High mileage reliability?

Discussion in 'Prime Main Forum (2017-2022)' started by Fifine, Nov 23, 2025.

  1. Fifine

    Fifine Member

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    One clarification first please: does the Prime electric battery re-charge while driving slow/downhill/cruising? Or can it be only charged off an outlet?

    From your experience, would a 2020 (or newer Gen IV) Prime have more repair and maintenance issues after 200k mi. than a regular Prius? I need help with a high mile, out of CARB warranty, used car purchase.
     
  2. BiomedO1

    BiomedO1 Senior Member

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    It works like a regular Prius, it just has a larger battery and ability to plug-in the battery. It's your choice to plug it into an outlet. The breakeven point on mine is around $0.38KwH; if your paying more than that for electricity - you won't save any fuel money.
    The key to a high mileage car is verifiable maintenance. The car is well broken-in; so odds are it's running great BUT was is it maintained per OEM specifications????? Was the oil, spark plugs, coolant changed in a timely manner. Was all the safety checks done?? Don't trust someone if they state they do all the maintenance themself. What's their background and do they know what they are doing?? That's why you want verifiable maintenance records.
    Absent the above; take the car to a third party inspection station for a through 'shake-down', usually around $100-$150. If this is a dealership or auto broker, make them give you a FREE extended warranty package, otherwise NO DEAL The price and profit margins on cars these day are crazy - so a bit of insurance for your large investment isn't out-of-line - IMHO......

    Just my 2-cents..... Good Luck....
     
    #2 BiomedO1, Nov 23, 2025
    Last edited: Nov 23, 2025
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  3. ForestBeekeeper

    ForestBeekeeper Active Member

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    Anytime the ICE is running it can be used to recharge the drive battery.
     
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  4. bisco

    bisco cookie crumbler

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    should have the same reliability, all things being equal
     
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  5. fuzzy1

    fuzzy1 Senior Member

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    Think of the Prime (or any plug-in hybrid) as having two traction batteries: a large battery that work like an ordinary plug-in EV; and a smaller battery that works like any regular Prius or other hybrid.

    Then put these two batteries together as just one slightly larger battery with two separate partitions, one for each function above. The partitioning is purely in software, not in the physical battery hardware.

    In normal conditions, the larger EV portion works the same as any other EV, and is never automatically recharged by the engine. The smaller hybrid partition is managed the same as a traditional Prius, and does automagically recharge from the engine. From a full charge, the EV partition is used first, the engine doesn't turn on until the EV portion is empty and the car switches to hybrid mode. In cruising, the computers do use the engine and short downhills and braking to keep the hybrid partition charged as needed.

    Then there are special case exceptions. There is a button you can push to force the engine to charge most of the EV partition. Though this defeats the whole fuel-savings purpose of plugging in, so should not be used for regular driving. Use it only for things like adding charge to sneak home silently at night without waking up your partner or neighbors, or not running the engine in underground parking garages, or certain downtown zones (mostly in Europe so far) that don't allow gas engines during peak hours, or emergency electric power for your house during power outages, etc.

    The car also will charge the EV partition on long mountain downhills that more than fill up the hybrid partition. Where a regular Prius fills its battery and starts spinning for ICE for engine braking, the Prime can continue sending the regenerated energy into the battery for much longer, refilling some of the EV partition too. Though I find on my similar RAV4 Prime that it runs into protection limits for battery charge rate and heating, so begins using engine braking long before the EV partition is filled.

    A separate button allows you to switch from EV mode to engine-based hybrid mode early, saving some EV battery charge for later.
     
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  6. douglasjre

    douglasjre Senior Member

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    How do I block a member who "limits who may view their full profile."?
     
  7. Fifine

    Fifine Member

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    Thank you for the excellent breakdown!
     
  8. Mendel Leisk

    Mendel Leisk MMX GEN III

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    On a phone anyway, I tapped on my avatar (top/right corner of page), in the dropdown tapped “people you ignore”:

    IMG_2436.jpeg

    then entered the member name here:

    IMG_2437.jpeg

    I was going to private message you, but encountered this:

    IMG_2439.jpeg
     
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  9. fuzzy1

    fuzzy1 Senior Member

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    From the laptop browser view, douglasjre has the exact same profile setting that he complains about for someone else in post #6:

    Screenshot 2025-11-24 105539.jpg
     
  10. rjparker

    rjparker Tu Humilde Sirviente

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    Same on ios
     
  11. bisco

    bisco cookie crumbler

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    why do people limit who can view their profile, paranoia?
     
  12. fuzzy1

    fuzzy1 Senior Member

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    Paranoia, privacy concerns on a national forum, doxxing fears, etc.
     
  13. douglasjre

    douglasjre Senior Member

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  14. rjparker

    rjparker Tu Humilde Sirviente

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  15. pasta4breakfast

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    I would expect a 2020-2022 prius prime battery to last as much if not more miles than a regular prius. I think the small battery on the regular prius will have completed more charge and discharge cycles per mile than the bigger battery on the prime. The only exception would be if someone was plugging in their vehicle multiple times a day. If you see a used high mileage prius prime with over 500 mpg on the dash, that probably means it was plugged in more than once a day. I would be more hessitant to buy if I saw that. If you see the mpg on the dash is near 50mpg, then it was probably driven mostly like a regular prius and the battery should theoretically have a lot more life left. I just recently saw one person report they sold their 2019 prius prime with 620,000 miles on it. He drove it like a regular prius and it still had the original battery. He states he sold it to his mechanic because it was starting to show symptoms of headgasket issues.The biggest problem with a prius prime out of CARB warranty is that it will cost at least $10,000 to replace the big hybrid battery with a new OEM one, so the only reasonable option is to replace it with a used or remanufactured battery that probably wont last as long as a new OEM battery.
     
    #15 pasta4breakfast, Nov 29, 2025 at 5:08 PM
    Last edited: Nov 29, 2025 at 9:04 PM
  16. Fifine

    Fifine Member

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    "over 500 mpg on the dash" - can that record be reset, like the odometer; or with lost/change of battery ?
     
  17. BiomedO1

    BiomedO1 Senior Member

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    Yes or if you hold down the button too long - don't ask me how I know this. Got distracted by a squirrel. :(:Do_O:LOL::ROFLMAO::whistle:
     
  18. pasta4breakfast

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    I didn't realize it would be so easy to reset the main display. I have experienced how easy it is to reset trip A or trip B, but I thought the total mpg wouldn't be like that. I doubt anyone would intentionally reset it though. I think most sellers and buyers would see such a high mpg as a good thing or a neutral thing.