Prime performance when EV battery is depleted

Discussion in 'Prime Main Forum (2017-Current)' started by satsuke, Apr 11, 2021.

  1. satsuke

    satsuke Junior Member

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    I'm looking at purchasing a (new) Prius prime and was wondering what the performance was like after you've used up the ~25 miles of EV range.

    I've owned 2 previous Prii and know the feeling when the traction battery is completely depleted / running on gas engine only. How does the prime handle this?

    e.g. does it retain a percentage of battery charge so the performance of the car doesn't change, or does it become a turtle like mine performs when going up Pike's Peak?

    FWIW, my previous ones were a 2006 with 245k (purchased new) and a 2012 with 221k (bought used because at $10,000 at 3 years old, couldn't pass up).
     
  2. PiPLosAngeles

    PiPLosAngeles Senior Member

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    It behaves like a "regular" Prius, just that the battery is MUCH larger (and you can drive a lot faster on battery only).
     
  3. satsuke

    satsuke Junior Member

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    So would it make more sense to _not_ drive it to depletion, at least on road trips and the like?

    Seems like it would be better gas milage over time to use electric to come up to speed and while regenerative braking and only use the gas engine for steady state driving (e.g. highway)
     
  4. jerrymildred

    jerrymildred Senior Member

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    "EV range" is fully depleted when the SOC hits 12-13%. At that point, it behaves just like a regular Prius, but still gets more miles per gallon.

    I have never heard of a Prime's battery getting much lower than that. Here's a partial screenshot from one of @john1701a's excellent videos that shows the battery SOC indicator at about the lowest point that I've ever seen mine get to.

    Screen Shot 2021-04-11 at 12.58.54 PM.jpg
     
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  5. jerrymildred

    jerrymildred Senior Member

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    Just drive it and let it amaze you. There's little, if any point in trying to game the system like in older Prii. It's often a good idea to have some EV range available on long trips for when you get off the Interstate, but not a very big deal since even in HV mode on city streets the engine is off most of the time anyway.
     
  6. Washingtonian

    Washingtonian Senior Member

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    As jerry says "Just drive it..." My son and I put over 3000 miles on mine a few weeks ago on a trip from Seattle to Denver and back. I wasn't concerned about mileage and many of the freeways had 70 and 80 mph speed limits. Of course we set the cruise control to ten over as is common in those states. I was surprised that when I checked the mileage when we got back that we averaged 45 mpg for the trip.
     
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  7. Trollbait

    Trollbait It's a D&D thing

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    Might be a good idea when going up Pike's Peak. There's a reason why GM called their charge holding mode Mountain mode.

    Not having such drives here on the East coast, I've never had my 2005 hit the point of not having battery charge for assistance.
    Maybe, but if most of your daily drives are covered by the EV range, why bother with the hassle. Well, unless you simply enjoy eking out the best efficiency.

    Little history fact. The gen1 Prius actually had a turtle mode. It was more likely to hit the point of not having enough charge in the battery for assistance than following generations, so a turtle icon would light up to alert the driver of not having full power available.
     
  8. bisco

    bisco cookie crumbler

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    i'm not even sure how far up pikes peak prime would take you before depleting a fully charged battery.
    iirc, it has the lowest ice hp of any prius
     
  9. jerrymildred

    jerrymildred Senior Member

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    Prime and regular Gen 4 have the same ICE HP according to their 2018 brochures.
    Screen Shot 2021-04-11 at 8.31.44 PM.png
     
  10. Trollbait

    Trollbait It's a D&D thing

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    The gen3 was 98hp @ 5200rpm. Like power, the curb weight is close between the gen3 and gen4. The Prime is at least 250 pounds heavier, which will have a negative impact on performance without battery assist.

    The OP likely knows where they would hit 'turtle mode' in their previous Prii. Putting the Prime into HV mode with some charge left before getting there will avoid the issue. They can also experiment to see if the gen4/Prime are as likely to reach the 'turtle mode' limit as past models.
     
  11. m8547

    m8547 Senior Member

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    I haven't taken mine up piles peak, but I've taken it up Mt. Evans. I didn't notice any issues, but at that altitude there's something like 42% less oxygen than at sea level, so any naturally aspirated engine will make about 42% less power.

