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Electric semis for true long haul will never be viable unless there is a major breakthrough in battery tech. 300 gallons of diesel fuel has so much more energy

Electric semis for true long haul will never be viable unless there is a major breakthrough in battery tech. 300 gallons of diesel fuel has so much more energy than even the best batteries could pack into a reasonable size and weight.

KillerRabbitt 9y ago
Major breakthroughs in autonomous driving may change that. If drivers are eliminated, the costs of waiting 30-60 minutes while charging becomes almost 0.
- hughes 9y ago
  Especially if the truck can hand off its payload to a fully charged & waiting replacement cab. If you have access to a fleet or don't need the same truck back, it becomes more of a baton relay than a marathon.
- TillE 9y ago
  With the kind of infrastructure required for that, I can't help but think it would just be a lousy version of an electric railway. At least for long hauls with high throughput.
  - colordrops 9y ago
    That's like saying that circuit switched networks are better than packet switched.
    - amluto 9y ago
      They would be if packets had enormous per-packet overhead.
  - Gibbon1 9y ago
    At some point you start wondering about improving intermodal transportation. Using rail for longer distances with trucks handling the last 50-100 miles.
  - tomhschmidt 9y ago
    How would it be lousy? The cars can now go anywhere and dynamically route instead of being stuck on rails and the infrastructure costs are orders of magnitude less.
- hobofan 9y ago
  Isn't it the other way around? With drivers, you can fit the charging inside the already mandated breaks, while without driver, you have to introduce longer breaks to get enough charge. Idle time of EV-rig per day (30min charge every 4 hours): ~11% Idle time of Non-EV-rig per day (5min refueling every 4 hours): ~2% Sure, for short distance trips where loading/unloading takes as long as charging the EV-rig, it doesn't make a difference, but for longer hauls, the charging pauses of EV-rigs will severely cut into utilization of the fleet.
MichaelApproved 9y ago
Would a hybrid system using an electric generator to recharge the batteries be more efficient given the advantages of electric vehicles, such as regenerative braking?
- ams6110 9y ago
  I would think if a series hybrid were more efficient than a conventional mechanical drive and transmission, it would already have been adopted. Trucking companies will spend money even for small gains in fuel efficiency because they drive so many miles. I also think that regen braking in semis would be trickier because a lot of the braking happens on the trailer wheels so you would need to fit all the trailers with regenerative braking equipment.
- Retric 9y ago
  Long haul trucks fairly hit the breaks as that ends up costing a lot of money. However, a truck specifically for mountainous areas may benifit from a hybrid transmission.
Retric 9y ago
Semi's actually get ~6.5 MPG so they only need around 5x the batteries to get the same distance as normal electric cars. The huge tanks are over 24 hours driving time and are most there so you can pick the states to refuel in. Battery volume and weight density is not that bad when you consider the weight savings without an IC engine, transmission etc. Gasoline gallon equivalent tables ignore the vastly lower efficiency of IC engines. Costs are mostly non issue as trucks would charge daily making them break even before cars. The actual problem is manufacturing capacity which has been ramping up but has a long way to go.
- ams6110 9y ago
  Yes but long haul trucking involves distances much farther then the range of any normal electric car. Good point about substituting the weight of the engine for batteries. Still I think you're going to be way short in total energy density. And it's not like you can just pack the trailer with batteries either, you still need to allow for the weight of the cargo and there is a gross weight limit on 18-wheelers.
  - Jesus_Jones 9y ago
    they are already driving them, they seem to have about the range. you can read about this in tesla newsgroup sites, like tmc.
  - Retric 9y ago
    They don't exceed highway speed so swapping batteries every X miles will be worth it if they reduce total costs by doing so. As to weight the engine weighs ~3000 lb and 300 gallons of gas weigh ~1,900 gallons. Transmission is another 700lb, include tank weight and verious odds and ends and you can get ~5 hours at highway speed. Assuming a battery swap takes 10 minutes. That's easily worth saving 50+k per year in operating expenses.
    - femidav 9y ago
      2200lb for gas, 3000lb for the engine, 700lb for the transmission. Say 7k lb total. Compare this now to the electric one. The battery alone would weight 33k pounds. Engine and transmission would add another 2k. 5 times more than ICE. The battery would also cost $200k.
paranoidrobot 9y ago
Most trucks are driven by a single driver, rather than a team of drivers - this means that they legally must have 30-60 minute breaks every few hours, and can only drive a certain number of hours. So, lets throw some numbers around: - Range: 500 miles - Time to recharge 80% (+400 miles) capacity - 30 minutes - Speed Limit (Interstates): 50-75MPH - Maximum Driving Times (USDOT): - 8 hours (followed by a 30min break), - 14 hours (followed by a 10 hour break) - 60/70 hours (in any 7/8 days) So lets assume 60MPH moving average speed (very high) - gives us over 8.3 hours of driving time. You add in a 30min break at a megacharger and you've now got yourself another 400 miles of range, which would let you drive for 6.6 hours - at which point you'll be out of hours again. So you park up and let the truck charge overnight. I don't see how this is so difficult.
- hueving 9y ago
  Where are you getting 400 mile range on a semi towing a load coming from 30 minutes of charging?
  - BinaryIdiot 9y ago
    Tesla was mentioning 400 miles. I _could have sworn_ they specified those numbers were all with an average load but it seems official numbers are a bit annoying to source. So now I'm curious if that's accurate or not.
  - _ph_ 9y ago
    That is the number Tesla promised for their megachargars at the presentation of the semi. So they seem to have clear plans to deploy megawatt chargers at their charging stations.
  - paranoidrobot 9y ago
    For the range - you can order either 300 or 500 mile range options. The range options were said by Tesla to be the range of the truck plus trailer and maximum load, at highway speeds. The 400 mile mention is the 80% capacity of a 500 mile range pack you'd get by a 30 minute charge. Also information given during the announcement. [1] https://www.tesla.com/semi https://www.tesla.com/semi
colordrops 9y ago
Are you suggesting that Tesla hasn't done the math or are just flat out lying?
- greglindahl 9y ago
  He used the weasel words "true long haul". Tesla was clear about what the truck can do; you're replying to someone who wants to argue with unclear statements. Not a good plan.

