THE AC EDGE!

Yes AC, as in Alternating Current, not air conditioning. It's what powers most of the electrical machines in your life and soon it's coming to a golf car near you. Long extension cord not required! This AC is a little different than what pulses through your home & work. AC systems for golf cars have been in development for about 10 years and now you can have one in your cart. It will change the way you think & feel about electric propulsion.

Here is how it works: The DC (direct current) power of a 48-volt battery pack is inverted to a 3-phase AC signal to power an 18hp, 3-phase, AC induction motor. The motor bolts right up to most golf car differentials and the entire motor & controller installation is pretty straightforward. Curtis Instruments, of Mt Kisco, NY, designed and built the special DC to AC inverter/controller combo. It is somewhat similar to the DC electronic speed controllers found in modern golf carts but it is a tad more complicated. It not only changes the DC to 3-phase AC, and back again for regen, it also controls the motor speed according to pedal position. AC delivers a lot of power under a load, like climbing hills with four passengers aboard, and it provides significant electric motor braking down to ½ mph. In other words, the speed of the car is proportional to the position of the pedal, uphill & down. Features like rate of acceleration, top speed, regen characteristics and the aggressiveness of plug braking are all programmable. The performance characteristics of AC are a leap above its DC counterpart, even given the regen features of modern DC motors & controllers. AC has been slow to come to the golf cart market because of the engineering & programming complexity of the inverter/speed controller and because of the cost.

COST:

Let's talk about the cost for a moment, just to get the ugly part out of the way first. AC is not for the faint of heart or for the frugal owner. The system requires a 48 volt battery pack and, therefore, a 48-volt charger. Folks with 36-volt golf carts will have to ante up a few extra bucks to create a 48-volt pack and also procure a charger (figure $500.00 for a new charger). The 48 volts can come from any battery configuration (eight 6s, six 8s or four 12s) as long as there is space to secure them in the cart (don't forget the bag well area, if you don't use the cart for golf). Not including the extra dough needed to upgrade to 48-volts, the AC motor, inverter/controller and cabling to install will cost about $2100.00 to $2500.00 plus shipping (the components weigh in at almost 100 lbs but they can be shipped UPS). This money does not include a 48-volt solenoid, the labor needed to install the system nor does it include any extra cabling that might be required because of a particular battery arrangement or the location of the controller. Don't forget in all this figuring that you get back your old DC motor, controller and, maybe, a charger, which you can sell to offset some of the upfront cost. Furthermore, if you are considering a major DC motor/controller upgrade, an AC system might not cost that much more. Depending on how you use your golf cart, the increase in performance will be well worth the extra dough. We built the largest 48-volt performance package you can buy (a 72-volt system is available—more below). Here at 3000 to 6000 feet of elevation in the Blue Ridge Mountains of NW North Carolina, USA , we wanted a system that could handle 4 people on a lifted chassis, pull up our steep hills with authority and yet provide significant downhill speed control by means other than the standard wheel brakes. We got what we wanted. For flatter terrain or less demanding conditions a smaller controller is available. The 18hp motor is standard.

WHY AC?

Actually your DC golf cart motor runs on AC, you just don't know it. The motor itself mechanically changes the DC to AC by means of the armature windings & the four carbon brushes that ride against the commutator bars, which are integral to the windings. So what's the big deal? The brush/commutator arrangement is inefficient & problematic. The carbon brushes are held against the spinning commutator by springs and this creates a weak connection for the transfer of high current. Weak connections anywhere in a DC power circuit result in heat & arcing and when severe enough total breakdown, e.g., a melted battery terminal caused by a loose cable connection. If everything is good the brushes do a fine job but the system is still inefficient and prone to failure, especially with sustained high torque/high amp requirements. True AC motors do not need this mechanical commutation apparatus to make the motor spin, but this misses the point. An AC induction motor has a fundamentally different way of getting the core (rotor) to spin. (NOTE: In AC motors the spinning core is called a rotor, not an armature (they are very different), and the outer field that surrounds the rotor is called a stator). Spin is magnetically induced as adjacent field coils, evenly spaced around the inside of the motor frame, are sequentially magnetized by the incoming 3-phase AC power. The metal core (rotor) spins trying to catch up with the rotating outer magnetic field but it never can.

