Updated: 05/31/02
In the Fall of 1996 I bought a Meyers Manx body that was almost like new. It came with a rolling chassis that was part of an earlier buggy. The taillights and hood had been installed and that was about it. It had been sitting for about 16 years. The body is a high quality hand laid item. This was the basis for my car to be.
I was either going to go with a 2 cylinder industrial ICE or electric. After some research I decided on electric and located some older but unused components. I wanted some experience before getting too far into the project so I did a lot of research. I decided to build a small scooter first. You can read about it in the scooter section.
I purchased a second hand (though unused) motor and controller. The motor is a 9" Advanced DC. The Curtis is a 1231C 96-144 volts and 500 amps. I originally wanted to use 12 x 6 volt batteries in a 72 volt car, but the good price on the motor/controller convinced me to go with 12 x 12 volt batteries in a 144 volt car. I would trade some range and economy for more performance.
Contrary to what most knowledgeable EV people told me, I decided to discard the clutch. My rationale was: You don't need a clutch to stop and start, and that is the reason cars have a clutch. The car will only weigh 1800-1900 pounds including batteries, so even a high gear will give adequate acceleration. The power curves for the motor showed that I would not have to shift on most around town driving, and maybe once at freeway speeds. The VW has a strong transmission and should hold up to shifts without the clutch. There is no flywheel so the motor cooling fan should provide enough drag to slow the motor for upshifting.
I had a motor adapter and coupler insert machined at a local shop, Next Intent. The insert was a case hardened segment splined on the inside and keyed on the outside. It fit inside a shaft coupling that clamped on to the motor shaft. I mounted a magnetic pickup on the coupler for my Westberg tachometer. I cut the pilot journal off the end of the transmission input shaft since it was not needed anymore and this allowed me to make the motor adapter plate almost an inch thinner. The plate is machined out of a single billet.
The above image shows the motor mounted and surrounded by the rear bumper cage.
I did a little a research on battery chargers and decided that I could make my own lightweight on-board charger. This worked out since I had decided on a 144 volt battery pack. The peak voltage coming out of the wall socket was about 170 volts so I figured it should work without a transformer. I would use a heavy off-board charger for charging at home with a higher charge rate.
Note: After intitial testing, I ended up adding a 12 volt boost transformer controlled by a standard light dimmer. This gave me some control over the charge rate and allowed me to charge at a higher rate.
The case is a thin aluminum box 10"x6"x3.75", with a removable cover.
The battery charger contains a 12 hour mechanical timer, GFI protection, 15 amp AC circuit breaker, 15 amp DC fuse, charger interlock relay, DC ammeter, pilot light, bridge rectifier, and a circuit to manage the individual batteries. There is a 25 amp, 12 position rotary switch (top left portion inside case) to check each battery. The rotary switch also sets which battery is the auxiliary battery. The whole charger assembly weighs only 4 pounds.
The left meter is the charging amps. The meter on the right is a 0-15 volt meter to check the condition of each battery in the pack.
The AC power input is shown on the bottom of the side view. The rotary switch knob is seen in the upper left while the 12 volt DC charger input is in the upper right. The 12 volt input lets you charge each battery individually with a single 12 volt charger or hook up a digital voltmeter to get an accurate check on each battery. The wires coming out of the back (on the right) go to the bridge rectifier, which is mounted on the aluminum controller plate.
The instruments are all by Westberg and could be placed as needed since the dash had never been drilled for anything.
The instrumentation includes 80-180V for battery pack, 0-150 volts for motor, 0-500 battery amps, 0-8000 rpm tachometer, and I am still trying to come up with a speedometer that will work. There are indicator lights for right/left turn, high beam, power, motor overheat, and one more to be determined.
I planned on mounting 12 batteries. I originally planned to use golf car batteries. The change from 72 to 144 volts meant that I would have to find a 12 volt battery that had a similar form factor to the Trojan T105. The batteries are going to run down each side of the car. I decided on using group 24 deep cycle batteries (trolling batteries). It has less capacity than a T105 but a little more than an Optima. Group 27 batteries would have been my first choice except that they are about 2 inches longer and would have stuck out too far.
The above image shows several battery types. The length and width vary only +/- about 1/8" between them. I designed for the tallest battery, the Trojan T145 which is not shown.
I designed the battery racks so that I could try other batteries later if needed. The trays will accommodate T105, T125, T145, T875, group 24, and Optima. I could assemble a pack between 72 and 144 volts using different types of batteries. Optimas are lighter and handle higher currents better. Flooded batteries are more forgiving. I built the charger myself, so testing it on flooded batteries is safer. I may also want to create a hybrid with a removable APU that replaces the rear seat. I would rather experiment with the cheaper flooded batteries until I work out more details.
The above image shows the cut steel for one of the two battery racks before welding. The steel is 2"x2"x3/16" hot rolled angle. The material weighs about 34 lbs. for each battery rack.
The above image shows the two battery racks after welding. I tried both gas and MIG first. The gas worked but took a long time to heat the thick material. The available MIG welder only went to 140 amps and penetration seemed insufficient. I ended up using a 230-amp Craftsmen stick welder that has been in our family since I was a teenager. The stick welder does not make pretty welds but it is fast and penetrates thick material easily. I ground down a few of the welds but most looked good enough to leave in their natural state.
I mounted each rack with five 3/8" bolts along the bottom and two 1/2" bolts extending through the body into the roll cage. The result is a very stiff chassis, roll cage, and racks. I loaded up the heaviest set of batteries I had (over 70 lbs. each), stood on them and bounced up and down. There was very little flexing. The 50 lb. batteries that I intend to use in the car should be fine on the road.
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