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Prius PHV: A toe in the pond before Tesla batteries?

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by SoopahMan, Jan 19, 2011.

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  1. SoopahMan

    SoopahMan Member

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    I hate to be a party spoiler here, but is anyone else thoroughly unimpressed with the Prius PHV specs, and goals?

    EV-only range:
    13mi

    "Wouldn't a bigger battery mean greater EV range? In theory, yes. But Toyota believes many Prius drivers don't want or need the trade-off in added weight, costs and charging time."
    Toyota Prius Plug-in Hybrid Vehicle (Prius PHV)

    Sure you believe that. Or maybe you're just calling a small apartment "cozy:"

    Prius PHV battery pack: 330lbs, 13mi
    Tesla Roadster battery back: 990lbs, 250mi

    A 990lbs Prius pack would theoretically go 39mi
    A 330lbs Tesla pack would theoretically go 83mi
    Tesla's battery pack is 540% more energy dense!

    (Note that the Tesla Roadster weighs 2700lbs while the Prius PHV is around 2600lbs - very close, so weight difference isn't a major factor)

    That's not just an edge on technology, that's an outright embarrassment. No wonder Toyota engaged with Tesla with specific access to their battery technology. It sounds to me like the currently planned Prius PHV is just a wedge to get current with their competitors with whatever they can ship ASAP, until a real offering with a Tesla pack can come out.

    Another sign this is a rush job: "When pack one's battery charge is depleted, it disconnects from the circuit ... Pack one and pack two will not reengage in tandem with the main battery pack until the vehicle is plugged in and charged."

    So if you're regen-braking down a mountain, all that extra battery space you're lugging around is inaccessible to you - you'll just fill the main pack and the rest is lost to heat, just like the current model. I was really looking forward to a proper Prius PHV offering from Toyota that solved this problem. All the conversion kits suffer from this same issue because they're basically a hack, and they don't want to trifle with something so complex - that job belongs to Toyota themselves. Well, Toyota? What happened?

    In 2012 I assume the marketing will go something like, "The Prius PHV gets 13mi EV and 50mpg HV. The average commute round-trip is 40mi. On a single charge you'll get 74mpg on the average commute."

    They'll probably search for a sweet spot in these numbers:
    Graph of mpg vs distance - Prius gold, Volt blue

    Good enough. But I'm waiting for the non-hack, Tesla pack Prius.
     
    #1 SoopahMan, Jan 19, 2011
  2. Flying White Dutchman

    Flying White Dutchman Senior Member

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    the tesla can only handle 300 charge cycles and after that the energy it can hold is really decreased a lot.
    the prius can maybe handle 3000 cycles before any real big effect can be seen.

    also as the volt is really not that fuel eff. when looking at the ICE that car also needs to caarry a lot of wieght
    more battery´s wil mean lower mpg.
     
    #2 Flying White Dutchman, Jan 19, 2011
  3. SoopahMan

    SoopahMan Member

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    Are you talking 3000 cycles for the NiMH batteries in the current Prius, or the Toyota-manufactured LiIons in the PHV Prius? I do anticipate they're targeting a longer lifespan than Tesla, but the energy density difference is so stark it's almost not worth mentioning.
     
    #3 SoopahMan, Jan 19, 2011
  4. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    We have speculated before that Toyota would be implementing the same "middle-range charge-range" that they use now. That is to say, the batteries charge up to around 60% and discharge down to around 40%. Never higher and never lower. It is through this approach that many Gen1 Prius batteries still on the road show minimal loss after almost ten year of life.

    IF this is the the approach they will use, this means that as much as 75% - 80% of the battery weight is "unused". With this approach, even a small gain in distance would create a large gain in battery weight.
     
    #4 TonyPSchaefer, Jan 19, 2011
  5. SoopahMan

    SoopahMan Member

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    That charge range is in NiMH batteries, which Toyota has written numerous findings on that show an exponential gain in cycle life when keeping NiMH in that friendly range.

    Mistaking LiIon's longevity properties for NiMH is a classic mistake in mobile devices, and now those mobile devices include cars. Things that reduce the maximum charge of LiIon:

    1. Heat
    2. Time since manufacture
    3. Maintaining a high charge level
    4. Implicitly from (1), rapid discharge or charge

    Also, a high voltage applied during charging (rapid charge) reduces number of cycles before the battery dies, but increases capacity.