What does all this mean? Simply put, an AC induction motor is more efficient than its DC counterpart by a factor of 20 to 40%, depending on the load. It creates a lot more torque, faster acceleration and since it has no mechanical connections, other than the ball bearings at each end of the rotor, maintenance is minimal. In short it is a simple, rugged and reliable design. Furthermore an AC motor is more receptive to electrical regeneration-it naturally wants to regen-and this helps with downhill speed control, which is one of the main reasons we are using it here. Another reason we considered an AC system is its ability to climb hills with a load. It pulls with speed & authority and maintains downhill speed limits. Available DC systems just can't deliver all these features.

WHAT YOU GET:

This AC system comes with an 18hp induction motor that develops 81 foot pounds of torque, delivers 6000 rpm and may be configured to have a top speed of 25mph or less. The DC to AC inverter/speed controller is included and it is available in 350amp, 450amp and 650amp versions. A fairly large aluminum heat sink to mount the controller & solenoid in the car is included. As are all the small control wires to connect everything. A golf/street switch (hi/low speed selection), a momentary ‘menu' button (for programming), and a cool 2” dash mounted speedometer/tachometer/charge indicator gauge all come too. The system requires 2-gauge battery cables throughout. A complete set designed for the intended vehicle may be purchased for $65.00. You may need extra 2-gauge cables depending on what battery configuration you decide on & where they are placed in the cart. A main power fuse is included but we recommend also installing a main battery cut off switch in case some other problem requires total shut down (with the key off, there is no parasitic draw placed on the battery pack, unlike DC regen controllers). You will need to buy a 48-volt solenoid if you don't already have one. Our 48-volt Albright solenoid offered online is recommended.

I mentioned above that the AC controller is a little more complicated than its DC counterpart; think of building a house vs building a skyscraper. The DC controller has about 50 different hard programming parameters whereas the AC has about 150. Some personal settings can be selected through the Menu Button and many other settings can be changed with more sophisticated equipment and software, costing upwards of $500.00. We need to know what brand & year of car and what kind of throttle input your car uses in order to provide you with the correct system to meet your needs. Curtis Instruments has been working on this controller for 6 to 7 years. The motor manufacturer (not Curtis) has over 3 years invested in developing & perfecting the AC motor compatibility with the controller functions.

A FEW PRECAUTIONS:

The optional 2-gauge battery cable set uses copper terminal ends and each is swaged 3 times for a very positive crimp. Should you need to make extra cables, copper terminals are better than some of the other ‘dipped' ends and proper crimp technique is essential. Lead solder may be used but it actually creates additional resistance to the flow of electricity through the crimp. Crimping must be done correctly and this requires a special tool made to properly crimp a specific size terminal end to specific size cable. Don't beat the end with a chisel or a hammer, as I have seen so many times over the years…never a good method! Routing the 2-gauge cable around & through the chassis to connect everything must be well planned. No routing around sharp corners or through holes in the frame unless proper protection from chafing is used, and don't stretch any cable to reach that extra, unanticipated, inch or two. Use wire ties and cable loom if needed. Pay extra attention to the proper tightness of the cable connections on the lead battery posts. 100 to 105 inch pounds of torque are recommended. Battery posts must be in good condition. Trust me: hot spots and poorly routed cabling will very definitely come back to haunt you. Custom cable sets can be made to order to ensure proper crimp technique.

