Cabling it up!

Wiring up the power system of the motorcycle is fairly straight-forward. It just requires using thick power cables that are connected with nuts on the motor and batteries, and nuts and bolts on the motor controller.

Cable Type
You will want to use what’s known as welding cable. Welding cable has many fine strands of copper cable inside. It’s designed to carry high current, but it is also very flexible, making it easy to work with. Other types of copper cable are very stiff, may not have the right type of insulation, and aren’t as easy to crimp to. Welding cable is available at welding suppliers, good full-service hardware stores, and some building supply stores.

Cable Thickness
The thicker the cable, the more current a cable can pass through it without heating up. Cable is commonly rated by American Wire Gauge. That measurement is a number wherein the higher the number, the skinnier the wire, and the lower the number, the THICKER the wire. Typical household electric wiring for 15 amps might be 14 ga, but electric vehicle cabling might need to be able to handle hundreds of amps. The motorcycle uses 4 gauge cable. It’s thick enough to carry the required current, but still be affordable. Thick cable can get pricey fast. (My electric car project uses recycled 2/0 cable!)

Get crimp-on power lugs that match the size of the cable you are using. They are available at the same place you got the welding cable from. 4 gauge is common enough to find locally. Make sure that the bolt hole in the lug is the right size to match up with the power connectors on the motor, the controller, and the batteries. If the various connectors are different sizes, get the appropriate number of lugs required so that you have enough lugs to fit all system components correctly.

You will need a mechanical crimper designed specifically for these heavy lugs. They usually come in two styles – “bolt-cutter”, and hydraulic.
The ones that look like large bolt cutters (long handles, small, jaw, almost always painted red for some reason….) work well and are fast and easy. They can be a bit pricey to purchase. They can sometimes be rented from full-service hardware stores. I borrowed one from a friend.
Hydraulic crimpers are typically hand-held with a small cylinder like a mini bottle jack. You pump the handle repeatedly to make hydraulic fluid crush the lug onto the cable. They have interchangeble jaw inserts for various diameter cables. The can be purchased fairly affordable at import tool stores like Harbor Freight.

Making Cables
To make power cables for the cycle, you need to know how long each cable is. Measure the distance between the two components using a flexible table measure or a piece of string (it’s almost NEVER a straight line between anything) You might want to account for having cables follow the shape of the frame or all be on the same side. In general keep cables as short as possible.

Cut the cable to length. Thick power cable usually can’t be cut with a small wire cutters. A bolt cutter will work fine, but the best tool I have used is a Sears Robo-Cutter. Any other type of large, sheering cutter will work fine.

On the end of the cable, slide on a piece of shrink tube, large enough diameter to go around the lug, and about an inch or so long. Then, cut back the insulation of the cable so that the lug can fully slide on, without having any left over bare wire. I used a utility knife to trim back the insulation, but if you plan to do lots of this in the future, you can buy a special wire stripper designed for heavy cable.

Crimp the lug on with the crimper of your choice. On some styles of hydraulic crimpers, they won’t release until you have FULLY crimped the lug. On “bolt-cutter” style crimpers, certain sizes require you to crimp twice.

Slide the heat shrink tube forward to cover the crimped part of the lug and the beginning of the cable insulation. Hit it with a heat gun or hair dryer set to hot so that it shrinks into place.

Physically connecting the cables
Connect all the cables, following the diagram provided in the motor controller manual. All four batteries in series – one to the next to the next to the next. Batteries to the controller. Controller to motor.
Without the main power turned on, the only concern electrically is that the batteries themselves always have power and that anything attached to them can carry current. Do not touch any power cables to the frame of the cycle, as that is the easiest accidental short-circuit. (Wear safety glasses whenever working with batteries and power connections. I also highly recommend wrapping the handles of wrenches that you use on the project with electrical tape, heat-shrink tubing, or other non-conductive material.)

Once the cycle is cabled up, you only have to check things over and test it all out before you can go for a ride!

{ 5 comments… read them below or add one }

1 Ray Hebert September 30, 2012 at 10:05 am

Thanks for the good advice on wiring up the batteries, and using heat shrink to help avoid shorting things out!
I have a Honda 750 Shadow shaft drive conversion that I’m working on. The rolling frame electrics are fully operational.(all lights, and horn.) Here is what I’m using on this build:
ME0913 PMAC motor, Golden Motor 72volt, 500 amp controller w/regen, Cycle analyst meter, 6- 120 amp/hr deep cycle batteries from Costco, #2 welding cable, and 72 v 10 amp battery charger(for now, ’till i invest in a 20 amp charger later.)
The motor will be hooked up direct drive through the origional universal joint (modified to work on the motor shaft.) The ratio is 3.3 : 1 as is. 4 batteries are going in the frame, 2 will be mounted in “saddle bag” style.
I’ll be getting the controller on Wed. 3/12. I’m ancious to see how this set-up performs!
Best Regards,

2 Ben N October 1, 2012 at 10:08 am

Hi Ray,

Sounds like a great project!

On the list of “things to think about”…. Flooded batteries will take up more space in a motorcycle, because you have to allow room to access the tops of the batteries for watering and maintenance. It’s kinda tough to stack them, the way you can with SLAs or AGM batteries. I dumped my cycle once so far. It was completely sideways on the road. It wasn’t a problem at all with the AGM batteries, but might make a real mess with flooded!

I have a friend with a shaft-drive cycle project that never really got finished. We found out that direct-drive at low voltage to a drive shaft didn’t work very well. He didn’t have a very good motor either though – just a low-power no-name forklift motor. At 72V, and with a good motor, it might work great! You just have to keep your eye on the amps, and the higher the voltage, the lower the amps.

Some people who have done drive-shaft conversions put a “jack-shaft” in there to add a little gearing between the motor and the drive shaft.

Sounds like a great project and I think we would all love to hear more about it as you go!

3 donald hoppe June 21, 2015 at 5:09 pm

yo love your vectrix project. try trimming down the windowshield its pretty tall. I wonder about leaving an airgap at the bottom of windowsheild to decrease the airpressure on the backside,. an wax the bike. also the afore mentioned bearings. if I find one what should I pay? how much to help me change batterys?
Donald hoppe
monark meadows apt.119
n Mankato Minnesota 56003
713 829 5124

4 donald hoppe August 28, 2015 at 4:00 pm

i watched all your dvds on the vectric conv. wow ok I have 3 vx-3 I have a stroke. would you be interested in a vectrix vx-3 -battery to help me get one going? ps im building a li-on batt. for a mobility scooter 24 volt 70 amp yo see ya. pss luck on your trip that’s beautiful country in the upper pu.

5 donald hoppe August 28, 2015 at 4:03 pm

vx-3 should have said minus battery.

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