    This is discussed here, with fun tables that get specific:
    How to prolong lithium-based batteries

    This information leads to some very funny hypothetical scenarios for the ideal charging process for an LiIon-powered car, like:

    A. Having the customer plug it in, and letting it drain itself down to 0, then consuming just a trickle charge that runs just the safety circuits on the batteries, and puts nothing into the cells. When the customer notifies the car they'd like to drive it, it kicks on an AC and rapidly charges the batteries either to 100% or even better to some level the customer requested, all while keeping them at 0C. This would lead to very high capacity batteries late in vehicle life, but a lower number of cycles.

    B. The car's computers could track typical usage and never charge the car over the maximum % the driver uses in their daily commute. The car would wait to charge itself when plugged in until it needs to start trickle-charging to be ready for the next day. The % the car is targeting could be displayed and overridden by the user if they know they'll need more for an upcoming trip.

    Or more exotic ideas. None of them involve a small cycle range of ~20%, though.
     
    #5 SoopahMan, Jan 19, 2011
  6. usbseawolf2000

    usbseawolf2000 HSD PhD

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    PHV Prius pack: 5.6 kWh (330 lbs)
    Tesla Roadster pack: 53.0 kWh (990 lbs)

    Tesla pack has 3x the weight with ~9x the energy. So it has ~3x more energy per pound. That's with the old cells. The new high capacity cells from Panasonic (to use in Model S) would boost it additional 20-30% more energy.
     
    #6 usbseawolf2000, Jan 19, 2011
  7. cwerdna

    cwerdna Senior Member

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    The Prius PHV is NOT 2600 lbs. Neither the 3rd nor 2nd gen non-PHV Priuses are that light. 2010 Toyota Prius PHV Prototype Full Test and Video says the curb weight of the PHV is 3360 lbs.

    As for the range, it's unclear how far Toyota is allowing the PHV's pack to be drained to or charged up to. I'm also unclear (I'm sure someone knows) how far Tesla allows the Roadster's pack to go down to. I remember C&D mentioned it at one point, but can't find it at the moment.

    I did stumble across Tesla Roadster: The Mistakes We Made - Car and Driver Blog (and the related linked to entries) and found their 180 mile road trip interesting w/all sorts of range anxiety issues, partly from not charging in "range mode". Apparently, the default is not to charge in "range mode" and thus Tesla claims, C&D's driver only left w/85% charge. Hmm....

    So, ok, I think we can attribute some to unknown min and max charge levels, some to the Roadster being ~630 lbs. lighter, and maybe some to the Roadster being more efficient during these test cycles. I seriously doubt it's all in battery energy density.

    The Roadster also starts at >$100K.

    I do agree that Prius PHV not being able to regen into packs 2 or 3 after disconnection due to depletion is lame and hope it doesn't ship that way. I think everyone here on PC who got to drive one would agree.
     
    #7 cwerdna, Jan 20, 2011
  8. evnow

    evnow Active Member

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    Nissan Leaf battery back: ~600lbs, 100mi
     
    #8 evnow, Jan 20, 2011
  9. DavidA

    DavidA Prius owner since July 2009

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    What concerns me, as a prospective future PHV owner, is that the cold weather electric only performance is so much less than the 13 mile estimate. In Chicago winters, that would be a deal killer for me.
     
    #9 DavidA, Jan 20, 2011
  10. Erikon

    Erikon Active Member

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    Heh, you can always do what several Volt owners are doing to increase range, don't use the heater!:p
     
    #10 Erikon, Jan 20, 2011
  11. Flying White Dutchman

    Flying White Dutchman Senior Member

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    in the Ev world this tesla problem is well known

    i am only takling about LIon

    tesla wanted a car that was capable to do a good range of driving
    for that it used the panasonic XXX battery ( forget the name )
    a lot of them.
    it provided high energy density but at a price! low charge cycles
    but because the sports car was used normally as a sports car for fun and not a day to day driving car 300 full charge cycels would be enough.
    in the term of tesla there is also a limited warrranty
    300 full chrage cycles would be around 600 really charging or more
    so a 2 to 3 year warranty was given
    after that the capacitie would go down a lot.

    other cars use the Lion from thundersky etc etc yellow and bleu cells
    those have less capacity but over 3000 full charge cyclesand thus 16 years of live after you still have 80% thats go´s down a lot slower then the tesla battery.

    the panasonic cylinder cells used in the tesla battery pack can only do 300 full charge cycles
    after it go´s down
    a limited warranty on the battery pack is based on that 300 cylcles.