LET'S GET GOING:

Plan Ahead:

First thing to do is go raid the cookie jar so you have enough dough to do all this. Next, decide how you are going to use the car after everything is done. The cars we have built here employ eight 6-volt batteries with 2 placed in the bagwell. We wanted all the capacity we could get but six 8s are fine and they will fit in the battery racks already in the car. If you just want to get to the course or around the community a little faster or go further, and the car is not lifted, the 350amp controller will suffice. If you want to carry four adults around fairly level terrain with maybe a few hills, with or without a lift kit & oversize tires, then the 450amp controller will be suitable. If you want a hoss that is going to provide adequate torque & speed for steep hill pulls, heavy loads, lifted suspensions, etc., then go with the big daddy 650. Eight 6-volt batteries are going to provide more range than any other configuration but you need a secure place to put all that extra lead—plan for it.

The Charger:

You will need a 48-volt charger. We offer an on-board Delta-Q high frequency, switch mode charger (see pix) that charges the batteries 30% faster with 20% more efficiency. It is no small thing (12” L x 10” W x 4.5” D) and it should be installed such that you can see the LED status lights on the side of the charger. We built a custom wedge-shaped bracket to fit on the driver side of the battery pack such that the LED readout on the end of the charger is easy to see. The charger must terminate to a flush mount AC male receptacle (usually installed in the seat wrap body panel) that accepts the female end of a standard extension cord (25 feet, 12 gauge is suggested). This male receptacle is not included with the charger. Or you may want to opt for a regular stay-at-home charger, which we can also provide at a cost about the same as the Delta-Q…$500.00. The 48-volt Club Car or Yamaha charger will work fine. If you opt for the on-board D-Q then you can also remove the On Board Computer (OBC) from your Club Car. The advantages of an on-board charger include opportunity charging wherever AC is available, not having to tote a heavy charger around and, since it is bolted into the car, theft of the charger is difficult to say the least.

The installation of the on-board D-Q 48-volt charger is not complicated. You will need a flush mount 120-volt AC male receptacle to be placed where it is convenient to plug in an extension cord (12 gauge, 25 feet long) to power the charger. Many boat, travel trailers & motor homes use similar receptacles for AC connection at the dock or campsite. We used the hole in the seat wrap, just behind the drivers left calf, where the original factory charger receptacle was placed. The golf car industry uses different DC plug configurations for 36-v and 48-v chargers so one cannot be mistakenly plugged into the other. We certainly recommend you follow this guideline should you use a regular stay-at-home charger.

Installation:

Remove your batteries to make room to work. With a Club Car you will probably want to remove the rear body for easier access to the motor & controller. Remove the existing motor, solenoid and controller, and all of the cables and control wires (except the OBC, if you are going to keep it). Ev1erything you need comes in the AC package except the 2-gauge cables. The F/R toggle switch, the dual speed switch (golf/street), the menu button and the unique 2” dash gauge (mph/RPM/charge indicator) are best installed in the dash for easy viewing and access. The control wires powering these components will need to be carefully routed to the front of the car & secured behind the dash.

The AC inverter/controller is much larger than your existing one, plus it comes with a large aluminum mount plate that must be firmly attached to the frame of the cart. The controller & the 48-v solenoid will attach to the plate. The motor bolts right up to the differential mount flange but it is larger & heavier than the original…assistance may be needed. Working room may be pretty tight, depending in which car you install this system, so loosely attach all the power cables you can and then place the batteries. Allow plenty of cable but not too much…remember, don't stretch them. If everything fits as planned, tighten it all down. Use battery hold down brackets with proper J bolts. We suggest protective rubber booties over the open cable connections on the controller & solenoid, and it's not a bad idea for the main battery posts too. These rubber terminal protectors are not included. The main battery cut-off switch, if used, should be mounted in an easy-to-get-to place. The main cut-off switch is not included with the package but we do offer one in our catalog.

The Cool Multi-function Dash Gauge and Switches:

The dash gauge toggles between 5 different display functions; state of charge, total battery volts, rpm of motor, mph of car and TOC (this means time the controller has been in use since the last charge). It also displays ‘Golf' when you are in the slower ‘Golf' speed setting (typically 15mph) but you can toggle through the other functions by pushing the ‘Menu' button. When in ‘Street' speed, the gauge automatically displays the miles per hour but again you may toggle to see the other displays. The single row of lights at the bottom of the gauge approximates the state of charge in the batteries. The digital display gives an exact readout.