KillerRabbitt 9y ago

Major breakthroughs in autonomous driving may change that. If drivers are eliminated, the costs of waiting 30-60 minutes while charging becomes almost 0.

hughes 9y ago
Especially if the truck can hand off its payload to a fully charged & waiting replacement cab. If you have access to a fleet or don't need the same truck back, it becomes more of a baton relay than a marathon.
TillE 9y ago
With the kind of infrastructure required for that, I can't help but think it would just be a lousy version of an electric railway. At least for long hauls with high throughput.
- colordrops 9y ago
  That's like saying that circuit switched networks are better than packet switched.
  - amluto 9y ago
    They would be if packets had enormous per-packet overhead.
- Gibbon1 9y ago
  At some point you start wondering about improving intermodal transportation. Using rail for longer distances with trucks handling the last 50-100 miles.
- tomhschmidt 9y ago
  How would it be lousy? The cars can now go anywhere and dynamically route instead of being stuck on rails and the infrastructure costs are orders of magnitude less.
hobofan 9y ago
Isn't it the other way around? With drivers, you can fit the charging inside the already mandated breaks, while without driver, you have to introduce longer breaks to get enough charge. Idle time of EV-rig per day (30min charge every 4 hours): ~11% Idle time of Non-EV-rig per day (5min refueling every 4 hours): ~2% Sure, for short distance trips where loading/unloading takes as long as charging the EV-rig, it doesn't make a difference, but for longer hauls, the charging pauses of EV-rigs will severely cut into utilization of the fleet.

