Battery Failure: Miles vs. Years

Discussion in 'Gen 2 Prius Main Forum' started by MyBoySaturday, Oct 10, 2015.

  1. MyBoySaturday

    MyBoySaturday New Member

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    Hi! I'm considering an 05 Prius with 66k miles. I've done a lot of homework, so I know batteries almost never fail before the 10 year mark and often get 200k miles etc. But considering the car is past warranty and already has 10 years on it, would it be unreasonable to assume failure is somewhat likely in the next 2 years? Say 30% chance?
    (I paid a Toyota dealer to check it, but they did everything EXCEPT look at the hybrid battery)

    How much risk would I be taking on if I bought this car?
     
  2. JimN

    JimN Let the games begin!

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    Welcome.

    Every part has a probability of failing tomorrow and the older the battery the greater the probability of failure. The number of battery replacements is still very small when compared to the number of cars sold. If the failure rate were anywhere near the 30% you threw out you'd be able to buy a traction battery at every auto parts store.

    IMO, there's a better chance of your car being totaled in a collision and you'd have a higher risk of some failure buying other conventional cars.

    If the car is in good shape you should be OK. Relax & bank the savings.
     
  3. valde3

    valde3 Senior Member

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    Heat, mountains, or clogged fan cause more battery wear than age or mileage. And still battery has long life even when always driving up and down mountains with furry dog on hot weather. Like JimN said failure rate is still super low.
     
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  4. jadziasman

    jadziasman Prius owner emeritus

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    Depends on what you're willing to pay for the low mileage 05. Assuming that the HV battery needs to be replaced in two years, you should plan on driving it for ten. That way you recoup the cost of a new HV battery (yes, there are rebuilt ones but their reliability and longevity is highly questionable).

    It would be worth the risk if you could get it for no more than $6000. With a new HV battery that's $9000 you could end up investing. The Gen 2 has proven to be very reliable and should easily make it to and past 200K miles.

    If the seller wants a lot more than that, then it's a completely different risk. You're better off buying an 09 or a 10 or 11 Gen 3 instead. They will hold some value for a few years, the 05 won't.
     
  5. Silver bullit

    Silver bullit Right Lane Cruiser

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    Why do mountains cause more battery wear? The load of uphill driving?
     
  6. HGS

    HGS Member

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    Some people say that coasting down hill and fully charging the battery to 80% then parking it in high heat can shorten the life of battery.

    I'm not sure about other possible issues with mountains.
     
  7. bisco

    bisco cookie crumbler

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    welcome! i don't think it's unreasonable. all the best!(y)
     
  8. kinglew

    kinglew Member

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    Low. Miles mean not driven often battery fail quicker. Then one driven daily in my opinion
     
  9. valde3

    valde3 Senior Member

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    Driving on mountains causes battery charge level change between “empty” 2-bars and “full” 8-bars all the time. Like I said it can still have long life. Reason that I mentioned it and heat and battery fan clogging is that those are some reasons why you can calculate life expectancy for hv-battery. I also should have added letting Prius sit around for long time.
     
  10. houstonken

    houstonken Junior Member

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    We had battery failure at 88,000 miles and 7.8 years. Got the free replacement battery at dealer. The aftermarket replacement Prius batteries have dropped in price. Really your risk is similar buying a traditional new car in that replacement battery would be approximately the cost of a new transmission or AC system. I'd buy that Prius without hesistation.
     
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  11. Ozark Man

    Ozark Man Member

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    I have had my Prius about 5 months and they say our mountains aren't high enough to qualify as real mountains. I do go up and down some fairly steep hills though. I always use the "B" gear going down hill and it does go up to 8 bars pretty often but I have only seen it go down to 3 bars a couple times and never 2. Mostly it goes back down to 4 in town and then back up to 6.
     
  12. MyBoySaturday

    MyBoySaturday New Member

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    Thanks. I ended up buying the it! While, I feel weird paying so much for a ten year old car, I bet that this vehicle will be economical for at least 2-3 years. Battery failure rates are generally low, even out of the warranty period. Since it is in otherwise good mechanical shape and well maintained, I can't see my decision being too bad.

    There's still a few things I have to do:
    1) learn how to jump-start (or provide jumps)----since this is different on the Prius.
    2) find out if there really are problems with using custom PIDS on Torque. (the app gave me a scary warning)
    3) work out a couple contingencies for getting the hybrid system worked on (depending on the town I'm in at the time)
    4) find out how people scrap their no longer functional cars (isn't even a nonfunctional battery worth 1200?)

    I should mention, it's a change from manual; but the whole Prius driving experience is really quite engaging.
     
  13. bisco

    bisco cookie crumbler

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    congrats! recommend you don't provide jumps. a non functioning battery is worthless, except as a core return credit.
     
  14. HGS

    HGS Member

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    Jump starting another car is not something you should do with a Prius. The accessory battery is not a high amp hour type battery that ICE cars use. The inverter can't put out the amps required to jump start another car without possibly damaging it.

    Having said that, I have charged the battery in my truck when an interior light was left on. By just hooking up the jumper cables to the dead battery and letting the Prius charge the battery for about 15 minutes was enough. After disconnecting the jumper cables, the truck started just fine. The key is to only charge a low battery with jumper cables hooked up to a Prius. Don't ever hook up jumper cables and then try to start the dead car while the cables are hooked up.
     
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  15. tanglefoot

    tanglefoot Whee!

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    Congrats!

    I have high hopes for my '07 with 52k miles. It still works like new and I'll keep it as long as I can. I figure if I need to replace an HV battery, I'll still end up with a much nicer, easier to own vehicle for less cost than getting something different. I don't anticipate a failure anytime soon, though.

    I've never had to jump start the car, but I have attached a charger to the car, when I was nursing along the original 12v battery and occasionally, when the car hasn't been driven in a while. It's straight-forward. (+) terminal is inside the black plastic relax box on the driver's side of the engine compartment, under a red plastic flip-up cover. Connect (-) terminal to a grounded bolt...I use one of the bolts around the silver, rectangular inverter cover.

    I also wish it had a manual transmission, but understand that that doesn't jive with HSD. I've tried pretending that it does--it's kind of fun (but goofy). I still have my '85 Toyota truck I can row through the gears with.

    Much of the maintenance and many repairs are doable at home. I've only taken it in for recall work. Oil/filter changes, engine coolant pump change, wipers, other filters and 12v aux battery have been done at home. I'll look into doing a transaxle fluid change sometime. There are Youtube videos on how to do just about anything.
     
  16. wjtracy

    wjtracy Senior Member

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    Congrats. We don't really know how HV batt age/miles figures into life. Gotta believe internally Toyota has a great data base with lots of trends, but I presume it is proprietary.

    Lately I am wondering if there is a population of less reliable batts that fail, say 10%, and the others keep on trucking. But that's just unscientific observation about how it seems to go with posts here. Right now we seem to have a slug of 2007's going bad, next year at this time it'll be 2008's.

    Should yours fail unexpectedly, be sure to check posts here for how to contact Toyota for better deal which they give sometimes even out of warranty.

    Consumer Reports prior survey (2-3 years old now)

    [​IMG]
     
    #16 wjtracy, Nov 18, 2015
    Last edited: Nov 18, 2015
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