7 ms·

11,000pounds for a battery implies 170Wh/kg. High end lithium ion cells can do about 300Wh/kg, and even with some overhead for the battery, we’re talking 250Wh/

11,000pounds for a battery implies 170Wh/kg. High end lithium ion cells can do about 300Wh/kg, and even with some overhead for the battery, we’re talking 250Wh/kg.. So… That’s beatable, & we can’t back out the weight directly from the energy of the pack as we know Tesla has been working on improving chemistry and specific energy and pack efficiency. Anyway, the claim by Musk that they can achieve 1.5kWh/mile is reasonable, and fits in with my calculations here: https://selenianboondocks.com/2017/11/tesla-semi-part-1/ https://selenianboondocks.com/2017/11/tesla-semi-part-1/ The vehicles that they delivered did not use all the available aerodynamics tricks that their prototypes did, and uses duals instead of super singles, so it also makes sense it’s only achieving 1.7kWh/mile right now. Note that a ton of people claimed a 500 mile electric semi with a full load wasn’t feasible. This proves that it is. (The jersey barriers they pulled weighed about a standard 44,000pounds.) The Toyota hydrogen semi has only about a 300 mile range and with fuel an order of magnitude more expensive.

reportingsjr 4y ago
You're talking about battery cells, but you need to look at the battery _pack_ energy density. The model 3 battery pack, which uses the same cells as semi, is about 170Wh/kg. The numbers in TFA are very reasonable estimates.
- Robotbeat 4y ago
  I already addressed that by including mass overhead for the overall battery. And sure, it’s always possible to assume more conservative numbers for a whole battery and assume Tesla DIDN’T do any engineering work to reduce overall battery mass, but that’s not something you should put in a headline. (Tesla has typically done better than their peers in overall battery specific energy as well as energy per mile.)
  - 0_____0 4y ago
    You're using a 16-17% figure for packaging overhead? That's low. Even with relatively expensive construction techniques (for example if you're doing EVTOL) you see 20-25% packaging overhead.
    - Robotbeat 4y ago
      I agree, but a long haul, full payload electric Semi is a very challenging project comparable to an electric aircraft since you’re limited to near the same maximum total weight. I’m merely pointing out that such a battery pack is one possible solution, one that cannot be ruled out based on public information.
      - 0_____0 4y ago
        The in-use 2170 batteries are apparently 250Wh/kg. With that figure and a more realistic packaging overhead of 30% I'm seeing something like 190Wh/kg, which is more in line with your observation. From the numbers I can find, the Model S 85kWh has 7104 18650 cells - if we use 49g for mass of cell, that's 767lb of cell vs the pack weight of 1200lb~, or a very rough packaging overhead of ~36% This is a naïve analysis but it helps assuage my ego, as I've worked on designs for 26650 based packs where we would have been quite happy to hit 30% overhead :) That being said, I realize people can, and do in fact make more mass efficient packs.
trollerator23 4y ago
Wow, selenianboondocks. That's a blast from the past.
unwind 4y ago
Okay, cool. So if I read [1] right, some kind of average price for electricity used in the transport sector in the US as of September 2022 was 12.48 cents/kWh. That would mean that the 500-mile trip costs 500 * 1.5 * 12.48 / 100 = $93.6 in energy. If that includes hauling tens of thousands of pounds of cargo, that sounds rather a lot like it would make transport powered by electricity commercially sane, right? Nice. EDIT: I hadn't read the article much; it seems the current power value given is actually 1.7 kWh/mile, so that increased the price to 500 * 1.7 * 12.48 / 100 = $106.08. Not a huge increase, obviously.
- verdenti 4y ago
  Thanks for that math. Seems relatively cheap. How does it compare to gasoline?
  - lern_too_spel 4y ago
    You appear to be shadow-banned because of your second ever comment, which, while wildly offensive, does not appear to be a statement that you believe but instead an explanation of what Meloni believes.
  - mbell 4y ago
    (500mi / 6.5mpg) * $5.313 = $408.69 6.5mpg - I just Googled average MPG for a fully loaded Semi, could be wrong. $5.313 - Most recent highway diesel price (https://www.eia.gov/petroleum/gasdiesel/ https://www.eia.gov/petroleum/gasdiesel/). I'd expect this is high due to fleet discounts and such.
    - olyjohn 4y ago
      I feel like that average is really low. Talking with my buddy who is a trucker, he said that 6mpg is on the low end. His truck, which isn't anything special, would usually get 8-9. He said those guys getting 6 or lower are usually owner / operators who have older trucks, either because they like the older trucks or they can't afford to get a new one. Most fleets have much newer trucks, a lot of which can get up to 10mpg or more. That may not seem like a huge improvement, but over thousands of miles it adds up really fast.