MichaelApproved 9y ago

Would a hybrid system using an electric generator to recharge the batteries be more efficient given the advantages of electric vehicles, such as regenerative braking?

ams6110 9y ago
I would think if a series hybrid were more efficient than a conventional mechanical drive and transmission, it would already have been adopted. Trucking companies will spend money even for small gains in fuel efficiency because they drive so many miles. I also think that regen braking in semis would be trickier because a lot of the braking happens on the trailer wheels so you would need to fit all the trailers with regenerative braking equipment.
Retric 9y ago
Long haul trucks fairly hit the breaks as that ends up costing a lot of money. However, a truck specifically for mountainous areas may benifit from a hybrid transmission.

Retric 9y ago

Semi's actually get ~6.5 MPG so they only need around 5x the batteries to get the same distance as normal electric cars. The huge tanks are over 24 hours driving time and are most there so you can pick the states to refuel in. Battery volume and weight density is not that bad when you consider the weight savings without an IC engine, transmission etc. Gasoline gallon equivalent tables ignore the vastly lower efficiency of IC engines. Costs are mostly non issue as trucks would charge daily making them break even before cars. The actual problem is manufacturing capacity which has been ramping up but has a long way to go.

ams6110 9y ago
Yes but long haul trucking involves distances much farther then the range of any normal electric car. Good point about substituting the weight of the engine for batteries. Still I think you're going to be way short in total energy density. And it's not like you can just pack the trailer with batteries either, you still need to allow for the weight of the cargo and there is a gross weight limit on 18-wheelers.
- Jesus_Jones 9y ago
  they are already driving them, they seem to have about the range. you can read about this in tesla newsgroup sites, like tmc.
- Retric 9y ago
  They don't exceed highway speed so swapping batteries every X miles will be worth it if they reduce total costs by doing so. As to weight the engine weighs ~3000 lb and 300 gallons of gas weigh ~1,900 gallons. Transmission is another 700lb, include tank weight and verious odds and ends and you can get ~5 hours at highway speed. Assuming a battery swap takes 10 minutes. That's easily worth saving 50+k per year in operating expenses.
  - femidav 9y ago
    2200lb for gas, 3000lb for the engine, 700lb for the transmission. Say 7k lb total. Compare this now to the electric one. The battery alone would weight 33k pounds. Engine and transmission would add another 2k. 5 times more than ICE. The battery would also cost $200k.

paranoidrobot 9y ago

Most trucks are driven by a single driver, rather than a team of drivers - this means that they legally must have 30-60 minute breaks every few hours, and can only drive a certain number of hours. So, lets throw some numbers around: - Range: 500 miles - Time to recharge 80% (+400 miles) capacity - 30 minutes - Speed Limit (Interstates): 50-75MPH - Maximum Driving Times (USDOT): - 8 hours (followed by a 30min break), - 14 hours (followed by a 10 hour break) - 60/70 hours (in any 7/8 days) So lets assume 60MPH moving average speed (very high) - gives us over 8.3 hours of driving time. You add in a 30min break at a megacharger and you've now got yourself another 400 miles of range, which would let you drive for 6.6 hours - at which point you'll be out of hours again. So you park up and let the truck charge overnight. I don't see how this is so difficult.

hueving 9y ago
Where are you getting 400 mile range on a semi towing a load coming from 30 minutes of charging?
- BinaryIdiot 9y ago
  Tesla was mentioning 400 miles. I _could have sworn_ they specified those numbers were all with an average load but it seems official numbers are a bit annoying to source. So now I'm curious if that's accurate or not.
- _ph_ 9y ago
  That is the number Tesla promised for their megachargars at the presentation of the semi. So they seem to have clear plans to deploy megawatt chargers at their charging stations.
- paranoidrobot 9y ago
  For the range - you can order either 300 or 500 mile range options. The range options were said by Tesla to be the range of the truck plus trailer and maximum load, at highway speeds. The 400 mile mention is the 80% capacity of a 500 mile range pack you'd get by a 30 minute charge. Also information given during the announcement. [1] https://www.tesla.com/semi https://www.tesla.com/semi

colordrops 9y ago

Are you suggesting that Tesla hasn't done the math or are just flat out lying?

greglindahl 9y ago
He used the weasel words "true long haul". Tesla was clear about what the truck can do; you're replying to someone who wants to argue with unclear statements. Not a good plan.