Speculative : New PEV Prius only using half available LiIon capacity.

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by uart, Apr 23, 2010.

  1. uart

    uart Senior Member

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    Considering the 14 mile stated range of the new plugin-prius I was little surprised by the total weight of the battery pack (330 lb). Did this strike anyone else as perhaps a little more than they expected for just 14 miles?

    Heres some rough calculations, admittedly I don't have all the data so it's speculative. Say they only use two of the three packs for EV mode (I think thats what I've read), and also say that only 2/3 of each packs weight is actual battery (the remainder being housing etc). Well thats still 147 lb (67 kg) of LiIon battery. Now given that the energy density of modern LiIon batteries is supposedly 0.1 to 0.16 kW-hr/kg*, then taking even the lowest figure (0.1) that would still equate to about 6.7 kW-hr of EV mode.

    Also, its been estimated that in EV mode the Prius needs about 0.15 kW-hr per km, which translates to about 4.2 miles per kW-h, and I think this is a reasonably accurate figure, maybe even a little conservative. So that would mean 6.7 kW-h should give a range of about 6.7 times 4.2 equals 28 miles, double the quoted value!

    So the conclusion would be that either

    1. I've got no idea what I'm talking about (which is always possible).

    OR

    2. Toyota have somewhat over Engineered the LiIon EV system, probably going for about 70% to 75% maximum charge and about 25% to 30% minimum charge, so as to give a long service life.

    Do these numbers seem in the right ballpark?

    * Lithium-ion battery - Wikipedia, the free encyclopedia
     
    #1 uart, Apr 23, 2010
  2. fuzzy1

    fuzzy1 Senior Member

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    #2 fuzzy1, Apr 23, 2010
  3. austingreen

    austingreen Senior Member

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    Toyota's battery pack is really heavy per kwh compared to the leaf and volt. I would expect that they can really trim it down or increase the range.
     
    #3 austingreen, Apr 23, 2010
  4. Rybold

    Rybold globally warmed member

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    My iPhone battery goes below 10% before it auto-shuts down. I've had it for two years now. It still holds a full charge like when it was new. I don't understand why the Prius should be any different. Sure, I realize the RATE of change/discharge is different, but does that affect capacity?
     
    #4 Rybold, Apr 23, 2010
  5. Ads_green

    Ads_green New Member

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    You are assuming Toyota are going to use the highest density battery it can find. Aside from much higher cost, there is a real problem with heat management. These HD packs get very hot to the point it can catch fire. The tesla has a dedicated cooling system for the battery that use a similar amount of power to a domestic fridge.
     
    #5 Ads_green, Apr 23, 2010
  6. Erikon

    Erikon Active Member

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    This isn't the final configuration that we'll see in the production version, from what I understand. Remember, Toyota has always preferred battery longevity over performance and I doubt that will change any time soon!
     
    #6 Erikon, Apr 23, 2010
  7. uart

    uart Senior Member

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    What you're talking about there is more related to volumetric density and pack/module construction density rather than mass density. Given the obvious importance of weight to the vehicles overall performance I don't see any reason why they wouldn't be using at least somewhere near current "state of the art" for the mass energy density. Also, I didn't assume anywhere near the highest. The quoted range was 0.1 to 0.16 KW-h/kg and I only chose 0.1, which is about 62% of the maximum.
     
    #7 uart, Apr 23, 2010
  8. uart

    uart Senior Member

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    Yeah but that's probably still well under 1000 total cycles right. A 14 mile PEV under heavy use could go 1000 cycles in under three years, and if that was enough to wear out the battery then (in the context of the sort of reliability people would expect from modern car) that would be pretty bad.

    I don't think any of us know for certain just how good are the very latest LiIon batteries that the large PEV players are currently developing/testing, but there's lots of sources that suggest that with currently available LiIon technology that you could easily wear out a pack in under 1000 cycles if you mostly use the full capacity with deep discharge/charge cycles.
     
    #8 uart, Apr 23, 2010
  9. uart

    uart Senior Member

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    Yeah one reason might be the Prius's much smaller pack sizes, so there's relatively more of the weight taken up by the enclosure etc, compared with the Volts much larger pack.

    But I also think that Toyota is probably being really conservative on the longevity side too. I'd say they are aiming for more than 10 years out of those packs under typical usage.
     
    #9 uart, Apr 23, 2010
  10. drees

    drees Senior Member

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    You are assuming that 0% really means 0% and 100% really means 100%... It very likely does not.
     
    #10 drees, Apr 23, 2010
  11. austingreen

    austingreen Senior Member

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    Sure but 400lbs for 8kwh usage (16kwh capacity) versus 330lbs for less than 4kwh usage (5.2kwh capacity).

    IMHO panasonic ev may be behind in lithium batteries today. Since toyota is the majority owner they are going to use them. This is one of the troubles in vertical integration. Note that panasonic ev is the leader in nimh batteries so this relationship helped toyota on its current hybrids.
     
    #11 austingreen, Apr 23, 2010
  12. Prius Team

    Prius Team Toyota Marketing USA

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    Why speculate when the information is available for all to see?

    Plug-In Demo Program details (slide 32 may be of interest:p)
    -for the record, yes, our priority is longevity, not performance

    More can be found at:
    Sustainable Mobility Seminar

    Enjoy,

    Doug Coleman
    Prius Product Manager
    Toyota Motor Sales, USA
     
    #12 Prius Team, Apr 23, 2010
    1 person likes this.
  13. donee

    donee New Member

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    Hi All,

    I thought the Volt had liquid battery cooling?
     
    #13 donee, Apr 23, 2010
  14. fuzzy1

    fuzzy1 Senior Member

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    Please run that iPhone for its full cycle nearly every daily, and report back to us when it is 8 years old (42 states) or 10 years old (8 CARB states). Will the original battery still be good enough then?

    I'll bet money to the contrary.
     
    #14 fuzzy1, Apr 24, 2010
  15. usbseawolf2000

    usbseawolf2000 HSD PhD

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    About 50% is usable for gen1 Lithium pack. The capacity is rated at 5.2 kWh. I wonder if it is usable capacity or the total capacity.
     
    #15 usbseawolf2000, Apr 24, 2010
  16. aforkosh

    aforkosh Active Member

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    For the 2nd generation, we were told that the battery would not discharge below 40% of capacity nor charge to greater than 90% of its capacity. So, we were actually using only 50% of the actual capacity (90-40). Assuming that Toyota is using same boundaries for the plug-in, I think that the OP has it right.
     
    #16 aforkosh, Apr 24, 2010
  17. Erikon

    Erikon Active Member

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    Yeh, replacing a $10,000 battery pack every few years would get annoying! I'll sacrifice a few miles of range any day!:D
     
    #17 Erikon, Apr 24, 2010
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