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Prime traction battery configuration

Discussion in 'Prime Technical Discussion' started by John Clulow, Apr 8, 2018.

  1. John Clulow

    John Clulow New Member

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    I'm new and apologize if this information has been covered. We just bought a 2018 Prime Plus and I note that the traction battery is a 95 series configuration (351.5 VDC nominal). At 8.8 KWh, that would be 25Ah total pack output. So presuming they are using 18650's, do we know which one and how many are in parallel within each of the 95 serial groups? For example, I think Tesla is using Panasonic NCR18650B's at 3400 mAh each. If Toyota were using these, it would take 8 in parallel for a total of 95 X 8 = 760 cells per 8,8 KWh pack. I read they are using 5 separate packs, so that would mean each one is 19S8P and 152 18650 cells.

    By the way, this is our 4th Prius; we ordered our first one on-line in 2000 and have had a 2005 which we just traded in with 135K miles on the odometer, and a 2013 in the garage. We really like the Prime so far and I'm looking forward to participating in and learning from the forums here.
     
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  2. Elektroingenieur

    Elektroingenieur Senior Member

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    The New Car Features book, available by subscription to techinfo.toyota.com, says:

    (c) Compact, lightweight 3.7 V lithium-ion battery cells are used in order to generate high power output.
    (d) The 19 lithium-ion battery cells provided for each hybrid battery stack are connected in series in a bus bar module.
    (e) The HV battery consists of 5 hybrid battery stacks. They are connected to each other in series through bus bar modules and wiring harness.​

    There is an illustration of a cell, which is a rectangular solid with terminals on top, not a cylinder like a 18650 cell.
     
    #2 Elektroingenieur, Apr 8, 2018
    Last edited: Apr 8, 2018
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  3. John Clulow

    John Clulow New Member

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    [QUOTE="Elektroingenieur, post:

    (c) Compact, lightweight 3.7 V lithium-ion battery cells are used in order to generate high power output.
    (d) The 19 lithium-ion battery cells provided for each hybrid battery stack are connected in series in a bus bar module.
    (e) The HV battery consists of 5 hybrid battery stacks. They are connected to each other in series through bus bar modules and wiring harness.​

    There is an illustration of a cell, which is a rectangular solid with terminals on top, not a cylinder like a 18650 cell.[/QUOTE]

    Thanks. Actually I had seen this information, but obviously while 19 X 5 cells in series at nominal 3.7VDC = 351.5VDC, the typical "cell" would have a maximum Ah value of around 3.4 Ah. So that would be about 355 Wh, not 8800 Wh. I'm thinking that in the information you provided, the use of the term "cell" means each parallel group of cells, not individual 18650 cells, and that the parallel groups would have to consist of 25Ah capacity each. Another way to look at it is that Panasonic rates its NCR18650B at 12.2 Wh, so 8800 Wh / 12.2 Wh/cell = 721 cells, and that would work out to 8 cells per group in the 95S configuration or 95S8P.

    I'm looking for confirmation that that is the case and also I'd like to know which cell Toyota is using; Is it the NCR18650B or some variant of that? I don't have any particular need to know this other than curiosity :D
     
  4. bisco

    bisco cookie crumbler

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    congrats and welcome, all the best!(y)
     
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  5. fotomoto

    fotomoto Senior Member

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    Please correct me if I've got this wrong but I think Tesla was the only major player using the generic 18650 cell design. The other manufacturers are using prismatic or other type construction while Tesla has since moved to the 2170 cell for the Model 3.

    I guess another way to say it is, their common similarity is they are all different due to patents, corporate pride, tech. advances, and such.
     
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  6. John Clulow

    John Clulow New Member

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    It was my understanding that Toyota was reluctant to get into Li-ion due to safety issues but did so as a result of Tesla's experience and the elevated level of production control at Panasonic to minimize contamination etc. I'm pretty sure they had been using Panasonic's NCR18650B. Of course, Toyota had been using nickel metal hydride cells. I would be highly concerned sarfty-wise if I learned they were using prismatic batteries. I had just assumed that given the priority Toyota engineering puts on safety as well as quality, they would have built upon Tesla's and Panasonic's learning curve. But that's why I asked the question -- I'd really like to know what they are using.
     
  7. Elektroingenieur

    Elektroingenieur Senior Member

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    Iā€™m not aware of a published source for this information. The cell used in the smaller Li-ion battery pack for the fourth-generation Prius, however, is described in an SAE paper: Nagai, H., Morita, M., and Satoh, K., ā€œDevelopment of the Li-ion Battery Cell for Hybrid Vehicle,ā€ SAE Technical Paper 2016-01-1207, 2016, doi:10.4271/2016-01-1207. The paper refers to U.S. patents 8,486,564 and 8,945,768.
     
