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Is Gen III battery better than Gen II for high mileage?

Discussion in 'Gen 3 Prius Main Forum' started by AllenZ, Jul 23, 2014.

  1. AllenZ

    AllenZ Active Member

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    I am in the market for a used Gen III regular Prius. I know that battery in Gen III is smaller in size and weight, so energy density is greater. That's great. But I wonder if you've seen high mileage (>200K) Gen III owners experience battery performance deterioration, like someone experienced in Gen II.

    My 2004 with 220K miles only get 44mpg in this summer temp. (I drive it a little bit aggressive, use AC, and don't care much about hypermilling) I think at least partly it is due to weaker HV Battery. I can clearly feel that now it is easier for engine to rev very hard when accelerate at 50 mph. That's not the case before.

    I just bought a 2010 II, the battery feels very strong. I am going to sell the 2004 and get another Gen III. But the used price is pretty high now, at least $12K for a 100K basic car. I wonder if I should consider new one instead. Truecar.com sent me a quote of $22250 for Trim III. I guess it does not include all the other fees, such as documentation, shipping... other than tax. If you have experience with Truecar.com, please share some insight.

    Thanks!
     
  2. JC91006

    JC91006 Senior Member

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    I know that battery in Gen III is smaller in size and weight, so energy density is greater.

    I don't believe the battery to be any smaller or lighter.........In fact, many are using GenIII modules to put inside the cases of GenII cars. They fit perfectly.

    From what I understand, the GenIII can go higher speeds on battery only power vs. GenII. That's how it can get higher mpg, the engine doesn't have to kick in so early.

     
  3. bisco

    bisco cookie crumbler

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    i think gen III battery may not last as long as gen II, just from some of the threads here. but the edu recall may help with that, idk.
     
  4. JC91006

    JC91006 Senior Member

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    I think the recall is on the inverter, but idk
     
  5. bisco

    bisco cookie crumbler

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    i think so, but it might reduce battery draw according to some posters. nothing conclusive though.
     
  6. jdenenberg

    jdenenberg EE Professor

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    The Gen3 firmware runs the HV battery up to 130 amps (Gen2s were limited to 100 amps) and the modules have a smaller internal resistance than the Gen2 modules which partially justifies pushing them harder. This may account for early HV battery failures being reported in Taxi use of Gen3 Prii.

    JeffD
     
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  7. David Beale

    David Beale Senior Member

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    Yup, the GIII uses the battery more so it probably won't last quite as long, even though it's "improved". Note also that the MGs are more efficient and that also helps with mileage.
    All that being said, it's NOT the EV mode that gives high mileage! It's inefficient compared to just running from the engine. The electric portion is there to allow the "Atkinson" tuning to be practical, to allow the car to easily shut off the engine when it isn't needed and operate it in more efficient modes when it is, and to recover energy that would otherwise be lost as heat. All those "features" combine to give the fantastic mileage. Still better than any other car, in spite of what -other- manufacturers and nut cases would have you believe. ;)
     
  8. drysider

    drysider Active Member

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    The Atkinson engine is, according to Toyota engineering, responsible for only about 15% of the car's efficiency. The electrical-regeneration-battery system represents over 30%. The Synergy drive adds another 30%.
     
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  9. AllenZ

    AllenZ Active Member

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    So where is the other 15% come from? The low air drag? Lighter weight?
    I guess Toyota calculated this in a typical usage pattern, such as 50/50 highway/city.
    If you take out the battery, drive on highway at 60 mph, you will get 45 mpg;
    If you put in an Otto engine, you will get 35 maybe.
    Hybrid battery serves as energy reservoir, to help engine run at optimal speed on slightly hilly road, that will contribute some mpg increase, but I guess that's not significant amount.
     
  10. AllenZ

    AllenZ Active Member

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    Reading all your comments, guess I should stick with Gen II. High mileage Gen III is not cheap now. With my lead foot, battery failure is a high possibility in future. I just read a thread by a taxi company owner. 75% of Gen III battery failed at 150K miles. Gen II lasted to 300K no problem, just a little weaker.

    Thanks!
     
    #10 AllenZ, Jul 25, 2014
    Last edited: Jul 25, 2014
  11. GrumpyCabbie

    GrumpyCabbie Senior Member

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    My HV battery seems to be showing signs of wear at 80,000 miles. I thought it was near death at one point as it does fluctuate up and down quite quickly some times, but had the dealers run a health check and it passed and they extended the warranty by 12months/10,000 miles or until the next service. So even though my gut feeling is the battery isn't long for this world, the fact that it is once again covered by warranty helps.

    (I'm in the UK and warranties are different to yours. For a start commercial use is not excluded Hybrid Health Check | Toyota UK )
     
  12. Tony D

    Tony D Active Member

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    I asked Toyota Ireland about that extended warranty for my Gen 2 and they don't have it here! I'll probably bring mine to a Toyota dealer in Northern Ireland to get it as I don't really fancy having to take the boat over to Wales, or England to do it, although it would still be alot cheaper than replacing the battery
     
  13. GrumpyCabbie

    GrumpyCabbie Senior Member

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    Not sure whether the warranty is extended across the border as I think it's a dealer or local thing, but at only £39 it'll give you peace of mind that your battery is ok.

    Be careful with the wording they've used though. It says they check your hybrid system but the extra warranty only extends to the HV battery, not the inverter or transaxle (the expensive parts), or that's how I read it. I could be wrong and often am :)
     
  14. Tony D

    Tony D Active Member

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    Thanks for that. I work in Insurance so always read the "small print" .... there's always something there to catch you out.

    I'll check with a dealer in the North and see. It still might be worth a trip over to UK to get it done, especially with the cost of the new HV battery. It's not relevant yet, but will be next year based on my current yearly mileage
     
  15. GrumpyCabbie

    GrumpyCabbie Senior Member

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    So did I which is why I do too :)

    Makes me laugh on here sometimes with the old "a man in a pub told me..." stories of what you can and can't do. Used to hear that one in claims all the time; "this bloke told me..." or "my neighbour said it would be ok..." etc.
    :rolleyes:
     
  16. drysider

    drysider Active Member

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    The other 25% is from, as you note, low weight, good aerodynamics, etc. As I stated, the battery-regen system is a major part of the Prius efficiency. I am able to get 58+mpg on very hilly freeways in the inland NW using the battery in a pulse-and-coast kind of driving style. I stay above the speed limits, which are 65 and 70mph. That is a pretty substantial increase over 45mpg.
     
  17. AllenZ

    AllenZ Active Member

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    WOW! That's impressive!

    How do you pulse and glide at above 40 mph? Can you do it on dead flat road, such as in Chicago area?
     
  18. AllenZ

    AllenZ Active Member

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    I read from that thread that the short battery life of Gen III is caused by Toyota raise the charging/discharging current from 100 amp to 130 amp. even though internal resistance of the battery is a little better than Gen II's. They suggest be gentle for first 5-10 min warm up time, that's when charging/discharging will degrade battery the most.

    It seems like the re-gen needs to be kept shallow. Lead foot will create deep cycle which will shorten the battery life.
     
  19. drysider

    drysider Active Member

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    You can't glide above about 45mph. You can coast, but the engine will continue to turn over but not use any fuel and the EV light will not come on. It will work a lot better on flat roads- I do not get to drive on flat roads very much.
     
  20. AllenZ

    AllenZ Active Member

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    what's the indication that it is coasting? What's the range of speed that it can coasting?