4 ms·

EVs are already very heavy, and when the model 3 switched to LFP it got even heavier. This mass has lots of subtle consequences that aren't always appreciated.

EVs are already very heavy, and when the model 3 switched to LFP it got even heavier. This mass has lots of subtle consequences that aren't always appreciated. Like accelerated tire wear (which Tesla owners notice after they buy) and increased particulate pollution from that, increased road wear, increased danger to pedestrians and cyclists, etc. So, I'm less excited about LFP. There are a number of ideas in the works that might double the energy density over the current leading lithium ion chemistries and if any of them work out its going to unlock a lot a things that don't quite work yet like: 1. light weight sports car EVs (like a miata) 2. EVs that can tow things or carry 4 mountain bikes on road trips 3. Some aircraft 4. EVs that can do a track day for a reasonable amount of time 5. EVs that are lighter than ICE counterparts rather than heavier

wffurr 4y ago
Wh/Kg is the relevant metric to optimize though. Whether it’s LFP or solid state doesn’t matter. If that company is building higher density LFP batteries, that addresses every concern you mention.
- jackmott 4y ago
  [dead]
Feloevo 4y ago
Independent of this, this also gives more and.better options for the energy grid in general. And economy of scale: if we can produce it, the chance that we can scale it might only be a question of few years.
ericpauley 4y ago
I’ll know we’ve made it when you can buy a 1000kg EV Miata.
seppler 4y ago
Before my Model 3, I had a BMW M3. Curb weights were the same (2009 BMW M3 vs 2018 Model 3 LR RWD). Even comparing a 2020 Model 3 AWD vs. a 2020 BMW M3, curb weights are about the same (~4000lbs).
newZWhoDis 4y ago
> increased danger to pedestrians and cyclists, etc. Why do seemingly so people here understand clipping functions? The lethality of a pedestrian-vehicle collision with a 4,000lb vehicle at 60MPH and a 400,000lb vehicle at 60MPH are both 1 In practical terms, the additional weight of an EV has zero effect on pedestrian collision lethality, whereas something like bumper design would.
- GaryNumanVevo 4y ago
  Higher curb weight correlates with longer breaking distances
- AlotOfReading 4y ago
  I'm not sure why clipping functions are relevant, because the probability of death isn't 100% even for semis hitting pedestrians at highway speeds. It's actually more like 80-90%. There's still quite a bit of long tail for higher speeds beyond that as well. SUVs and other "heavy" consumer vehicles are somewhere in the 75% range at comparable speeds, while sedans are down around 65% mortality. Feel free to find your own numbers, but I'm using [1]. Vehicle weight and size clearly have a significant effect on mortality even at high speeds. However, not all collisions are at highway speed. Most collisions are at relatively low speed, where weight is an even more significant factor in the energy involved. There are tradeoffs you can make between weight contributed by safety equipment (e.g. bumpers), but to a large extent those tradeoffs are mandated by regulations rather than consumers or OEM engineers. [1] https://www.moneygeek.com/insurance/auto/analysis/pedestrian-chance-of-survival/ https://www.moneygeek.com/insurance/auto/analysis/pedestrian... [2] https://www.nber.org/digest/nov11/vehicle-weight-and-automotive-fatalities https://www.nber.org/digest/nov11/vehicle-weight-and-automot...
  - meatmanek 4y ago
    Vehicle mass matters a lot in vehicle-to-vehicle collisions, where the energy and momentum of each vehicle is going to change a lot, but when a car collides with a person, the car's momentum is barely affected, because the car is already significantly more massive than the person. A 20x mass ratio is already practically infinite. In a direct collision between a moving 1000kg car going 10 m/s and a stationary 50kg person, the person will end up moving somewhere between 9.5 m/s (perfectly inelastic collision) and 19.05 m/s (perfectly elastic). The car will end up moving 9.5 m/s (perfectly inelastic) and 9.05 m/s (perfectly elastic). In a direct collision between a moving 10000kg car going 10 m/s and a stationary 50kg person, the person will end up moving 9.95 m/s (perfectly inelastic) and 19.90 m/s (perfectly elastic). The car will end up moving somewhere between 9.95 m/s (perfectly inelastic) and 9.90 m/s (perfectly elastic). Even though we 10x'd the weight of the car, we only increased the velocity of the person after impact by about 5%, and energy imparted on the person by about 10%. I suspect vehicle size (or rather, the size/shape of the front of the vehicle) has way more effect on pedestrian survivability than the weight of the vehicle. SUVs and trucks will impart the force of impact directly to your torso and head, and then subsequently run you over. Sedans hit you in the legs and then roll you over the top of the vehicle.