More than likely you will want to install the Speed Selection Switch, the Menu Button & the 2” gauge in the dash. They don't take up a lot of room but plan carefully; once the holes are cut they will be hard to undo. The Menu Button is a momentary push button switch that also is used for the initial programming required to set the needed parameters for the controller to work in the specific car. Instructions are included. You are now ready to rock!

A Few Installation Notes:

The AC controller is larger (12 x 9 x 4) than a conventional regen controller and it must be mounted on the included aluminum heat sink. There is plenty of room on either side of the battery pack in the E-Z-GO Medalist & TXT models (1994 and up). The AC motor will bolt up to any Dana H-12 differential including E-Z-GO back to 1988, Yamaha back to 1993, Columbia ParCar from 1990 and Melex from 1992. The Dana H-12 is a very popular and durable differential found in many electric vehicles. A motor is available that will bolt up to the Graziano and Kawasaki rear ends on Club Car DS models. You will probably want to remove the rear body on the DS for more working room. In the new Club Car Precedent there is only enough room for the smaller 350amp controller and a special kit may be ordered for easy installation. On some Yamaha models the rear upper shock mount bracket may need to have a small part cut away to permit the larger AC motor to fit.

The 72-Volt System

This is an animal that requires a 72-volt battery pack; twelve 6s, nine 8s or six 12-volt batteries. This is a lot of lead that takes up a fair amount of space but if your requirements demand this kind of power it is available. It is designed for larger and/or heavier vehicles carrying extreme loads such as 6, 8 or more passengers or burden carrier-type machines. The AC controller is rated at 550amps the motor is rated at 22.5hp and it delivers 110 foot pounds of torque. A 72-volt charger is needed and the on-board Delta-Q charger mentioned above is available in a 72-volt design for $500.00. The cost of the AC controller, motor and control wires, gauges, buttons and all price out close to $3000.00 plus shipping.

LEGAL CONSIDERATIONS:

If you are thinking; Oh boy, I am going to buy one these babies, set the top speed to 25mph and have my local mechanic install it! WHOA! STOP! WAIT! In order for your local mechanic and/or dealer to legally build a vehicle that goes faster than 19.9mph they must be registered with the state & federal governments to be licensed as an automobile manufacturer! That's right, because that is what you are building; a car that can be registered with the state and be driven on public roads with speed limits of 35mph or less. The NHTSA Rule 500 makes the break at 20mph for ‘golf cars', and above 20 but no faster than 25mph is a NEV or LSV (Neighborhood Electric Vehicle, or Low Speed Vehicle, as the feds call them), which is a motor vehicle with a long list of safety requirements. The hardest one to meet is that pesky 17 digit Vehicle Identification Number (VIN) the gov wants to see on all ‘motor vehicles' registered for use on public roads. If your mechanic or local dealership gets caught making a motor vehicle without proper credentials, they are subject to some pretty hefty fines and you may be too. Should you cause an accident involving personal injury with an illegal motor vehicle on a public road, you had better get a lawyer.

I hate to throw cold water on big plans. There are ways of getting around some of these issues. If you only use the vehicle on private property, off road, away from public thoroughfares, or you make the vehicle yourself, then some of these regulations are mitigated. If your intent is to ride to and through town perhaps you will be better off purchasing a Columbia ParCar, Western, or GEM. All of these companies are, or very soon will be, offering AC systems in their LSVs. There is no question some small dealerships are skirting these federal regulations, either due to ignorance or brazen lawbreaking. In recent years the demand for bigger & faster golf carts for on & off road use has been tremendous. The motors & controllers are already available to meet that demand with DC components, and now with AC power, with a little more cost. We have heard about dealerships even putting made-up VINs on the car to hoodwink the buyer and/or the local law enforcement. For your own protection, ask to see the federal & state docs from the company owner where you intend to have your golf cart modified to go above the 20mph threshold. If he tells you one is not needed, go elsewhere. There are very different requirements to be a golf cart going 19.9mph and one going over 20, when used on public roads. Be careful!

