TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC

Model S range and interior update imminent?

Discussion in 'Model S' started by Thorbjorn, Jul 29, 2017.

Tags:
  1. wdolson

    wdolson Supporting Member

    Joined:
    Jul 24, 2015
    Messages:
    5,559
    Location:
    Clark Co, WA
    What specifically don't you understand? The tech of supercapacitors? What the 12V battery does? Or something else?
     
  2. Olle

    Olle Member

    Joined:
    Jul 17, 2013
    Messages:
    728
    Location:
    Orlando, FL
    #1862 Olle, Feb 7, 2019
    Last edited: Feb 7, 2019
    I though I understood that the 12V battery powers the car when the HV pack is off or depleted, so that you can unlock the car, communicate with it, open doors after an accident, open windows if the car gets submerged and other nifty things. I don't understand why we have lead acid instead of li-ion for the 12V system. What I really don't understand though is why a capacitor would perform these tasks better than a battery.
     
  3. sandpiper

    sandpiper Active Member

    Joined:
    Sep 25, 2014
    Messages:
    2,607
    Location:
    Ontario, Canada
    As far as I can see, it wouldn't. For a small battery like this, lead acid is cheap and hard to damage. You're not really worried about energy density.

    I do think it's a bit of an anachronism to have this battery in there at all. I'm sure, in the next few years, Tesla will dispense with the silly 12V electrical system altogether and draw accessory power from the main vehicle battery.
     
  4. MP3Mike

    MP3Mike Well-Known Member

    Joined:
    Feb 1, 2016
    Messages:
    7,697
    Location:
    Oregon
    I think the main reason is that you can't charge a li-ion battery when it is below freezing, so you would have to have a battery heater for the 12v battery. It just isn't practical.
     
    • Informative x 1
  5. wdolson

    wdolson Supporting Member

    Joined:
    Jul 24, 2015
    Messages:
    5,559
    Location:
    Clark Co, WA
    The 12V battery is not just an emergency backup, it powers all the electronics in the car. I'm having to replace mine now so I've been searching. There is a company called Ohmmu that makes a LiFePo Li-ion replacement for the lead acid 12V they claim lasts 4X longer. It costs 4X more, but if it means having to get in there 1/4 as often it's worth it. Tesla service charges a fair bit to replace the 12V battery and you have to tear apart the frunk to get at all the bolts holding in the battery (one is buried by the HEPA filter in the S).

    One advantage of supercapacitors is they have vastly more cycles in a lifetime than batteries, and you can rapidly charge and discharge them with no risk of damage. They also don't heat up like batteries do when you rapidly discharge them. Supercapacitors are just capacitors that can hold much more charge than a normal capacitor.

    They are vastly simpler than batteries, they are two electrical plates and a dielectric. The capacity of the capacitor is based on the area of the plates and the qualities of the dielectric. Many cylindrical capacitors are rolled to give them huge surface area to the plate. Think of two sheets of foil wrapped on the same tube. Supercapacitors have come about due to some major advancements in dielectrics that allow for much higher capacity capacitors.

    Capacitors are common in just about all electronic devices. The higher capacity standard capacitors are electrolytics which have a liquid electrolyte. If you see little cans around a circuit board, those are electrolytic capacitors. There were some counterfeit Chinese electrolytics that made their way into computers and TV about 15 years ago and they caused these devices to die prematurely (I restored an NEC monitor I had with replacement capacitors), but if the capacitors are made right, they will last the life of the product.

    Small capacitors are used in many circuit boards to filter out noise picked up from other electronics. The higher the frequency a signal on a wire is, the easier it is for that signal to jump off the wire and get picked up by other wires. Small capacitors placed around the board help filter out these induced signals. Those are so small you wouldn't notice them unless you know what you're looking for. Other times you want to hold a charge for some purpose in electronics. If you've had an electronic device that kept its settings when you changed the batteries, it probably had a capacitor backup to hold power to the circuitry while you changed the batteries. There are other signal conditioning and uses for their use.

