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An electric motor is more efficient mostly because of regenerative braking. Not having an engine with variable RPM helps. They should make a car that's basical

by ars 4y ago

An electric motor is more efficient mostly because of regenerative braking. Not having an engine with variable RPM helps. They should make a car that's basically a generator charging a medium sized battery, and everything else is electric. (Don't directly power the wheels from the engine, that makes things too complicated.) Kind of like a diesel-electric train, but with a battery to capture energy from regenerative braking, and for surge power.

mbrock 4y ago
Isn’t that just a series hybrid?
- ars 4y ago
  Yes, that's exactly what that is, and apparently there are none for sale. There must be a reason why not, but I don't know what it is.
  - Gordonjcp 4y ago
    It's not very efficient, certainly not enough to be "better" than a conventional IC-engined car. You're carrying around a lot of batteries, motor, and generator that are basically just dead weight. A petrol engine and gearbox is light. In trains it works quite well because you need an immense amount of torque to pull away, proportionately far far more than you need from even a large truck, and then you need a relatively small amount of power to keep it moving. Having a big generator driving bogey-mounted traction motors with simple reduction boxes means you don't need a huge gearbox and very complicated driveshaft system, and you don't care so much about weight.
    - majewsky 4y ago
      I've seen this series-hybrid system also used in buses in my town. I'm not a mechanical or electrical engineer, but as far as I understand, the advantage in this scenario is that the motor can run nearly continuously at lower RPM where it is apparently more efficient. The spike in power usage that's needed during acceleration is then handled by the battery acting as a buffer.
  - krallja 4y ago
    Chevy had one called the Volt, but ended production in 2019. From Wikipedia: “In 2018, General Motors decided to end production in March 2019. The primary reason given was that the Volt is a sedan, and sales of traditional sedans were in decline. Car salesmen were proving resistant to selling the car because it was more complicated (and thus took more of their time) to explain how the vehicle operated. Marketing trends showed that sales of hybrids were dropping as more customers were turning to all-electric vehicles like the Chevrolet Bolt. The range-anxiety associated with all-electric vehicles had been in decline due to better battery technology, and most hybrid drivers were turning on their gas-powered engines less frequently. The battery technology developed for the Volt had already been incorporated into the Bolt.”
danhor 4y ago
No, the regenerative breaking isn't the reason why electric vehicles are more efficient. Traditional ICE are very inefficient, only converting 20% of chemical energy to kinetic energy (with the rest being turned to heat). Diesels are a better at 40%. (modern ccs gas power plants get to 65% from gas to electricity) Electric motors in cars are approx. 90% efficient. Combined with charging losses and others, that comes out to approx. 70%-80%. Regenarative breaking only adds an additional ~20%.

by ars 4y ago

mbrock 4y ago

Isn’t that just a series hybrid?

ars 4y ago
Yes, that's exactly what that is, and apparently there are none for sale. There must be a reason why not, but I don't know what it is.
- Gordonjcp 4y ago
  It's not very efficient, certainly not enough to be "better" than a conventional IC-engined car. You're carrying around a lot of batteries, motor, and generator that are basically just dead weight. A petrol engine and gearbox is light. In trains it works quite well because you need an immense amount of torque to pull away, proportionately far far more than you need from even a large truck, and then you need a relatively small amount of power to keep it moving. Having a big generator driving bogey-mounted traction motors with simple reduction boxes means you don't need a huge gearbox and very complicated driveshaft system, and you don't care so much about weight.
  - majewsky 4y ago
    I've seen this series-hybrid system also used in buses in my town. I'm not a mechanical or electrical engineer, but as far as I understand, the advantage in this scenario is that the motor can run nearly continuously at lower RPM where it is apparently more efficient. The spike in power usage that's needed during acceleration is then handled by the battery acting as a buffer.
- krallja 4y ago
  Chevy had one called the Volt, but ended production in 2019. From Wikipedia: “In 2018, General Motors decided to end production in March 2019. The primary reason given was that the Volt is a sedan, and sales of traditional sedans were in decline. Car salesmen were proving resistant to selling the car because it was more complicated (and thus took more of their time) to explain how the vehicle operated. Marketing trends showed that sales of hybrids were dropping as more customers were turning to all-electric vehicles like the Chevrolet Bolt. The range-anxiety associated with all-electric vehicles had been in decline due to better battery technology, and most hybrid drivers were turning on their gas-powered engines less frequently. The battery technology developed for the Volt had already been incorporated into the Bolt.”

danhor 4y ago

No, the regenerative breaking isn't the reason why electric vehicles are more efficient. Traditional ICE are very inefficient, only converting 20% of chemical energy to kinetic energy (with the rest being turned to heat). Diesels are a better at 40%. (modern ccs gas power plants get to 65% from gas to electricity) Electric motors in cars are approx. 90% efficient. Combined with charging losses and others, that comes out to approx. 70%-80%. Regenarative breaking only adds an additional ~20%.