
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Are any warning lights on?
    Do you notice any driveability issues such as lack of power when accelerating, unusually high engine speed, etc.?

    If your answer is no to both of those questions, I would defer any work on the traction battery at this time.

    Get Mini VCI so that you can see traction battery module pair voltages and internal resistances.
     
    #2 Patrick Wong, May 16, 2015
  3. vskid3

    vskid3 Active Member

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    The car still uses power to run the computers and inverter pump. My recommended treatment is to turn the car off when parked. ;)

    Just another Prius-specific issue that really isn't anything to worry about.
     
    #3 vskid3, May 17, 2015
  4. PaulPrius2015

    PaulPrius2015 New Member

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    Thank you for your message. I don't leave the car on when parked. The mechanic left it on to test how long it would take for the state of charge to drop significantly. I notice when driving that the gas engine comes on very soon and even with very conservative driving, I am getting 5.8 liters per 100 kilometers. Using pulse and glide and other techniques I expect to get better efficiency.
     
    #4 PaulPrius2015, May 17, 2015
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    These are not wonderful results, as that translates to ~41 mpg. I suggest that you reset the mpg gauge, and drive 50 to 100 miles on a continuous trip, on reasonably level terrain and at speeds of 60 mph (100 km/hour) or less. See what fuel economy is logged for that trip. Hopefully it will be more like 50 mpg or 4.7 l / 100 km.
     
    #5 Patrick Wong, May 17, 2015
  6. CrazyLee

    CrazyLee Member

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    #6 CrazyLee, May 17, 2015
  7. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I might be a bit confused here.
    1. Paul says that the battery runs down after sitting ON for 20 minutes.
    2. vskid says to turn it off when parked.
    3. Paul says that he doesn't leave it ON when parked.
    So how did you know to take it to the mechanic and have the battery tested?

    Off the top of my head, I don't know how long it would take for my battery to deplete when sitting ON. Perhaps 20 minutes, perhaps longer. Thinking of times when I've sat in traffic due to construction or congestion, 20 minutes sounds about right. It depends, of course, on the initial state of charge.

    All I'm getting at is this: at some point, the car sat ON and Paul to noticed that the battery depleted. Maybe this happened a few times in order to verify that it wasn't a fluke. All vskid was saying is that if the car is going to sit still for more than a few minutes, just turn it off and avoid the whole issue.
     
    #7 TonyPSchaefer, May 17, 2015
  8. SageBrush

    SageBrush Senior Member

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    Fair question. Perhaps the higher than expected fuel consumption.

    He should take Patrick's advice and run a fuel economy test under somewhat controlled conditions.

    The car consumes around 200 - 300 watts when 'on.' So in 20 minutes using 1/9th a kWh sounds ballpark. This is presuming absolutely no power accessories are operating. A new traction battery has 1.2 kWh nominal capacity, and an 8 year old car may have half. IIRC, the Prius uses 60% of available capacity. So OP's car battery may cycle from top to bottom through 360 Wh.

    Yep -- 20 minutes to 'low' sounds pretty reasonable.
     
    #8 SageBrush, May 17, 2015
    Last edited: May 17, 2015
  9. PaulPrius2015

    PaulPrius2015 New Member

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    Hi Patrick, Thank you for your message. These results are from having just come back from a 500 mile highway trip. Is there anything I can do?
     
    #9 PaulPrius2015, May 17, 2015
  10. Dino33ca

    Dino33ca Member

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    Hi Paul, I'm from Kelowna. I wouldn't worry about your hybrid battery. Like Patrick said, You should be getting better gas mileage. A 12v battery in poor condition can give you weak fuel efficiency. You might also want to check out some other potential problems that could give you poor mileage such as under inflated tires, dirty fuel injectors, spark plugs, mass air flow, air filter, etc...

    Search Results for Query: bad mileage | PriusChat
     
    #10 Dino33ca, May 17, 2015
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    To the above list, I would add:

    1. Rear brakes are dragging. Raise up the rear end of the car sufficiently so the tires are off the ground. Disengage the parking brake. Spin each tire by hand and you should find the tires spin easily.

    2. Wheel alignment is incorrect. The front toe-in adjustment should be exactly at 0 degrees (0 degrees +/- 0.2 degrees is the spec) and the rear toe-in adjustment should be slightly positive (0.3 degrees +/- 0.25 degrees is the spec).
     
    #11 Patrick Wong, May 17, 2015
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