    In a car, a supercapacitor replacement for the 12V battery would probably last the life of the car. It could be buried just about anywhere and you could forget about it. Supercapacitors have much lower charge holding capability (per volume) than batteries so for the battery pack that runs the car, they are impractical until they get to at least 10X the current charge density, probably more. Getting supercapacitors with charge densities up around battery cells would be a game changer for the car industry. Supercapacitors are far simpler than li-ion battery chemistry and are both cheaper and far quicker to make. They are also capable of being charged and discharged far faster than batteries which makes supercharging as fast of faster than going to a gas station and it means performance cars would be limited by how much current the motors and wiring can take rather than what the battery can put out.

    While there have been some big improvements in dielectrics that have really boosted the capacity, they are still way below li-ion battery densities. Even if a supercapacitor with the same energy holding ability as the 12V battery in a Tesla took up more space, Tesla could tuck it in just about anywhere they wanted because nobody would ever have to access it.
     
    • Informative x 3
  6. Tiger

    Tiger Active Member

    Joined:
    Oct 31, 2016
    Messages:
    1,032
    Location:
    Estonia
    • Informative x 1
    • Like x 1
  7. sandpiper

    sandpiper Active Member

    Joined:
    Sep 25, 2014
    Messages:
    2,607
    Location:
    Ontario, Canada
    This is interesting. I always wondered what the real numbers were. One thing to note, though, this only talks about the cell level, not the battery level. The 2170 is 5mm taller than the 18650, and so you're going to get 5/65 = 7.6% more energy in the same area vehicle floor, even if the energy density is exactly the same. And we also don't know how much space is lost to cooling/heating/structure/whatnot in the two batteries. Just speculating, with fewer, larger, cells, the 2170 pack probably permits tighter packing.
     
  8. DocZ

    DocZ Member

    Joined:
    Oct 4, 2014
    Messages:
    192
    Location:
    CA
    I'm really struggling to wait for more range in the Model S. May have to go ICE unfortunately, in addition to my X. Hope something happens in the next couple months.
     
    • Like x 1
  9. avesraggiana

    avesraggiana Member

    Joined:
    Jan 25, 2017
    Messages:
    388
    Location:
    Chula Vista CA
    I'm not at that point yet, but man, it would be so great not to have to stop to supercharge at any time during my weekly 280 mile roundtrip commute.

    Note: I could theoretically manage it in an S100D but I'd have to drive at suicidally low freeway speeds. Here in Southern California, nothing less than 80 mph on the 5 between San Diego and LA will do.
     
    • Like x 1
  10. DocZ

    DocZ Member

    Joined:
    Oct 4, 2014
    Messages:
    192
    Location:
    CA
    Absolutely agree. I frequently drive up and down CA, roughly 300 miles one way which means no way I’m hitting that without any stops in the S with real world driving.

    People love to talk about the convenience of super chargers and the need to stop for a break - unfortunately doesn’t work for extremely busy people. When you can complete the same trip without any stops, that matters.
     
    • Like x 2
  11. FlatSix911

    FlatSix911 918 Hybrid

    Joined:
    Jun 15, 2015
    Messages:
    5,423
    Location:
    Silicon Valley
    I believe the volumetric difference has already been accounted for in the analysis based on Wh/kg and Wh/liter... the 18650 wins. :cool:

    upload_2019-2-11_18-41-50.png
     
    • Informative x 1
  12. transpondster

    transpondster Member

    Joined:
    Nov 12, 2014
    Messages:
    150
    Location:
    LT
    well the problem with all those calculations Jack said 2170 weights 70 grams not 70.0, cell capacity measurements are not exact and when you do math on not very exact figure you may get way off numbers
     
  13. Oldschool496

    Oldschool496 Member

    Joined:
    Sep 27, 2017
    Messages:
    272
    Location:
    Florida
    #1873 Oldschool496, Feb 14, 2019 at 8:21 AM
    Last edited: Feb 14, 2019 at 8:28 AM
    I was considering moving to a 100, I can see now through these two posts that its not necessary. Since you have to stop anyway whats the point. Leaving not fully charged though from start and stopping for 10-20 minutes 100 + miles down the road. All depends on geography of where things are located also.

    Of course I am not dealing yet with having to wait for Supercharger and I assume you guys might be waiting or never know you have to wait. That would be frustrating.
     
    • Like x 1

Share This Page

  • About Us

    Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.
  • Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


    SUPPORT TMC