I have a 150cc 2 Seater gas gocart that I used for about 2 years. The starter motor stripped a gear 3 months ago and I decided to convert it to Electric Power rather than fix the gas engine.
Controller - $300
Motor - From old golfcart ($600 in store)
Wire - $20
Misc nuts/bolts - Already had them ($30 in store)
Contactor - $25
Diode and Resistor - $10
Sprocket - $35
Aluminum Plate and Bar - Already had in my garage.
Misc stuff that I had - $10-50
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Step 1: Motor
The label is worn off the motor casing but as far as I can tell its specs are as follows:
Type: Series Wound DC Motor
Max Current: 300A
Cont. Current: 100A
Max HP: 15
Cont. HP: 5
It was pretty rusted up and the pulley that was on it was a pain to remove. I took the motor apart and cleaned the dirt out of the coils, brushes and also greased the bearings.
Step 2: Motor Mount and Sprocket
Mounting the motor was mostly easy, there were a few hiccups on the way. The biggest one was that the motor has a tapered shaft and finding a sprocket that would fit was impossible.
I ended up buying a standard 1/2" 9 tooth sprocket and machining the inside out on a lathe, to a taper that would fit on the motor shaft.
The mounting plate consists of a 1/4" aluminum plate bolted to the frame, with a 2x1 piece of aluminum bolted to the back of the plate like a clamp to prevent the plate from flexing under the torque of the motor (300A makes an amazing amount of torque on a Series Wound motor).
If your wondering what the 2x4 piece of wood is for, I found out that the steel motor mount that was welded to the motor was not strong enough as the motor is designed for the plate to be bolted to the front with the shaft going through the plate. I didn't realize this until i took it out for a test run and it flexed so much that the chain would slip over the sprocket.
Step 3: Electronics
I used an Alltrax Series Wound Brushed DC Motor Controller (about $300) specs are:
Max Current: 300A
Cont. Current: 100A
Max Voltage: 50V
Min Voltage: 20V
Throttle Type: 0-5k
The power system uses 4 Gauge wire. They will get a little warm to the touch after doing donuts for awhile.
The contactor was left over from another project, this one is overkill and you really only need about a 150A contactor. but make sure that the coil rating is the same or a little higher than your system voltage or it can melt. (500A/48V)
The controller contains capacitors to smooth out the power flow. If the controller has no voltage on it and you apply power quickly it can destroy the controller. The Precharge Resistor keeps the capacitors charged even when the key is off. (20ohm/25watt)
When the contactor turns off, the coils create a huge burst of high voltage. The reverse protection diode stops this voltage from getting to the controller and damaging it. (600V/5A)
Step 4: Battery Pack
The current battery pack I am using is a Lithium Phosphate 42V/33AH system.
Later on I am going to switch to a 48V/110AH lead acid battery pack for more range and better reliability.
Capacity (WH): 1.3KWH
Capacity (AH): 32AH
Max Current: 800A
Cont. Current: 400A
It has a charger (120V ac) that will give a full charge in 6 hours.
The pack has a control board in it to protect from over charging/discharging and overcurrent. It also keeps the cells balanced which is crucial for a Lithium battery pack.
Step 5: Testing/Performance
I have tested everything from current consumption to 0-20 mph times
Top Speed: 22MPH
0-20 Time: 5.6 Seconds
Current @ 10MPH: 40A
Current @ 20MPH: 120A
Steepest hill here is about a 50 degree incline, it will climb at 15MPH at full throttle (about 270A)
Anything missing or that you want to know? Please let me know! by commenting me, PM me or emailing me at wolfcry0 at gmail . com
You can also talk to me on AIM @ wolfcryo if you have any questions.