An Electric Mule

Michael Hackleman

©1994 Michael A. Hackleman

On the Hilo side of the big island of Hawaii, more than 250 inches of rain fall each year. On a large sustainable organic farm, Harry MacDonald manages the production of Awapuhi for Paul Mitchell Systems (one ingredient in their hair products). On the hilly terrain, only one vehicle can haul compost and deliver machinery for maintenance without breaking up the fragile turf. An electric mule.

The mule is an electrified 2WD Kawasaki 500 Mule. Having worked on the Mana La project and a variety of electric utility vehicles, Harry was well aware of the potential of EVs in farm work. Harry also runs the Harley Davidson shops on the big island (in Hilo and Kona). When a Kawasaki Mule ended up at his store, Harry called in Tom Carpenter to assess its potential as an electric.

Tom Carpenter is no stranger to electric propulsion or offroad vehicles. With a background in marine electronics, he once maintained four electric boats, each a 24 foot bay launch owned and operated by residents in Newport Harbor. Also, Tom owns a 1952 Austin Champ, a 4WD British military vehicle built by Rolls Royce. With an estimated 40 Austin Champs remaining in service worldwide, maintaining his vehicle has been a challenge!

Standing alongside Harry in his shop, Tom sized up the Kawasaki Mule. "The first thing I noticed," Tom explained, "was that, with the engine and infinite ratio transmission removed, there would be adequate space for batteries. The second thing I noticed was the flatbelt drive of a Harley Davidson Softail sitting next to the Mule. My experiences with the belt drives of the electric launches were good. They were reliable and quiet. The combination was clearly going to work."

Homemade Thermoelectric Power

Above: Tom Carpenter rides the silent, non-polluting Mule down the beach.

The Conversion

With a thumbs up from Harry, Tom set to work. First, he contacted Ken Koch at KTA Services and ordered the parts he would need for the system the two of them designed. Next, he removed the engine, transmission, and engine-related components. Tom welded together a 3/8 inch aluminum motor mount, fashioned to bolt to the original engine mounting holes. When it arrived, the 6 hp series Advanced DC Motor (A89-4001) was bolted up. Since the locking differential of the Mule has an internal 6:1 ratio, Tom opted for a 1:1 ratio of the timing belt pulleys.

There was room for six batteries in the Mule, five in the rear and one under the single front seat. Would the batteries be 6 Volt or 12 Volt? Since the vehicle was intended for farm work, rather than recreational or street use, Tom opted for six 6 Volt deep-cycle batteries, or a pack voltage of 36 VDC

A Curtis 1205-201 controller, rated 36-48 Volt and 350 Amps, was purchased. The controller's PV-6 pot box was connected through the existing throttle cable to the foot pedal. The locking differential allowed a mechanical Forward and Reverse, so no electrical reversing was required. A DC contactor (Albright SW-180B) was selected for key switch operation. The vehicle's original 12 Volt auxiliary battery was replaced with an isolated DC-DC converter (Newmar 48-12-12I, 20-56 VDC input, 13 Amp peak output). A dual main circuit breaker (GE, TQD150) was added to isolate the battery pack from the vehicle for servicing.

With a wet climate in mind, Tom installed the controller, contactor, pot box, meter shunts, and a 12 VDC fuse strip inside a plastic Carlon box. An outdoor timer box, mounted under the front seat, houses the circuit breaker within easy reach of the driver.

The Battery Pack

Tom selected sealed, absorbed-glass matte, deep cycle batteries for the Mule. Used in wheelchairs and other motive power applications, the Concorde 6 Volt batteries weigh 68 pounds each, are rated at 180 Amp-hrs (20 hour rate), and use lug terminals.

To support the five batteries, Tom fashioned an aluminum frame from 1 1/4 inch aluminum angle and pop riveted it together. The sixth battery of the pack is mounted on the metal floor just under the front seat.

Solar Charging

The Mule is strictly solar-charged. Originally, it was designed to recharge from one of the three solar energy stations located on the 67 acre Awapuhi farm. Each station is composed of a dual-axis tracked solar electric array (15 Solec S100s), a battery pack (24 VDC, 1400 Amp-hr capacity), and an inverter (4000 watt sine wave Trace 4024, 120vac). Tom, who has a solar installation business, designed and installed the stations. A K&W charger (120 vac input, 24 VDC output) was purchased to recharge the Mule's batteries. Once pressed into service, the Mule's role was suddenly expanded. An alternate charging system resulted.

The Mule's Work Day

The Mule's steady work is hauling compost around the farm. The four foot square flatbed is designed for dumping, and tilting to drop its load. A drop-pin hitch secures a trailer that adds an additional 0.5 cubic yard of capacity.

