Toyota shows off its new iQ electric-car prototype

Any specs on such things as how many Kw/hr per mile or just how much energy is stored in the battery? Or how much energy does it take to recharge, does it require 220 or can it get by on 110? 110 at 20 amps, typical max of home plugs would only be about 3 hp, 2000 watts so in 8 hours would be able to shove only about 16 kw/hr into the battery. They claim 100 Km or 60 odd miles and if we assume that is at 100 km/hr that would be one hour of driving, so if that is correct, 16 Kw/hr for 100 km would be extremely efficient electrically speaking. That would be about 20 hp for an hour. That would be excellent if true.

Don't worry Sonhouse, the car makers just like to demonstrate these vehicles at the auto shows because they want to have something there that pique peoples interests.

I doubt that they have any real actual desire to manufacture these. They would lose too much income from parts sales, oil changes, and other revenue streams typical to the otto engines.

Why not make the chassis the battery? That would save alot of weight. Also why is there no direct wheel motors on the wheels ?

A fair assumption for everyday road cars would be .3 kWh per mile based on driving reports from the other electric cars.

Why not make the chassis the battery? That would save alot of weight. Also why is there no direct wheel motors on the wheels ?

Because wheel motors are difficult to optimize for high/low speeds and difficult for the suspension system. They're basically too inefficient as a compromize.

Because wheel motors are difficult to optimize for high/low speeds and difficult for the suspension system. They're basically too inefficient as a compromize.

nonsense... with direct wheel motors you can reduce alot of weight, and with sensors you can easily regulate the speed of the wheels. Also taking corners would be more efficient cause the car can make one side spin faster than the other.

nonsense... with direct wheel motors you can reduce alot of weight

Despite that, a lot more weight will be unsprung, which hurts handling and ride quality a lot. When a heavier wheel bounces from a pothole, the motion carries a lot more energy that has to be damped by the suspension. It jostles the car around much harder. And the heavy batteries will void the weight advantage anyways.

And every car these days has a differential, making one side spin faster than the other in corners.

Besides, much more weight is saved with high-speed electric motors, because they have a much better power-to-weight ratio than low-speed wheel motors, and they're more efficient overall.

Despite that, a lot more weight will be unsprung, which hurts handling and ride quality a lot.

Not exactly what you mean but if you are talking about suspension that is simply not true, it jsut requires different techniques.

When a heavier wheel bounces from a pothole, the motion carries a lot more energy that has to be damped by the suspension. It jostles the car around much harder.

True, but cars are meant to drive mainly on the road. Also a decent suspension doesnt have this problem at all especially when there is no axis it effects the car less and just the local suspension, thus more energy efficient.

And the heavy batteries will void the weight advantage anyways.

Direct wheel motors or axis motor, the battery weight or position doesnt change.

And every car these days has a differential, making one side spin faster than the other in corners.

Thus losing efficiency in the differential.

Besides, much more weight is saved with high-speed electric motors, because they have a much better power-to-weight ratio than low-speed wheel motors, and they're more efficient overall.

I dont know the exact numbers to say anything about that but it would be an interesting battle to test this out in practise.

If you think unsprung weight doesn't matter to ride quality, especially in a small vehicle, you're not worth talking to.

iQ? better get in line...

hope they find a better name for the european market

Thus losing efficiency in the differential.

Less than 3%, depending on the differential. Much more is lost in having to use higher currents to produce power in a wheel motor.

The problem of electric motors is that their efficiency drops dramatically at speeds below about 20% of the nominal speed because of the high currents required to make power. That means, if you "gear" a wheel motor to go 100 mph, it will be really inefficient below 20 mph, and they struggle to produce power without overheating.

High speed motors aren't trying to produce much torque because the gears turn the speed into torque. That means the required magnetic field strenght is lower, less current is needed to produce it, the mass of the copper in the coils is smaller (fewer turns of wire), and the resistance is reduced, all leading to higher efficiency. High speed motors can also be run "overspeed" much higher than low speed motors because of the smaller inductance of the magnetics.

To really appreciate how much wheel hub motors weigh, you can take something like Ford's Hi-Pa Drive HPD30 which weighs 18 kilograms and produces 40 kW peak and 2000 rpm. (1:2 ratio between sustained/peak is typical unless extra cooling is provided)

High speed motors like CPM RFTR can do 50 kW (100 kW peak) and 6000 rpm with a weight of 14 kg, and with an efficiency of over 96% according to the manufacturer.

Adding 18 kilos to a wheel almost triples the moving weight that has to be damped by the suspension, which has a significant effect on the ride quality. It also puts more stress on the brakes because of the energy stored in the rotation of the heavy wheel.

I had a funny thought about the range. Any normal cars fuel guage would be in or almost in the red with only 60 miles fuel left in the tank.