     
    #11 Flying White Dutchman, Jan 20, 2011
  12. Paradox

    Paradox Prius Enthusiast / Moderator
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    #12 Paradox, Jan 20, 2011
    2 people like this.
  13. Skoorbmax

    Skoorbmax Senior Member

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    As mentioned, Prius is much heavier than the Tesla. I don't know how its coefficient of drag compares, though.
     
    #13 Skoorbmax, Jan 20, 2011
  14. Canard

    Canard Member

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    They had to jump in somewhere. It's a sliding scale. Obviously they'll never please everyone, but if the thing had a 40-mile range, everyone would bitch that it was too expensive.

    I think they've found the right "spot".

    -Iain
     
    #14 Canard, Jan 20, 2011
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  15. GrumpyCabbie

    GrumpyCabbie Senior Member

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    Do we actually know for sure that the production version will only have a 13 mile range? Or does this range only apply to the test mules? We all know that the plug in batteries appear modular so could be added to or expanded as an option?

    Nobody from Toyota has ever dropped a hint or confirmed the exact range of the production plug in Prius, so I recon it's either top secret or undecided or both.
     
    #15 GrumpyCabbie, Jan 24, 2011
  16. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Right, the PHV prototypes have 13-14 miles EV range. It has unusually heavy battery pack. We don't know if the production version would have higher energy density or not.

    What we know is PHV Prius takes minor EV range hit in extreme weather with the preconditioning (when plugged in). If you need heat in the winter, PHV Prius' EV range reduction is less than 1 mile. Whereas, Volt takes 12 miles EV range reduction and BEV like the Leaf takes 33 miles EV range reduction.

    Below chart is in km:

    [​IMG]

    http://www.nrel.gov/vehiclesandfuels/vsa/pdfs/49252.pdf
     

    Attached Files:

    #16 usbseawolf2000, Jan 24, 2011
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  17. hill

    hill High Fiber Member

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    In addition, doesn't the tesla battery pack also take advantage of the principal of not over maximizing charge and discharge?
    Tesla (according to wiki) is sucky comparred to the Gen III. Tesla 0.35 & Gen III's are 0.25

    .
     
    #17 hill, Jan 24, 2011
  18. drash

    drash Senior Member

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    :eek:
    I'll say it comes at price. Liquid cooling is not cheap. Toyota designed their battery pack for air cooling. Huge difference here. But I would be wondering if Tesla used a lower level charging amperage like a normal 20 amp breaker would the number of cycles increase. Of course if you used that low of an amperage level it would take >14hr to recharge the Tesla battery pack. No I'd have to agree with Canard, I think Toyota hit the sweet spot with cost, reliability, and design.
     
    #18 drash, Jan 25, 2011
  19. SoopahMan

    SoopahMan Member

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    My bad on the weight - I googled it quickly and thought I'd found the right answer - clearly I did not. I'm a little surprised at how heavy the car is. Nonetheless, Tesla's batteries dwarf Toyota's proposed model in energy density, which is a big deal when you've got to carry that weight around.

    I am interested in seeing what the real timeline on the batteries ends up being on existing Teslas. Price is also a good point - if the Prius PHV comes out with an LiIon and NiMH option, I'd guess there would be a premium LiIon package that few buy and a cheaper NiMH package that a lot of people buy.

    But I still have to question whether the longer life can only be obtained by being 3x less energy dense, or as was mentioned earlier, even moreso now that Tesla's new batteries are 20-30% more energy dense - that's going to end up being about 4x as energy dense.

    In any case, it sounds like the upcoming PHV is just to have something out there until the real deal comes along with the results of this NUMMI integration and a legitimate regen setup. I'll wait.
     
    #19 SoopahMan, Jan 31, 2011
  20. Flying White Dutchman

    Flying White Dutchman Senior Member

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    qoute tesla :
    The Tesla Roadster battery pack is comprised of about 6800 of these 18650
    http://webarchive.teslamotors.com/display_data/TeslaRoadsterBatterySystem.pdf

    NCR18650 620Wh/L, 236 Wh/kg cells Panasonic 18560
    qoute again
    which can with stand about 500 charge cycles before a noticeable degradation
    Battery Charge/Discharge Cycles | Forums | Tesla Motors

    i hope i got this correct:p
     
    #20 Flying White Dutchman, Jan 31, 2011
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