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The video states a 100kw motor per wheel. Wikipedia states the humvee has a 142kw motor. Not only the vehicle would probably be lighter (batteries vs motor, g

The video states a 100kw motor per wheel. Wikipedia states the humvee has a 142kw motor. Not only the vehicle would probably be lighter (batteries vs motor, gearboxes, etc) but it would have 2.81 more power, so it would probably vastly overperform current vehicles?

goodcanadian 8y ago
Batteries are heavy. It is not immediately clear to me that the overall vehicle would be lighter.
- karambahh 8y ago
  Did not realize how heavy modern batteries still were. Tesla Model 3 batteries weight 480kg for 80.5kWh, density of 167Wh/kg. The DARPA vehicle running for 1h at full power would require a whopping 2400kg of batteries! To give a comparison point, according to Wikipedia, 2400kg is the weight of an Humvee. I guess it'll still take a little while until the DARPA concept becomes an actual vehicle...
  - vegardx 8y ago
    Nothing that stops them from putting in a small turbine to generate electricity. If memory serves me right, this is what some modern tanks do, like the Abraham. Add in a somewhat small (compared to battery powered only) battery pack and you can use that to power the vehicle when idling.
    - SigmundA 8y ago
      Abrahams use mechanical transmission from the turbines. Some ships and trains use diesel electric drivetrains or even turbine electric but its not for weight or efficiency but controllability. My understanding hybrid electric drivetrains are around 80% efficiency, while normal mechanical drivetrains are in the mid 90's. This is why nearly all hybrid cars switch over to normal mechnical drive typically at highway speeds as it more much efficient, while in the city in stop and go the electric drive train beats it due to regeneration and stop light idling.
- samatman 8y ago
  This is true, but I would expect a military vehicle to be a diesel-electric hybrid. As a general rule, diesel-electric is lighter than pure diesel for a given rating, because the generator doesn't need a powertrain.
  - SigmundA 8y ago
    That has not been my experience. Diesel generator-motor sets are much heavier than a diesel engine with mechanical transmission and are less efficient. That does not even take into account a buffer battery weight which you pretty much need for power draw spikes and regenerative braking. Just look at say a Cummins ISB with Allison transmission at 300hp, that's around 225 kilowatts. That combo weighs around 1500 lbs, maybe closer to 2000 with running gear if your comparing to hub motors. A bare frame generator putting out 200+ kw its going to be well over 4000lbs plus whatever hub motors and motor controllers and power systems and batteries weigh. You can go smaller on the generator and make it up on the battery which means more weight, but even a 100kw generator is going to be around 3000lbs and you won't be able to utilize full power for long periods (long grades). Perhaps some advanced generator might be lighter, but it essentially the engine with the same size and weight generator attached to it as needed for motors of equivalent power output. Mechanical transmission on the other hand are pretty light comparatively and have much less losses than the mechanical-electrical-mechanical double conversion.
    - samatman 8y ago
      This isn't a fair comparison, because you're considering a generator that's intended for stationary use. Of course this is going to be heavier than one intended for a vehicle, because the weight isn't a consideration, and lighter is more expensive (more precise, higher-quality materials). What you'd want to be looking at is train powertrains, which are uniformly diesel-electric, because this is the most efficient power configuration. Or the Chevy Volt, for a smaller example which happens to run on gasoline.
      - dsfyu404ed 8y ago
        >this is the most efficient power configuration. Trains have 4+ driven axles mounted on bogies that swivel under the chassis. All wheels must be driven (steel on steel doesn't give you much traction) Diesel electric is used in trains because any mechanic transmission that can do that job would be a Rube Goldberg contraption. A mechanical gearbox is more efficient way of transmitting power because if you've sized things right cruising RPM will be direct drive (no loss from gear friction).
dsfyu404ed 8y ago
The Humvee is a 1970s design and uses an engine that was designed to prioritize fuel economy. Any modern power-train (and many not so modern ones) should vastly outperform a Humvee.

goodcanadian 8y ago

Batteries are heavy. It is not immediately clear to me that the overall vehicle would be lighter.

karambahh 8y ago
Did not realize how heavy modern batteries still were. Tesla Model 3 batteries weight 480kg for 80.5kWh, density of 167Wh/kg. The DARPA vehicle running for 1h at full power would require a whopping 2400kg of batteries! To give a comparison point, according to Wikipedia, 2400kg is the weight of an Humvee. I guess it'll still take a little while until the DARPA concept becomes an actual vehicle...
- vegardx 8y ago
  Nothing that stops them from putting in a small turbine to generate electricity. If memory serves me right, this is what some modern tanks do, like the Abraham. Add in a somewhat small (compared to battery powered only) battery pack and you can use that to power the vehicle when idling.
  - SigmundA 8y ago
    Abrahams use mechanical transmission from the turbines. Some ships and trains use diesel electric drivetrains or even turbine electric but its not for weight or efficiency but controllability. My understanding hybrid electric drivetrains are around 80% efficiency, while normal mechanical drivetrains are in the mid 90's. This is why nearly all hybrid cars switch over to normal mechnical drive typically at highway speeds as it more much efficient, while in the city in stop and go the electric drive train beats it due to regeneration and stop light idling.
samatman 8y ago
This is true, but I would expect a military vehicle to be a diesel-electric hybrid. As a general rule, diesel-electric is lighter than pure diesel for a given rating, because the generator doesn't need a powertrain.
- SigmundA 8y ago
  That has not been my experience. Diesel generator-motor sets are much heavier than a diesel engine with mechanical transmission and are less efficient. That does not even take into account a buffer battery weight which you pretty much need for power draw spikes and regenerative braking. Just look at say a Cummins ISB with Allison transmission at 300hp, that's around 225 kilowatts. That combo weighs around 1500 lbs, maybe closer to 2000 with running gear if your comparing to hub motors. A bare frame generator putting out 200+ kw its going to be well over 4000lbs plus whatever hub motors and motor controllers and power systems and batteries weigh. You can go smaller on the generator and make it up on the battery which means more weight, but even a 100kw generator is going to be around 3000lbs and you won't be able to utilize full power for long periods (long grades). Perhaps some advanced generator might be lighter, but it essentially the engine with the same size and weight generator attached to it as needed for motors of equivalent power output. Mechanical transmission on the other hand are pretty light comparatively and have much less losses than the mechanical-electrical-mechanical double conversion.
  - samatman 8y ago
    This isn't a fair comparison, because you're considering a generator that's intended for stationary use. Of course this is going to be heavier than one intended for a vehicle, because the weight isn't a consideration, and lighter is more expensive (more precise, higher-quality materials). What you'd want to be looking at is train powertrains, which are uniformly diesel-electric, because this is the most efficient power configuration. Or the Chevy Volt, for a smaller example which happens to run on gasoline.
    - dsfyu404ed 8y ago
      >this is the most efficient power configuration. Trains have 4+ driven axles mounted on bogies that swivel under the chassis. All wheels must be driven (steel on steel doesn't give you much traction) Diesel electric is used in trains because any mechanic transmission that can do that job would be a Rube Goldberg contraption. A mechanical gearbox is more efficient way of transmitting power because if you've sized things right cruising RPM will be direct drive (no loss from gear friction).

dsfyu404ed 8y ago

The Humvee is a 1970s design and uses an engine that was designed to prioritize fuel economy. Any modern power-train (and many not so modern ones) should vastly outperform a Humvee.