Re:A Most Peculiar Test Drive
by mpyne on Thursday February 14, 2013 @10:30AM
(#5219855)
Regenerative braking allows you to more efficiently drive within a city.
But the big win is driving at city speeds. I had explained this the other day, but power usage depends approx. on the square of your velocity.
So averaging 30mph in the city would take about 1/4 as much power as averaging 60mph on the highway, all other things being equal.
Normally all other things are not equal, as idling at a city stoplight wastes energy in a gas-powered machine, and pressing the brakes wastes energy in a gas-powered machine.
With an EV idling uses very little energy, and you can reclaim some energy from braking. Braking is still a net loss, but not as much.
Combine the two effects with a 4x power efficiency and it's not at all impossible for a hybrid to get better mileage in city, especially in stop-and-go traffic where the average speed is even lower.
But the big win is driving at city speeds. I had explained this the other day, but power usage depends approx. on the square of your velocity.
So averaging 30mph in the city would take about 1/4 as much power as averaging 60mph on the highway, all other things being equal.
Normally all other things are not equal, as idling at a city stoplight wastes energy in a gas-powered machine, and pressing the brakes wastes energy in a gas-powered machine.
With an EV idling uses very little energy, and you can reclaim some energy from braking. Braking is still a net loss, but not as much.
Combine the two effects with a 4x power efficiency and it's not at all impossible for a hybrid to get better mileage in city, especially in stop-and-go traffic where the average speed is even lower.