"Toshiba engineers have cracked the Holy Grail of electric vehicle batteries..."

Discussion in 'General' started by Carcus, Oct 20, 2017.

  1. Trollbait

    Trollbait Well-Known Member

    20 years at 15,000 miles a year is 300k miles. The US average annual miles, per person, is just over 13,000 miles.
  2. RedylC94

    RedylC94 Well-Known Member

    Which was my point. If the battery lasts that long, or 54 years of average driving, that's longer than nearly all conventional cars last, so battery life would seemingly be a non-issue.
  3. Carcus

    Carcus Well-Known Member

    “According to the YouTuber, Tesla has been talking to CATL for around a year to adopt the new cell format and chemistry in its entry-level MIC (Made In China) Model 3. The Chinese Standard Range will have a range of more than 155 mi (250 km) in order to be eligible for EV subsidies, will be much cheaper than the current derivatives for sale, and may also last longer, due to the lithium iron phosphate (LFP) chemistry.”

    Confirmed: MIC Tesla Model 3 Will Have Prismatic LFP Cells

    /everything old is new again?
    Last edited: Feb 24, 2020
  4. Trollbait

    Trollbait Well-Known Member

    Toyota went to prismatic cells in the Prius because they dissipated heat better, allowing just a fan for the NiMH pack. Hybrids using cylinderical cells had a loop off the A/C.

    Tesla's choice here isn't about the cell's format. It is because they are cheap and local, which means no strain on their supply of 21700 cells for the rest of the world. They might also learn something from CATL on moduless packaging. This short range pack is going to as large as the long range one. LiFe is lower energy density.
  5. litesong

    litesong litesong

    Nah! A lot of degradation occurs, just because the battery exists. It appears a lot of rich people are putting a lot of miles on their battery packs, knowing that the packs are not going to be "a rich person's idea of functional" in 10 (or less?) or 12 years. People talkin' 54 years of use are blowing smoke.
  6. litesong

    litesong litesong

    But, average western U.S. drivers drive many thousands of miles more than east coast drivers, the east coast driving the average well downward. & a large percentage of westerners, drive much more than the average westerner. Since I retired, I drive more than when I worked, thought about 22,000+ miles. I did a few minor calculations, & now think I'm driving as much as 30,000 miles per year.
    Last edited: Feb 25, 2020
  7. Carcus

    Carcus Well-Known Member

  8. S Keith

    S Keith Well-Known Member

    One really should apply a minimum standard to a reference. A little critical thinking goes a long way. Don't mistake marketing materials for technical data.

    One need look no farther than the battery longevity of the Honda "D" cells vs. the Toyota prismatic cells. It took me 14 core packs to build 3 decent ones for the 06-08 HCH2. 14 Prius packs will yield 10-13 packs depending on acceptance standards.

    Here's a reference:

    Do a little research and discover that Honda has been sued on almost every NiMH hybrid it has made due to battery issues. The 09-11 HCH avoided it because they upped everybody's warranty to the CA 10 yr/150K mile warranty regardless of state.

    And Trollbait, the ONLY cylindrical cell hybrid battery that uses an A/C loop is the FEH/MMH, and they stopped that after 2010. No Honda NiMH pack EVER did, and I'm 90% sure the 11-12 Fusion didn't either. In short, A/C cooled NiMH cylindrical HEV batteries are a small percentage of the total.
    litesong and Trollbait like this.
  9. Carcus

    Carcus Well-Known Member

    ALL OTHER FACTORS BEING EQUAL—- cylindrical cells are naturally going to be easier to keep cool— because the cells aren’t packed so tight — a trade off with energy density . Wouldn’t you agree?
  10. S Keith

    S Keith Well-Known Member

    First, an apology is in order for being sloppy. When a webpage compares two things showing only the advantage of "A" vs. the disadvantage of "B" (vs. the advantages and disadvantages of both), the information is clearly biased and can't be taken out of context or even necessarily regarded as accurate. Raise your standards.

    If I were completely ignorant of the factors involved, I would agree with you since you seem to supply a logical statement. Unfortunately, the logical statement doesn't include multiple factors that influence cooling. Since I am not ignorant of the concepts of fluid flow and heat transfer, I am unable to agree with you. It's like saying, "Look at the sky! Barely a cloud in the sky! What a perfect, beautiful day. It's going to be sunny and beautiful all day, don't you agree?" while ignoring the thunderhead behind you moving your way.

    I refer you to NASA to impart a basic understanding of fluid flow around a cylinder (complete with pictures):


    Look at the picture/animation. Can you see how there is no consistent contact with the backside? How effective is cooling on the surfaces on the back side of the cylinder? Not at all.

    Again, one need to only look towards the specifics:

    Minimum cross section thickness
    Prismatic cell = 0.75"
    "D" cell = 1.3"

    Running the specific numbers between Honda six cell sticks and Prius 6 cell prismatic modules shows the prismatic module has a 15% LARGER surface area to volume ratio, and all exposed surfaces experience equivalent airflow.

    "D" cell:
    Thicker cross section = harder to cool
    Terrible airflow characteristics (less surface area receiving consistent cooling flow) = harder to cool
    Higher volume to surface area ratio = harder to cool

    I have personally watch a cylindrical cell battery go from 130°F to 150°F AFTER being parked. That tells you there's a dramatic difference between the center and surface of a "D" cell. The most I've ever seen a prismatic battery go up in the same scenario is 8°F.