"The electric Mule is the ideal vehicle for this hilly terrain," says MacDonald. "The road is dirt and loose gravel, but the turf is fragile and slick when wet. This job calls for strong torque without tire spin."

Occasionally, the mule does other work. One job is transporting the mowers and weedwackers to work areas. Another is hauling a 5000 watt generator to various work sites when power tools are needed. When a new building was planned, Tom had a different idea.

"I thought it would be interesting to use the Mule as a power source," he explained. "I attached a quickrelease plug to a Trace inverter (36 VDC input, 120 vac output) to tie into the battery pack. This proved ample for powering the tools."

Electric Mule

Above: There's plenty of room for the Mule's electric motor and drive train.

Since the Mule would be sitting all day at the building site, Tom decided to install three 100 Watt Solec panels on the Mule's roll bar assembly. In bright sun, the 6 Amp charge rate was just right, keeping the battery pack topped off despite the constant drain of power tools through the workday. "The silent ac power was an instant success with the work crews," Tom reported.

Sealed batteries are sensitive to overcharge. To limit the charge rate to a maximum of 2.2 Volts per cell, Tom added a charge controller, a Heliotrope CC-20, between the panels and battery.

"We've gotten into the habit of parking the Mule on any slope that tilts the panels toward the south," Tom explained. "That maximizes the charge rate. After four months of continuous operation, we have yet to plug the Mule into one of the solar stations."

Instrumentation

Several instruments were added to keep tabs on the Mule's new power plant. A dual-scale ammeter measures up to 500 Amps in propulsive power and 50 Amps for 12 Volt functions. A 0-50 VDC, sealed

Speed Controller

Above: Michael tests the Mule's performance. With the battery pack located so low in the vehicle, this EV felt stable on the rock jetty at the beach.

military surplus meter lets the driver monitor either the 36 Volt or 12 Volt system.

"The instruments are useful during the learning curve," Tom said, "but I won't install them on my next prototype. I'd rather use something simpler, like an Ananda Smart Light." The Smart Light is a three-color display that, through steady or flashing lights at various set points, tells the battery's state of charge.

A cycle computer, a VELO, was added to watch vehicle speed, distance, and time. It also recorded the maximum speed and accumulated distance. The magnetic sensor was glued to the left rear wheel, the magnetic pickup was secured to a brake line, and the computer was calibrated to the tire's circumference.

The First Run

How was the first trial run? "I charged up the batteries and selected a gravel road with rolling hills," Tom said. "I went 35 miles before I got low. The average speed was 13.8 mph. My highest speed was 27 mph. That was definitely downhill."

After a recharge, Tom added two additional 6 Volt batteries, strapping them down to the rear bed. With the pack at 48 VDC, Tom tried again. "The batteries went flat at 35 miles again, but the average speed went up to 17 mph."

The Bottom Line

What did it all cost? Battery pack: $600. A basic conversion kit: $2,160. The DC-DC converter: $190. Miscellaneous hardware and aluminum angle: $250. Tom estimates that it took him 30 hours to convert the mule. "A duplicate," Tom said, "would take only 20 hours."

What's Next?

Tom is tempted at this point to build a 4WD offroad vehicle from scratch. I have talked with him about teaming up to build something for use at Home Power's homestead. We've identified some of the component subassemblies and this design is still in the works. What if it were another conversion? "A 4WD Kawasaki Model 1000 would be my first choice," Tom replied. "These are solid machines. They're tough enough to handle the electric motor's low end torque. I'd push the pack voltage to 72 Volt, too."

Access

Author: Michael Hackleman, PO Box 63, Ben Lomond, CA 95005

Tom Carpenter, HCR 5201, Keaau, HI 96749

We're shipping sine wave inverters as fast as we can. The demand for this new series has resulted in record breaking sales! Our shipping department is packed with orders and sales for our standard units are at an all time high. Working overtime is helping and we are catching up.

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We're shipping sine wave inverters as fast as we can. The demand for this new series has resulted in record breaking sales! Our shipping department is packed with orders and sales for our standard units are at an all time high. Working overtime is helping and we are catching up.

If you have an order on the way, we want you to know that there may be a bit of a delay. There is only one choice in inverters and a whole lot of you made that choice at the same time. All of us here at TRACE want you to know that WE'RE SHIPPING like never before. After all, good things are worth waiting for.

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Responses

  • bernd
    How to replace throttle cable on a 1000 mule kawasaki?
    8 years ago
  • Sesuna
    How to convert kawasaki mule to electric?
    7 years ago

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