3 ms·

> It's actually friction, for electric cars. Regen is pretty effective at recapturing acceleration, so the energy lost in the wheels is the biggest factor. Mas

by pksadiq 10y ago

> It's actually friction, for electric cars. Regen is pretty effective at recapturing acceleration, so the energy lost in the wheels is the biggest factor. Mass counts much. It's not just about accelerating a still object (car) out of friction. But it's also about working against gravity (g). If the car's acceleration vector is at some angle with gravity (ie, when not perpendicular), more energy will be required to accelerate (when climbing slops), and to break (down the slope). This is very much clear for aircrafts, and other flying objects. Edit: Inertia is also a reason for energy loss in cars (and other moving objects), which increases with mass.

ptaipale 10y ago
The parent mentioned regen and that electric cars are good at it. That means: you don't accelerate infinitely. At some point you decelerate, and then you can regenerate the electric energy. However long you drive uphill, eventually comes the downhill of equal length and you regenerate. I don't know how good exactly electric cars are here, but considering that a Tesla can work as a taxi in the city, it must be pretty good. [edit: punctuation]
hwillis 10y ago
Regeneration recovers a certain percentage of any energy put into speed or altitude. No matter how long you spend climbing you get a good fraction of that energy back. In practice this is pretty quick, and even in stop and go you spend more time at around the same speed than accelerating and slowing. Rolling friction loss is related to speed and is occurring constantly as you drive. That energy is just gone immediately, unlike inertia, which is stored. Say you spend 50% of your time accelerating and braking, and 50% keeping speed. If you regen 80% of the energy and accelerate with 2.5x the power you use to cruise, you're using twice as much energy on friction as accelerating.
jackmott 10y ago
You can get a good % of regen if you slow down slowly, once the brake pads have to touch the rotors, you are throwing energy away. Unless these batteries can accept charge faster, their extra mass won't be offset by more regen.
- spacemanmatt 10y ago
  Except for the risks inherent in large quantities of mechanical inertia stored in a rotating mass, flywheels might seem an attractive option for rapid energy exchange.

by pksadiq 10y ago

ptaipale 10y ago

The parent mentioned regen and that electric cars are good at it. That means: you don't accelerate infinitely. At some point you decelerate, and then you can regenerate the electric energy. However long you drive uphill, eventually comes the downhill of equal length and you regenerate. I don't know how good exactly electric cars are here, but considering that a Tesla can work as a taxi in the city, it must be pretty good. [edit: punctuation]

hwillis 10y ago

Regeneration recovers a certain percentage of any energy put into speed or altitude. No matter how long you spend climbing you get a good fraction of that energy back. In practice this is pretty quick, and even in stop and go you spend more time at around the same speed than accelerating and slowing. Rolling friction loss is related to speed and is occurring constantly as you drive. That energy is just gone immediately, unlike inertia, which is stored. Say you spend 50% of your time accelerating and braking, and 50% keeping speed. If you regen 80% of the energy and accelerate with 2.5x the power you use to cruise, you're using twice as much energy on friction as accelerating.

jackmott 10y ago

You can get a good % of regen if you slow down slowly, once the brake pads have to touch the rotors, you are throwing energy away. Unless these batteries can accept charge faster, their extra mass won't be offset by more regen.

spacemanmatt 10y ago
Except for the risks inherent in large quantities of mechanical inertia stored in a rotating mass, flywheels might seem an attractive option for rapid energy exchange.