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Old 07-13-2014, 10:42 PM   #22 (permalink)
NeilBlanchard
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Do you watch your gas gauge? You won't "suddenly" lose the battery, in an EV, either.

Here's how Tesla can build the Model E (or whatever it gets called):

The same way that the Illuminati Motor Works '7' goes 220+ miles on a 33kWh pack at 60-70mph on flat-ish ground in low wind, and it uses just ~129Wh/mile:

Low aero drag, free wheel coasting (with regen only when the driver needs it) and improved wall-to-wheel efficiency. The '7' has an AC synchronous motor, so no permanent magnets dragging when you coast. It loses just ~8% vs the ~15% for typical EV's, because it uses no BMS. They bottom balanced the pack (99 CALB 100Ah cells) instead. Much less heat during charging - less heat means less energy lost.

I cannot stress enough about free wheel coasting - the kinetic energy you "invested" in when the car accelerates is used most effectively to - wait for it - move the car forward. Aero drag is the only loss, and you get that all the time anyway.

Use regen only when you need to slow the car. The result is significantly less acceleration, and much less regen is needed to used - so the losses of regen are avoided.

Weight is less of a penalty for EV's for several reasons: electric motors are far more efficient, and so the losses to accelerate the mass is much lower than in an ICE. ICEs are terrible efficiency during acceleration, and even at their peak, when cruising at a steady speed, they are still losing ~3X more energy than an EV does.

Secondly, when coasting, an EV has no consumption. As I mentioned, an AC synchronous motor is better at this than a motor with permanent magnets.

With regen (as needed) that is two ways that the energy "invested" in accelerating the mass of the car (kinetic energy) is regained.

Aero drag is always a *total* loss.

At 30MPH typical cars are losing HALF the energy to aero drag. At 55MPH, they lose 75%, and at higher speeds it quickly goes up to 85-90%.

If the drivetrain is already losing ~75% then those two things are *by far* the most important factors to moving the car forward on as little energy as possible. If the EV drive train is losing 15% then that is a lot better, but if it is only losing ~8%, then that is better still.

Low aero drag is a virtuous circle: low consumption goes much farther on a smaller battery, which both weighs less and costs less, and takes up less room in the chassis.

Other ways to lower consumption are to have "thin" but ergonomic seats. They are perfectly comfortable (if designed right) and they weigh less and take up less room, so you either get a roomier interior and/or the car can be smaller. So, it weighs less and costs less.

Thermal insulation in the chassis, means that (like in a building) the temperature inside the car is more stable without adding energy to either heat or cool it.

All EVs should have direct heating electric defrosters. These take a fraction of the energy and they work very quickly. Like heated seats, by heating the important bits directly, you save a *lot* of energy in the winter.

Heat pumps are becoming common in EVs. Other things to do are use well located air intakes and exhaust vents to passively move air through the vehicle.

I have every confidence that Tesla (and maybe Nissan, and Kia, and VW, and Mitsubishi, and BMW, and Mercedes - and possibly even GM!) can build a ground up EV that takes full advantage of good engineering - that they can sell us a 200+ mile EV for the $30-40K that seems to be the sweet spot. And we should be able to get 125-160 mile EV's for less, as well.
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http://neilblanchard.blogspot.com/
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