Question about hybrid battery failure.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by brccli, Jan 7, 2015.

  1. brccli

    brccli Junior Member

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    We have a 2005 Prius with about 155,000 miles on it. It seems that battery is starting to go a bit. The mileage is down under 40 mpg (used to always be high 40s or low 50s on my commute) and the battery meter indicates that it charges and discharges more quickly than it did in its youth. I am the primary driver and am content to drive it until absolute failure. My wife is an occasional driver, but is a bit concerned about what might happen if the battery finally quits while she's driving. I've only read about people experiencing failure during startup, not while in motion. Can this happen? How does the car respond?
     
    #1 brccli, Jan 7, 2015
  2. nh7o

    nh7o Off grid since 1980

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    Yes, it happens while driving. What you will hear is a lot of fan noise from the vent at the side of the rear seat. The SOC indicator will jump from low to high and back quickly. The car will eventually go into limp mode, where the engine will rev higher than usual while accelerating. You can drive the car on level road at constant speed, as that does not use the battery. But lots of stop and go will be trouble, as you may not be able to accelerate as fast as the people behind you would like.
     
    #2 nh7o, Jan 7, 2015
  3. alekska

    alekska Active Member

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    Mileage is always down in winter. Use of the heater and longer time it takes for engine to warm-up all decrease the mileage. Also, the cold Hybrid battery has less capacity, therefore charges and discharges faster. There is nothing to worry about, unless computer throws a code. You can check the condition of the Hybrid battery by looking at the module voltages (actually, a difference in voltage between modules), for that you will need an OBD2 adapter and a smartphone or pad.
    The small (12v, non-hybrid) battery is the one that causes the start-up issues.

    As mentioned above, car is still drivable if hybrid battery dies. Just less power.

    - Alex
     
    #3 alekska, Jan 7, 2015
  4. DenToyPri05

    DenToyPri05 Junior Member

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    From what I've just experienced, I'd get the 12v battery checked and replaced if indicated. I don't think it's worth the chance of getting stranded or having your day interrupted by something that could be easily prevented.
     
    #4 DenToyPri05, Jan 7, 2015
    Last edited: Jan 7, 2015
  5. brccli

    brccli Junior Member

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    Thanks for the replies. I am actually not too concerned about anything happening very soon. I'm also not too concerned about getting stranded because this car pretty much only travels to and from a limited set of locations. The only reason that the issue is worrisome is that it's pretty mountainous around here and I wouldn't want a potential failure to be dangerous. I'd like to know that we would at least be able to get safely to the side of the road, even uphill.
     
    #5 brccli, Jan 8, 2015
  6. DenToyPri05

    DenToyPri05 Junior Member

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    Alex, just curious...for you, how much more down is mileage? ("more down"...Is that even grammatically legal?)
     
    #6 DenToyPri05, Jan 8, 2015
    Last edited: Jan 8, 2015
  7. alekska

    alekska Active Member

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    I have short drives and bad traffic (Atlanta), In summer I have usually around 43-44 mpg. In winter (if you call that in Atlanta) it goes to ~ 38-40. I do run heater/AC.
    I have my grille almost fully blocked in winter.

    At the same time, when I drive at ~55mph on highway in summer or in winter I can get ~50-55 mpg on long stretches.

    P.S. Car has 160k miles on odo now
    - Alex
     
    #7 alekska, Jan 8, 2015
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