Keep in mind that only 31 states currently have laws on the books permitting use of LSVs on roads with 35mph speed limits. To check on the laws of your state click here: www.electricdrive.org.

A Little History & Background:

Golf cart drive systems closely follow fork lift and locomotive technology (train locomotives have a huge diesel powered generator that feed a series of large AC motors located at the wheels). If an industry needs to move heavy loads efficiently they will invest in the best technologies for the long run. Electronic speed controllers were used in fork lifts for years (they were called silicone controlled rectifiers, or SCRs) before they became common in golf carts. Once the cost of these DC motor controllers came down to acceptable levels (about 1990) they went into golf cars. They quickly became standard equipment throughout the industry. Early on the motors remained the same as they had always been--series wound--which basically means the same amount of amps that go through the armature also go through the field. In 1995 the motor & controller technology evolved to where the amps running through the field could be different than the amps running through the armature.

This kind of motor is called a ‘SepEx' ( Sep arately- Ex cited) motor. This new motor design allowed for ‘field weakening', which provides a way to make the motor spin faster and use less battery power once the start-up inertia is overcome. It also permits the motor, while coasting, to create a charging voltage that goes back to the batteries. While the recharging ability of the motor is pretty minor, in effect it allows for the top speed of the car to be automatically controlled, no more lickety-split down the hills. We call this phenomena ‘regenerative braking', or, more simply, regen. The SepEx motor & its regen controller talk to each other; when more torque is needed the motor field is strengthened, when less torque is required the field is weakened and while coasting at a certain speed a regen voltage is sent to the battery pack, which creates an electronic braking effect on the car. The regen controller & motor is a couple; they are designed to work with each other as a pair. The SepEx motor armature is very much like its series wound counterpart, but its outer field is very different. Instead of field windings the size of a skinny pencil, as in a series motor, the SepEx field windings are more the thickness of a paper clip and there are a lot more windings.

So what's the matter with this great DC system? It primarily involves the DC motor and the four carbon brushes that ride against the commutator, which is an integral part of the spinning armature inside the motor. As the name suggests, the commutator and the brushes constantly, and very rapidly, switch the direction of the incoming DC current to mechanically make AC. This commutation creates a quickly changing magnetic field in the armature making it ‘chase' a magnetic field in the outer windings of the motor. The attraction/repulsion of the changing magnetic poles is what makes the armature spin.

OK, OK I am getting a little technical here and there are far better explanations of motor theory and application than I am capable of producing. Check out these great websites if you have further interest in motor theory: www.eatonelectrical.com and www.reliance.com/mtr/mtrthrmn.htm .

Suffice it to say the DC commutator & brush system works quite well & is cost effective but it is very inefficient and brush/commutator problems have been a way of life. AC motors do not use a commutator or any brushes at all because alternating current switches direction naturally so it doesn't need an elaborate method to create the switching effect. In a DC motor the armature does the switching mechanically. An induction motor depends upon an electrically rotating magnetic field, not a mechanically rotating one. Outside of the bearings at each end of the spinning rotor there is nothing to wear out or give problems. Simple yea?

Other References of Interest:

For a deeper understanding of AC development, perform a Google search on Michael Faraday (discovered how magnetic fields work in a conductor and can be applied), Francois Jean Arago (uncovered the properties of induction in 1824), Heinrich Rudolf Hertz (artificially created electromagnetic waves in 1888, which eventually lead to all kinds of things wireless) and Nikola Tesla (made the first workable AC induction motor in 1887 and laid the groundwork for modern day power generation and the motors that use that power), or click on this link for lots of biographies of major figures involved in making our electric world: http://www.phy.hr/~dpaar/fizicari/allindex.html .

For more info about electric locomotives:

www.railfanclub.org

(Exclusive to GolfCarCatalog.com) copyright January 2006