Motors and Controllers; Why So Expensive

[gone7]

As I have been looking at electric vehicles, it appears that there are couple foundational issues keeping the rest of us from being able to get into electric vehicles. They have to do with the cost. I can't imagine many people being able to buy a fifty-thousand dollar electric vehicle from some major manufacturer, especially when it only goes fifty miles on a charge. On the other hand, I can imagine many people, even in the lower, poor working-class, who can build their own. That is, if they can afford and obtain the parts. There lies the rub.

So we have two very important questions:
1. Since we have been using and perfecting AC motors for over one hundred years (since started by Tesla at least), why are automotive-use AC motors so expensive?

2. Why are the controllers for them also so expensive?

Please address your answers to these two questions alone. And thank you for your input.

[oil pan 4]

The motors are typically designed just for that vehicle.
The motor controlers are buit just for that motor.

Why not go DC for like 1/2 to 1/3 the cost?

There is a lot of off the self and a lot of aftermarket support for DC motors and motor controlers.
If I was going to build an electric vehicle I would never even consider AC.

If I remember right AC offers like a 10% range advantage over DC. Why not take the money saved on the drive system and put it into buying or building a bigger battery and get more range over all?

Pretty much all the hobbiests use DC and if you start shopping around for parts you will see why.

[mechman600]

Well said. If you spend the same amount of money on a DC system as an AC system you will also have the luxury of being able to smoke your tires at will.

I would argue that EV money is best spent on a wicked DC controller (Soliton, Zilla, etc.), a huge lithium battery pack and a nice, powerful charger.

One day I will know what that feels like.

[oil pan 4]

I only know that because I drew up plans to build an electric/rubber burning S-10 and got a nearly free late 1990s S-10 with a blown engine.
You can get an insanely powerfull DC electric motor for a few grand, when I mean powerful racers used aceleration calculations to put the peak horsepower some where around 2,500.
You can spend a little less if you dont need 2,500 horsepower.

When you need raw power and torque DC is where you need to be, I have a modded electric chain saw ran off a 220v varrac (it flips standard 20a 110v single line circuit breakers) that out cuts 4 horsepower gas saws with ease and it uses a DC motor.
The only draw back is it cant go very far into the woods, thats it.

[serialk11r]

oil pan 4 is right, DC motors are cheap and controllers can be found pretty cheap too if you look in the right places. Depends on how much power you want.

Hell, brushed DC motors can be 93% efficient, you'll need one hell of an AC motor to have a significant improvement over that. I'm not sure why AC motors are used but it probably has to do with the fact that they can hold speed easily, and I think regenerative braking is easier to implement (not sure on this one). I'm guessing it's a controller thing.

If you want very high power in a small package you can buy RC airplane motors with 20hp peak power that weigh like 5 pounds. Decent controllers can be had for low hundreds. If you take the cheaper RC airplane motors, maybe add beefy bearings, hall effect sensors, and put one on each wheel of your car, you'll have a good amount of power on tap.

[gone7]

A little off-topic, friends, but thanks anyway. The best mileage will always be AC, particularly because of regen braking and lower maintenance.

[serialk11r]

Originally Posted by ACEV

A little off-topic, friends, but thanks anyway. The best mileage will always be AC, particularly because of regen braking and lower maintenance.

Uh, DC controllers can have regen braking, and maintenance probably depends on commutation more than AC vs. DC...not sure why you're trying to draw those conclusions.

[oil pan 4]

AC gets better milage, we know. Its also 2 to 3 times the price and you cant get hardly anything off the shelf for building one.
How about this, if you make a one off AC drive system and some one puts it together for you what are you going to do when something breaks?

If you run DC then you have lots of options, get a bigger, better or up graded part when one fails. DC systems are easy to make scale able and are very forgiving, you can mix and match motors, controllers, battery configureations as long as you stay under the max input voltatage for the controler and dont over load the controler or motor.

If you have an AC system and one battery goes bad (say you are using 6 or 12 volt lead acids) I don't think you can just bypass the bad batt. With a DC system you bypass/remove the bad battery and keep going with slightly reduced voltage and preformance.
I dont think an AC system can do that.

I don't see why changing the brushes once every 6 months to 2 years is such a big deal.

If you want more power/range build a generator trailer or build a pickup so the generator can sit in back when you need it.
I bet you can rig up a DC set up with a generator and unlimited range cheaper than you can build an AC setup with regen braking.

Unless you are going to contract a motor builder and motor controler company for a minimum order to start producing vehicles then there is no reason for the hobbiest to try to build an AC system form the ground up.

[Ryland]

How much are A/C motors and how much are the A/C speed controllers?
The A/C motors I've seen either are not sized for a car or are made in such small numbers that of course they are going to be priced high!
The D/C motors that are out there are made in huge numbers, NetGain motors are as cheap as they are because they are a special run of Warfield forklift motors, more or less the same motor but with nice output shafts and different brushes.
At one point in time Fiat, or maybe it was a company converting gliders to electric, were going to put a 3 phase forklift motor in the Fiat 500, we don't really have 3 phase electric forklifts here but when an automaker is realizing that they might be better off leaving some of the parts outsourced it really makes you wonder.

[gone7]

Ryland, are you implying that DC is cheaper only because of volume made? Would the $8000 AC come down to $800 if they made a thousand instead of three?