wffurr 4y ago

Wh/Kg is the relevant metric to optimize though. Whether it’s LFP or solid state doesn’t matter. If that company is building higher density LFP batteries, that addresses every concern you mention.

jackmott 4y ago
[dead]

Feloevo 4y ago

Independent of this, this also gives more and.better options for the energy grid in general. And economy of scale: if we can produce it, the chance that we can scale it might only be a question of few years.

ericpauley 4y ago

I’ll know we’ve made it when you can buy a 1000kg EV Miata.

seppler 4y ago

Before my Model 3, I had a BMW M3. Curb weights were the same (2009 BMW M3 vs 2018 Model 3 LR RWD). Even comparing a 2020 Model 3 AWD vs. a 2020 BMW M3, curb weights are about the same (~4000lbs).

newZWhoDis 4y ago

> increased danger to pedestrians and cyclists, etc. Why do seemingly so people here understand clipping functions? The lethality of a pedestrian-vehicle collision with a 4,000lb vehicle at 60MPH and a 400,000lb vehicle at 60MPH are both 1 In practical terms, the additional weight of an EV has zero effect on pedestrian collision lethality, whereas something like bumper design would.

GaryNumanVevo 4y ago
Higher curb weight correlates with longer breaking distances
AlotOfReading 4y ago
I'm not sure why clipping functions are relevant, because the probability of death isn't 100% even for semis hitting pedestrians at highway speeds. It's actually more like 80-90%. There's still quite a bit of long tail for higher speeds beyond that as well. SUVs and other "heavy" consumer vehicles are somewhere in the 75% range at comparable speeds, while sedans are down around 65% mortality. Feel free to find your own numbers, but I'm using [1]. Vehicle weight and size clearly have a significant effect on mortality even at high speeds. However, not all collisions are at highway speed. Most collisions are at relatively low speed, where weight is an even more significant factor in the energy involved. There are tradeoffs you can make between weight contributed by safety equipment (e.g. bumpers), but to a large extent those tradeoffs are mandated by regulations rather than consumers or OEM engineers. [1] https://www.moneygeek.com/insurance/auto/analysis/pedestrian-chance-of-survival/ https://www.moneygeek.com/insurance/auto/analysis/pedestrian... [2] https://www.nber.org/digest/nov11/vehicle-weight-and-automotive-fatalities https://www.nber.org/digest/nov11/vehicle-weight-and-automot...
- meatmanek 4y ago
  Vehicle mass matters a lot in vehicle-to-vehicle collisions, where the energy and momentum of each vehicle is going to change a lot, but when a car collides with a person, the car's momentum is barely affected, because the car is already significantly more massive than the person. A 20x mass ratio is already practically infinite. In a direct collision between a moving 1000kg car going 10 m/s and a stationary 50kg person, the person will end up moving somewhere between 9.5 m/s (perfectly inelastic collision) and 19.05 m/s (perfectly elastic). The car will end up moving 9.5 m/s (perfectly inelastic) and 9.05 m/s (perfectly elastic). In a direct collision between a moving 10000kg car going 10 m/s and a stationary 50kg person, the person will end up moving 9.95 m/s (perfectly inelastic) and 19.90 m/s (perfectly elastic). The car will end up moving somewhere between 9.95 m/s (perfectly inelastic) and 9.90 m/s (perfectly elastic). Even though we 10x'd the weight of the car, we only increased the velocity of the person after impact by about 5%, and energy imparted on the person by about 10%. I suspect vehicle size (or rather, the size/shape of the front of the vehicle) has way more effect on pedestrian survivability than the weight of the vehicle. SUVs and trucks will impart the force of impact directly to your torso and head, and then subsequently run you over. Sedans hit you in the legs and then roll you over the top of the vehicle.