HOW ELECTRIC VEHICLES WORK

Now that we've figured out all the problems of global energy generation and distribution, let's take a look at how electric cars like the ZENN actually work.

Electric cars are really pretty simple:  there are a bunch of batteries to supply the power, a motor (or several) to use that power to move the car, and a controller to let you control the speed and direction of the car.   Oh, yeah - there is also a charger to charge your batteries from your electric socket.

 As usual, the devil is always in the details, so let's look at these components one by one.

MOTORS

 As already alluded to, electric motors are fairly simple and mature technological beasts.  Basically, they use the force of electromagnetism to turn a shaft with enough power to move the car.  Motors can be designed to run on either a DC (direct current) source or on an AC (alternating current) source.  There are advantages and disadvantages to each.

Batteries supply DC power only.  Therefore, using a DC controller and a DC motor represents a very simple design.  This is way the base-model ZENNs are designed and delivered from the factory.  This is also the way most golf carts and electric forklifts are designed.  It is a simple, dependable system that has served well over the years.  It is also less expensive than other designs.

The motor in the ZENN is a 5 horsepower DC electric motor operating on 72 volts DC (often abbreviated VDC).  This motor was considered adequate for the 25 mph limitation placed on the ZENN by the federal government.  I can attest from driving a stock ZENN that the car accelerates to 25 mph very reasonably and maintains that speed easily on flat terrain.  If you want to achieve a higher top speed, or accelerate faster, or climb hills fast, it will probably be best to replace the stock motor with a more powerful one. 

BTW, it should be noted that "electric horsepower" is not really the same as the horsepower rating of your current car.  While there is a _theoretical_ equivalence, in the real world 1 "electric horsepower" is far more efficient at moving a car than 1 "ICE horsepower". (I've forgotten the practical conversion factor, but I'll try to look it up).  Therefore, a 5 hp electric motor seems far more powerful than a 5 hp ICE - like the one on your lawnmower.

There are easily available DC motors ranging from 7.5 hp up to about 18 hp.  The smaller ones will (I'm told) fit into the ZENN pretty easily.  The larger ones will fit only with extensive custom work. 

DC motors come in two flavors;  brushed and brushless.  Brushed is the older, original technology.  This design uses a mechanical device called a commutator to keep the electromagnetic fields moving around so as to make power and rotation.  The commutator spins and the power is sent to the armature windings through a set of "brushes" that are actually solid bars of a conductive material.  This system works just fine at lower RPM and power - but as either increases this mechanical switching becomes inefficient at getting the large amounts of power necessary to the right places at just the right time.  Because the brushes are in physical and electrical contact with the spinning commutator, they wear out and also arc between commutator segments.  A better system was needed.

The brushless DC motor uses a little computer called a controller to get the electrons to where they are supposed to be.  The brushes and commutator are, thus, replaced and efficiency is increased.  Brushless DC motors can make more power and higher RPM than brushed motors - all else being equal (which it never is, of course).

Finally, there are AC motors.  Like brushless DC motors, AC motors use controllers instead of commutators.  They are even more efficient and powerful yet.  However, they often require higher voltages and more complex (read costly) controllers.

An electric car can have a single motor under the hood, or so-called "hub motors" built into each wheel.  A Japanese researcher has prototyped an 8-wheeled electric car using hub motors that has achieved 230 mph on a circle track - and is aiming at the ICE land speed record of 250 mph.

BATTERIES

The "gas tank" in an electric vehicle is its batteries.  The more stored electricity, the greater speed and range are possible.  But as mentioned previously, the best current batteries are still just barely able to do the job.

The batteries in most electric cars are much like the so-called "flooded lead-acid" batteries in your car now - there are just more of them.  Each is usually 12 volts DC, so when they are hooked up in series, their voltages add up.  This is nice, because higher voltages allow more things to be done with more efficiency. 

