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Electric cars and trucks range

05-26-2021, 01:20 PM
Why haven't they come up with a means of charging as long as the vehicle is moving? Some sort of charger that attaches to the rotating assembly to keep the batteries charged as you drive the vehicle down the highway, thus increasing the range indefinitely.

05-26-2021, 04:21 PM
The issue is the drag it would create would negate any gain in battery charge by using that to overcome driving the charger

05-28-2021, 09:54 AM
To Carbuilder's point, you can look at how regenerative braking in electric and hybrid vehicles works. It uses the drag due to charging to slow the vehicle.

It seems to me there was a concept of installing wireless chargers in highway roadbeds years ago for charging electric and hybrid vehicles, but I would imagine the expense to install, maintain, and supply the power were cost-prohibitive, not to mention technical challenges such as making the transfer of energy efficient enough that it offsets the losses due to conversion. Although in the rust belt maybe they could incorporate a heating device in such a system that would also melt snow and ice, saving some on the cost of salt and sand each year.


06-03-2021, 01:29 PM
Do you mean like electrified railway over head power lines?

If a car gets 40 mpg and it's travelling 60 mph, then you're burning gasoline at a rate of (60 mile/hour) / ( 40 miles/gallon ) = 3/2 gallons/hours.

On a good day, then engine converts the combustion heat of the fuel into mechanical energy with about 30% efficency. Electric vehicles get more than 90% of the electrical energy to the wheels (we don't need to worry about the efficiency of charging the battery if we use the energy immediately to power the movement of the vehicle).

Therefor the electricity used to drive the car is 3/2 gallons/hour * 0.3 Egallons/ 0.9 = 1/2 Egallon/hour.

An Egallon is the amount of energy that is available from the combustion of one gallon of gasoline. The value for that is 33.4 kW-hr.

The electrical power needed for the car is:

Energy = 1/2 Egallon/hr * 33.4 kW-hr/Egallon = 16.7 kW.

This the power used by each car driving on the highway.

For reference, a house is often wired for 200 A at 220 volts. The maximum power that the service entry can support is 44 kW, or a bit less than 3x the amount needed to power the car. Occupants rarely use this much power from their electrical service.

A highway designed to power the vehicles will need to account for the maximum number of cars that could be present on the highway, and supply the needed electrical power, so the design needs to account for a worst case situation.

Imagine that your highway has cars running with just one car length between them (15 ft), so on each mile of lane, you'd have 5280 ft/mile / 30 ft/car = 176 cars/mile.

176 cars * 16.7 kW ~ 3 Megawatts of power for each lane-mile of highway. If the highway is two lanes (one in each direction) then the design would need to accommodate 6 Megawatts/mile. That is about the same electrical power that one substation is designed to handle. Double that for four lane highways. Then integrate it for many miles of highway.

Now, consider that my energy load was calculated from the average MPG of the cars, not the peak that would be needed for accelerating or climbing hills.

This is the type of engineering problem that EV solutions present.

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