reportingsjr 4y ago

You're talking about battery cells, but you need to look at the battery _pack_ energy density. The model 3 battery pack, which uses the same cells as semi, is about 170Wh/kg. The numbers in TFA are very reasonable estimates.

Robotbeat 4y ago
I already addressed that by including mass overhead for the overall battery. And sure, it’s always possible to assume more conservative numbers for a whole battery and assume Tesla DIDN’T do any engineering work to reduce overall battery mass, but that’s not something you should put in a headline. (Tesla has typically done better than their peers in overall battery specific energy as well as energy per mile.)
- 0_____0 4y ago
  You're using a 16-17% figure for packaging overhead? That's low. Even with relatively expensive construction techniques (for example if you're doing EVTOL) you see 20-25% packaging overhead.
  - Robotbeat 4y ago
    I agree, but a long haul, full payload electric Semi is a very challenging project comparable to an electric aircraft since you’re limited to near the same maximum total weight. I’m merely pointing out that such a battery pack is one possible solution, one that cannot be ruled out based on public information.
    - 0_____0 4y ago
      The in-use 2170 batteries are apparently 250Wh/kg. With that figure and a more realistic packaging overhead of 30% I'm seeing something like 190Wh/kg, which is more in line with your observation. From the numbers I can find, the Model S 85kWh has 7104 18650 cells - if we use 49g for mass of cell, that's 767lb of cell vs the pack weight of 1200lb~, or a very rough packaging overhead of ~36% This is a naïve analysis but it helps assuage my ego, as I've worked on designs for 26650 based packs where we would have been quite happy to hit 30% overhead :) That being said, I realize people can, and do in fact make more mass efficient packs.

trollerator23 4y ago

Wow, selenianboondocks. That's a blast from the past.

unwind 4y ago

Okay, cool. So if I read [1] right, some kind of average price for electricity used in the transport sector in the US as of September 2022 was 12.48 cents/kWh. That would mean that the 500-mile trip costs 500 * 1.5 * 12.48 / 100 = $93.6 in energy. If that includes hauling tens of thousands of pounds of cargo, that sounds rather a lot like it would make transport powered by electricity commercially sane, right? Nice. EDIT: I hadn't read the article much; it seems the current power value given is actually 1.7 kWh/mile, so that increased the price to 500 * 1.7 * 12.48 / 100 = $106.08. Not a huge increase, obviously.

verdenti 4y ago
Thanks for that math. Seems relatively cheap. How does it compare to gasoline?
- lern_too_spel 4y ago
  You appear to be shadow-banned because of your second ever comment, which, while wildly offensive, does not appear to be a statement that you believe but instead an explanation of what Meloni believes.
- mbell 4y ago
  (500mi / 6.5mpg) * $5.313 = $408.69 6.5mpg - I just Googled average MPG for a fully loaded Semi, could be wrong. $5.313 - Most recent highway diesel price (https://www.eia.gov/petroleum/gasdiesel/ https://www.eia.gov/petroleum/gasdiesel/). I'd expect this is high due to fleet discounts and such.
  - olyjohn 4y ago
    I feel like that average is really low. Talking with my buddy who is a trucker, he said that 6mpg is on the low end. His truck, which isn't anything special, would usually get 8-9. He said those guys getting 6 or lower are usually owner / operators who have older trucks, either because they like the older trucks or they can't afford to get a new one. Most fleets have much newer trucks, a lot of which can get up to 10mpg or more. That may not seem like a huge improvement, but over thousands of miles it adds up really fast.