    The vast majority of Honda "D" cell hybrid battery failures have been due to poor thermal management. The FEH and the HCH2 share the EXACT same Sanyo cells; however, the FEH is one of the best packs ever made while the 09-11 HCH is the WORST pack ever made with a 3-4 year failure rate of 30-32% (per the CR article). What's the difference? Thermal management. Honda did a shit job removing the flow baffles and Ford kept the baffles, added an evaporator to chill the cooling air flow and aggressively tries to keep the pack below 90°F. With those improvements, the FEH battery is only mildly better than a non A/C cooled Prius battery.

    Use of cylindrical cells requires a robust default design (low mΩ and low %C utilization) with superior thermal management to overcome their inherent disadvantages.
    RedylC94, Trollbait and litesong like this.
  11. Trollbait

    Trollbait Well-Known Member

    Tesla's cooling system for the cylinderical cells has a contact point with each individual cell. Most of the others have it per module.
  12. Carcus

    Carcus Well-Known Member

    I’m so so very very sorry for my poor choice of reference. I will try to do better in the future. Please accept my apology .

    “Because of the design of cylindrical Li batteries, they also tend to radiate heat (and thus control their own temperature) more easily than their prismatic counterparts. Because of the way that prismatic cells are all placed together, this certainly works to increase the capacity, but it also leaves room for a higher probability of design inconsistency and short circuiting. The larger size of the prismatic cell may also be attractive in certain situations, but it also minimizes the chances that such a battery could be used in a heavily automated environment. That larger cell size also creates perhaps the biggest disadvantage for prismatic batteries: the increased capacity makes it far more difficult for the battery management system to properly regulate heat and prevent the battery itself from overcharging.”

  13. Trollbait

    Trollbait Well-Known Member

    Your source sells battery packs made with cylindrical cells. Perhaps they are better for what those packs are used for, or it could be because they are cheaper.

    Toyota has been using prismatic NiMH cells in hybrids since they took the Prius out of Japan. The Prime is using prismatic Li-ion cells made by Sanyo. Using more expensive cells that shed heat worse in an air cooled pack isn't something I see Toyota engineers doing.
  14. Carcus

    Carcus Well-Known Member

    They design/engineer with different chemistries AND form for many different companies.

    / thanks for dawg piling on, but you missed the pile
  15. Trollbait

    Trollbait Well-Known Member

    Any of them a car company? Build any battery packs bigger than that drone?

    Small portable packs for equipment that use passive cooling is a different environment than a traction pack with forced cooling for a car.

    Perhaps Nissan should have used cylindrical cells in the Leaf. Toyota did for their Chinese plug ins.
    In this case, it is about, "...helps Toyota deal with the challenge of securing high-quality batteries, but also should boost Panasonic's profit margins..."
  16. S Keith

    S Keith Well-Known Member

    Again, critical thinking is in order. Conveniently ignoring anything beyond a single cell, that MAY be true. However, what happens when you put two cells in close proximity to one another? 3? 4? 84? 2,976? 4,416? 7,104?

    Where does the heat go? Yep. Into the adjacent cell. How do you keep them from cooking themselves? Prayer? Nah.

    Cylindrical cells need a robust and well designed cooling system due to their inherent poor cooling flow characteristics.

    Again... as a reminder... I've personally observed a "widely" spaced "more easily radiated" cylindrical cell Prius pack INCREASE 20°F AFTER being parked vs. 8°F for a prismatic pack. Also likely worth pointing out the the cylindrical cells are installed in a pack DESIGNED for prismatic modules. Since the prismatic modules cool more efficiently due to uniform airflow across the facing surfaces, they do not get as hot as cylindrical cells which have about 60% less surface area being used to cool a thicker section. The cooling system needs to be modified to adequately cool the cylindrical cells. Additionally, they need hardware added to optimize the flow, and they need the fan speed responding about 15°F sooner than the prismatic modules to compensate for the much larger difference between the cell core temp and surface temp.

    A BEV is a system, not a single component. Details matter.
  17. Carcus

    Carcus Well-Known Member

    Yah, I understand all that ... what you're saying is better stated here:

    ""The problem with a big battery cell is that the thermal pathway in a worst case scenario is very long. Say, if there is a hot spot in a battery, can it get its heat out? If it is deep in a cell, it can't do that. It is also so hard to thermally condition the cells. The life of the pack will be dependent on not the average temperature but the worst temperature at any point in any cell. So you want to really even the temperature out. That is why Tesla is fan of having lots of small cells and then actively cooling each cell to keep the temperature even and make sure that if hot spots does develop, there is a very short pathway to the cooling system and it can take care of it. And you also want to make sure that it is passive propagation proof i.e even if the active cooling system fails, and you get a thermal runaway in a cell, that thermal runaway then can't cascade into neighbouring cells and you (avoid) the thermal domino-effect. It's not super complicated. So.. If you have big cells, you want big gaps and ideally you don't want big cells. "

    So for this conversation I would add that you don't want big, high energy prismatic cells all smashed together in prismatic fashion so that you somewhat 'naturally' DON'T have a pathway to get the heat out.
    That is my understanding of why I have seen it stated several times by people that ought to know that a cylindrical battery pack format has a natural thermal advantage to prismatic. -- but NOT an ULTIMATE overall advantage.

    /obviously, there's a LOT of factors that go into battery design. I'd kinda have to be a moron not to recognize that,.. wouldn't I?

    // also, -- I really don't like being told directly or have it insinuated that I:
    -- think Tesla is run by morons
    --- I'm sloppy and owe apologies
    -- that I lack critical thinking
    -- that I must be a Tesla short

    etc.. etc...

    it's insulting, inflammatory, and doesn't add anything to the conversation, or to this forum
    Last edited: Feb 26, 2020
    EdwinTheMagnificent likes this.
  18. S Keith

    S Keith Well-Known Member

    I never said nor implied you were a Tesla short.

Share This Page