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  8. DavidA

    DavidA Prius owner since July 2009

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    This video might help. This is the disassembly of a Gen4 Prius Li-Ion pack. He does briefly discuss the differences between the hybrid-only version and the Prime's larger pack. Both Prii use what is referred to as prismatic cells vs. the Tesla cylindrical cells.

     
  9. John Clulow

    John Clulow New Member

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    Thanks, and I did watch this video in my initial research into this. It primarily covers the nickel metal hydride battery used in the standard Prius and at the very end there is a reference to the "95 cells in 5 packs of 19" but no pictures and no indication of how the term "cells" is being used (because it cannot consist of only 95 individual cell cans). Working from the available facts, I'm thinking it's likely to be five 19S8P packs connected in series, using cells like an NCR18650B. I guess Toyota is treating it as proprietary information at this time.I'm sure we'll find out eventually. So far with careful driving, we're able to get 28 miles in EV from a fully charge traction battery and it's pretty cold here in Chicagoland. Maybe results will be even better when things warm up. We absolutely love this car !!
     
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  10. John Clulow

    John Clulow New Member

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    I'd bet this would be the same cell, but I guess I'm not interested enough to pay $28 to find out :D I'll see if the patents you cite might shed any light on it. Thanks!
     
  11. CraigCSJ

    CraigCSJ Active Member

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    When I watched the above referenced video, it showed the Lion battery in the regular latest Prius and said more of the same type was used for the Prius Prime. You may want to look again.
     
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  12. bisco

    bisco cookie crumbler

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    keep in mind that toyota has been using li-on since the introduction of the 2012 plug in, and in europe before that.
    safety has not been a problem, afaik. while there have a been a few car fires reported here, idk if it has been traced back to the battery.
     
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  13. Lee Jay

    Lee Jay Senior Member

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  14. john1701a

    john1701a Prius Guru

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    Successful greenwashing will result in that assumption.

    Taking time to research will reveal they stated cost was the issue.
     
  15. Bill Norton

    Bill Norton Senior Member

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    And was a lack of a proper TMS for the pack also part of the 'cost issue'?
    (what's "Greenwashing"?)
    This is not an individual cell. This a a '6 Series' 22.2 VDC battery pack.
    A individual 25Ah - 3.8 VDC cell is not something a person buys.
    Manufacturers buy them to build a large pack and typically include a method of heating and cooling the cells as required.
    If TMS is skipped for 'cost issues', typically the Dreaded Battery Degradation shows up in harsh climates. (Leaf - Tucson)
     
    #15 Bill Norton, Apr 25, 2018
    Last edited: Apr 25, 2018
  16. Lee Jay

    Lee Jay Senior Member

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    It's 6 individual 25AH cells, in series. It's not a parallel combination of 3.4AH 18650s or similar. That was my point.
     
  17. a_gray_prius

    a_gray_prius Rare Non-Old-Blowhard Priuschat Member

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    I had been under the impression that pretty much only Tesla uses cylindrical cells - in some conversations I had with people planning EV conversions (and those who had prior experience), they noted that prismatic cells were (at that point, about a year ago) superior in terms of management and stability unless you got an entire Tesla pack and BMS. From what I've gathered, Volt cells are fairly popular.

    I am a little confused by why you would think that Toyota would have access to Tesla's (I would assume proprietary) battery development knowledge (outside of what is publicly known and what they can glean from disassembling the cars). Toyota sold off their ownership stake and (as far as I know) there isn't any technology licensing agreement in place any longer (presumably there was one in the past for the development of the RAV4 EV).
     
  18. Bill Norton

    Bill Norton Senior Member

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    Right, but also keep in mind these RC guys flog their packs. They claim to have Discharge rates of 20C, 30C maybe even higher.
    There is very little regard for life span of a pack and no thought of TMS for the pack.
    In sanctioned racing they are limited how hard they can charge them and how hot they can get the pack during charging.
     
  19. Lee Jay

    Lee Jay Senior Member

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    That's not relevant to my post. I was answering this sort of thing:

    "So presuming they are using 18650's, do we know which one and how many are in parallel within each of the 95 serial groups? For example, I think Tesla is using Panasonic NCR18650B's at 3400 mAh each."

    "the typical "cell" would have a maximum Ah value of around 3.4 Ah."

    "I'm thinking that in the information you provided, the use of the term "cell" means each parallel group of cells, not individual 18650 cells, and that the parallel groups would have to consist of 25Ah capacity each."

    I pointed out (correctly) that you can get individual 25AH cells that aren't composed of parallel groups of cells, nor are they composed of cylindrical cells.