1976 Fiat Spider 124 EV Conversion

Well it moves with the small motor and three old batteries. Got about 10 mph on 25 amps at 36 volts in first. Overheated the small motor in second. Small motor only a 5" dia 24V winch motor. Its a glorified golf cart with a very kluged up system. Now to take into consideration all the forum suggestions and do the real engineering and build. Got to get a bigger motor, better coupling between motor and transmission, do away with the throttle and clutch pedals and mount the electric pedal. Figure out the battery type and how they will be mounted. Then paint and put the normal car electrical back in. This is a real DIY project, only $2400 in so far including the donor car. Now the big bucks.

Bought a ME1003 DC PM motor from Electricmotorsport. 12-72 volts, 15 hp continuous, 26 hp peak. Measured stall torque and got a slope of 0.8 ft lbs /amp. Based on the weight of the Spider the motor should give the Spider good performance. Surprisingly, under no load the motor start rotating at only.5 amp. The advantage of a PM motor, no field to excite. Initially using the Lovejoy coupling. Ridged coupling is having the female spline welded on. Alignment of the inline and radial dimensions accomplished with the transmission vertical. When aligned the coupling moves up and down on the trans/motor shaft with very little resistance. Than bolts torqued down and freedom of coupling checked again. With transmission horizontal, no noise or vibration, no load at 1000 rpm. Initially will use a 36v 275 amp controller I have with three 12v deep cycle batteries. Just want to get the Spider moving so I can start the EV registration process. Not worried about range yet. Initial rough estimate is that I will get 1 mile on about 800 watt hour, level 60 mph, worst case. This is based on static rolling resistance and expected wind resistance. Expect dynamic conditions to be much better. So far only measuring controller current and voltage, amp and watt hours used, and motor RPM and temperature. Working on speed, vehicle tilt angel and acceleration. Need to investigate possibility of regeneration from the DC PM motor. Into the project $3400.

Larrybia said:

Are you referring to HP or torque? Check out the 1976 Fiat torque and HP curves. Not so good at low end for the torque or high end with the HP.

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The point of a transmission is to allow the engine (or electric motor) to turn at the desired speed. After the first second or so of acceleration, suitable shifting will always have the Spider's engine able to put far more power than the peak power of that electric motor.

Yes, engine torque is low at low speed - although available torque output of the 1756 cc Fiat engine is higher than the ME1003's continuous maximum of 315 inch-pounds (26 lb-ft) at any engine speed from idle to redline - but for extreme performance the simple solution is just slipping the clutch. The torque output from the clutch is the same as the input (a clutch doesn't multiply torque but it also doesn't lose any), but it allows the engine to turn fast enough to produce more torque; ideally the driver slips the clutch just enough to allow the engine to run at its torque peak. After a second or so of slipping the car is moving fast enough that slipping isn't needed any more. The lower the performance expectation, the less slipping is used... down to a small fraction of a second in normal driving. With peak torque available down to zero speed, an electric motor doesn't need a clutch at all.

Larrybia said:

Torque is acceleration, HP is speed.

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While that is often stated, it's nonsense. Torque at the engine or motor doesn't matter; torque at the wheels is what matters but that torque multiplied by wheel speed is power.

If you use AC induction/asynchronous motor, you can consider using our controller.

Completed some testing with the ME1003 motor and a 36 v battery pack. Three Group 24 lead acid deep cycle batteries from my RV. Very satisfied with the performance considering the battery pack. Drove 3 miles with max speed of 22 mph and also doing acceleration tests. Used only 30 % of the battery pack. On starting in 2nd gear got max acceleration of 3 M/Sec^2 with two large guys in the car. Performance matched prediction pretty well. For reasonable driving stability added an additional 150 lbs ballast in the front to get the correct tie toe in. Weight distribution is critical when modifying from ICE to EV. Either redesign the suspension or load the car as if it had an ICE. Getting the lower weight batteries and paying the higher price may not always be the best solution. Consideration of driving conditions (Stop and Go and Hilly Terrain), type of battery care you will need to do and cost to redesign suspension needs to be considered. I am not trying to build a performance car but just one that is surface street worthy and at the lowest price possible. Next phase is to to install a 72 volt battery pack and a higher voltage/current controller. Plan to put three more batteries in the front and do away with the ballast. Need bigger cables because they got warm but the motor saw no change in temperature. However, its cold here in Colorado. Also if I want more range can add batteries in the trunk. Getting 6 new batteries and the controller will add about $1000 to the already $3500 I have into the project so far. That includes $1500 for the donor car. Then I got to paint the car, get a new windscreen, redo the normal electrics and clean up the interior and get it registered.