    I use Hybrid Assistant to watch the engine and motor power. I've never seen the engine supply more than about 50kW (67hp) at 5000 feet, so I'm not sure if all 95hp is actually usable even if you were at sea level.

    Once the EV range is used up, the car acts like a regular Prius and automatically manages the state of charge. It will keep it between 12-14% very consistently, and only go outside that range temporarily. If the SOC drops below the target, it will automatically turn on the engine to start charging the battery. I've never encountered a situation where the engine couldn't keep up and maintain the car's desired SOC, even on sustained climbs at high altitude.

    The maximum acceleration does vary depending on state of charge, EV vs HV mode, temperature of the engine and battery, altitude, etc, but it's not a sports car, so who cares? It's always adequate for me.
     
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  12. fuzzy1

    fuzzy1 Senior Member

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    Jerry's image shows 95 HP, which should greatly exceed the ~76 HP of a Gen2, and similar amount of the Prius 'c'.
    When you initially deplete a Prime's EV mode, then it should first land in the same HV mode as a regular Prius with normal battery levels.

    You'd have to deplete it even further to get into the same territory as a depleted regular Prius. My Gen3 doesn't feel sluggish when I get down that far, not like numerous Gen2 owners described. And like Jerry, I just don't remember Prime drivers talking about getting that far down.
     
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  13. Trollbait

    Trollbait It's a D&D thing

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    In short, each subsequent Prius generation got better managing battery state of charge to avoid hitting the 'turtle mode'. There are few reports of such happening with the gen4, if any.
    With the Prime, if you do drain the charge down to such low levels, you use HV mode to save grid charge before getting to those stretches of road in the future.
     
  14. Gokhan

    Gokhan Senior Member

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    There is no such thing as the EV battery being "fully depleted." The zero-percent state-of-charge (SOC) mark, which is indicated by "--" is an arbitrary SOC chosen by Toyota. When you reach that, the SOC will fluctuate to about -15% to +3% around that, and it still behaves the same as a Prius Prime, probably a little more aggressive than a regular Prius on utilizing EV driving, albeit your HV mileage may be slightly less than a Prius Prime with more SOC in certain driving conditions because the system will have less available SOC to optimize certain driving conditions that may benefit from extended EV driving. For the same reason, Prius Prime probably gets better HV mileage than a regular Prius in more driving scenarios, owing to more flexible EV driving thanks to a larger SOC fluctuation being allowed.

    If you made the traction battery smaller and smaller, the car eventually becomes a nonhybrid car, and conversely, you can make the car a more efficient hybrid by making the traction battery larger and larger as long as the software allows that. One example would be a very long descent followed by a very long ascent. A regular Prius would quickly reach the 100% SOC during the descent and lose the remaining gravitational energy, but a Prius Prime would keep charging the traction battery through the whole descent, resulting in a much higher HV mileage.
     
    #14 Gokhan, Apr 12, 2021
    Last edited: Apr 12, 2021
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  15. bisco

    bisco cookie crumbler

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    even the pip is a turtle without sufficient battery charge
     
  16. PiPLosAngeles

    PiPLosAngeles Senior Member

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    Even on a relatively mild descent that is only 10 miles long I can usually more than "fill" the Prime's traction battery. It actually kind of worries me a bit because you're dumping ~6 kWh into the battery in under 20 minutes. That's a 3C charge rate, which can have some negative effects on lithium batteries.
     
  17. m8547

    m8547 Senior Member

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    The car will limit the charging rate and use the engine for engine braking before there are any problems with the battery. And in Japan they offer DC fast charging, so the battery must be able to handle more than the pathetic 3.3kW we get with L2 charging.
     
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  18. bisco

    bisco cookie crumbler

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    so you can turtle up pikes peak, but it's worth it because you can fill up on the way down
     
  19. fuzzy1

    fuzzy1 Senior Member

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    My Gen3 went up as far as allowed that day -- to Devil's Playground, just over a thousand feet short of the summit -- without going into any 'turtle' mode. The Prime ought not be any worse on the way up ...

    ... and vastly better on the way down, thanks to its much better regenerative capacity.
     
  20. m8547

    m8547 Senior Member

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    When I drove up Mt. Evans, I parked at the top with the EV mode range used up. From there I drove 60 miles all in EV mode. I hit close to 80% by the time I reached I-70 from the summit, and that was enough to take me all the way back to Denver.
     
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