As mentioned before, the XENN uses 6 12VDC batteries hooked in series to create a 72 VDC system.  The stock batteries are so-called "gel cells", and the upgraded Discovery batteries are known as AGM batteries where AGM stands for "adsorbed glass mat".  Like "flooded" batteries, all these battery types use a type of acid and metallic lead to store electricity.  That makes them quite heavy. 

A newer type of battery that is known as lithium ion or lithium polymer is available and it stores much more energy per pound that the lead-acid type.  Lithium batteries also charge and discharge faster than lead-acid batteries.  Unfortunately, they are more expensive and some types have a nasty habit of spontaneous battery combustion at 3500 degrees!  Some experts say that this makes lithium batteries completely unsuitable for electric vehicles.  However the current darling of the electric car world - the $100,000 Tesla Roadster - uses over 6000 lithium batteries to power it from 0-60 in 4 seconds and to a top speed of 130 mph.  If Teslas start spontaneously burning up, we'll know "the experts" were correct!  My worry about lithium batteries comes from the possibility of impact  like in an accident.  Simply beating them up can cause lithium batteries to start burning.

The AltairNano battery is supposed to be a type of lithium battery that is immune from what the engineers politely call "thermal runaway" (meaning that whole 3500 degree fire thing).  These superbatteries will be powering the Phoenix Motorcars electric vehicles supposed to be delivered in 2008.  I had my name on the waiting list for a Phoenix sport utility vehicle, but took it off when I bought the ZENN.  I sure wouldn't mind getting my hands on about 6-8 of those Altair batteries, though!

CONTROLLERS

Although up above I may have given the impression that brushed DC motors don't _require_ a controller (which is true, as far as that goes), ALL electric vehicles require some kind of controller to control speed and direction.  Therefore, even though the ZENN comes stock with a 5 hp brushed DC motor, it also has a General Electric controller in it.  Right now I don't know the exact model of the stock controller, but I'm trying to dig that up.  The controller, remember, is a little computer that controls the motor.  As a computer, it can be programmed - and re-programmed!  There is GE software called "Sentry" that accomplishes this trick.  It is also the controller that limits the ZENN's top speed.  Therefore, it is possible - at least in principle - to reprogram the GE controller to permit the ZENN to get to 35 mph as allowed in MT and WA.

Apparently, a number of folks have already done this, but with mixed results.  In order to get 35 mph in this way, the controller has to run the stock motor faster than it's designed for.  This has burned up a motor or two, I'm told.  But others have worked OK.  If replacing an $800 motor is no big deal to you, you can try this method.  Complete instructions can be found on a really cool website with the memorable name;

                                     www.electric-cars-are-for-girls.com

In order to reprogram your controller you will need a copy of the GE Sentry software (version 4 or later), a PC-to-controller patch cable, and a file with the new values to set.  How to come up with these things is explained on the website.

GE is not the only company that makes controllers, BTW.  Curtis and Alltrax are others I've come up with.  There are probably more.  These things are mostly used to control electric motors in golf carts and fork lifts, but they can be adapted to electric street vehicles pretty easily (I'm told).  A totally new controller will run you $700 - $1000.

Like the motors they control, controllers come in two flavors;  DC and AC.  Obviously, you need to have the correct one for your motor.

One more thing:  the controller also handles a nifty little thing called "regenerative braking" or "regen".  This feature allows you, when braking, to reclaim some of the energy you've used to get up to speed.  It does this by making the drive motor act like a generator for a while.  Regenerative braking can add about 20% to your range - on a good day.  Contrary to what I've read, both AC and DC systems can have regenerative braking.  It's just more common on AC controllers.  The stock GE controller on the ZENN features a programmable amount of regen - and you can definitely feel it.  When you take your foot off the accelerator, the ZENN immediately feels like it's braking a little, even though you are not applying the brakes.  This is just the regen feature running the electrons backwards through your motor and back into the batteries.  I guess that on a long downhill, it might amount to quite a bit.

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