Introduction: How to Build a 72Volt Electric Motorcycle

Picture of How to Build a 72Volt Electric Motorcycle

No gas, no oil and almost silent. 72 Volts, 70mph of pure fun. This is how I built an electric motorcycle.

Step 1: Why and How

Picture of Why and How

I only work 3 miles from home but with gas prices getting out of control, I thought it would be great to have an electric vehicle. I've always wanted a motorcycle and decided that making an electric motorcycle would be a good EV project, keeping costs down, and be fun to ride.

This project took about 3 months of research and development (not counting waiting for parts to come in or help from a friend with the welding). All in all, it cost about $3000 to buy and build. This may take a long time to pay off in gas savings, but if you add the fun of building and all of the environmental benefits, it was well worth the effort. With a top speed of over 70 mph and 10 miles per charge, this vehicle is perfect for me. The following instructable will not give you exact step by step instructions, but if you have some mechanical skills and welding ability you should be okay. A little knowledge of motorcycle maintenance wouldn't hurt, too. However, I just read the user's manual and learned as I went.

Step 2: Components and Tools

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Every motorbike is different but the basic components can be the same. Below is a list of the parts I used and where I got them, but you will have to do some research to figure out what fits your bike and requirements. Check out the photos at the bottom to see what I bought and the EVAlbum for other electric vehicle projects.

Frame: I looked at many different bike styles and decided on a 1984 Honda Interceptor for a few reasons:
1) I like the style of bike, not a total crotch rocket but not a hog either, with room for batteries inside the frame.
2) The seller on Ebay was close to my house. And the bike didn't run, so it only cost $600. If you have an old bike or someone will donate one then that's great--but for the rest of us, try the local paper, junk yards, Craig's List or ebay motors.

Motor: After reading other EV bike specs (and knowing that I wanted to go faster than a moped), I chose a 72V Advanced DC motor, because it's weight and dimensions where good for my frame. I ordered it online

Batteries: I went with 6 Yellow Top Optima batteries from because they are sealed and have received great reviews. After making cardboard mock ups of the D23 model I realized that there was no way six full sized batteries would fit and still look good. I ended up getting the D51 model. Half the size and weight but also half the storage.

Controller: You have to match your controller to your voltage but the amperage is up to your budget. More amps = more power and more cost. It seems that there are only two real choices: Alltrax or Curtis. You'll have to decide for yourself, but I went with the 72V 450Amp Alltrax from cloudelectric. Don't waste your time trying to build a potimeter on an old throttle--just buy a pre-made one and be done with it. I got the Magura 0-5K Twist grip throttle from

Charger: You have to match your charger with your voltage but the speed of charge in Amps is also up to your budget. I went with a Zivan NG1 from EVAMERICA I have recently switched to six individual 3amp Soneil chargers to help balance the batteries.

DC/DC Converter: It's safest to run with a DC/DC converter and an extra 12V battery backup but motorcycles have limited space so I am only using the converter. I purchased a Sevcon 72V Input 13.5V output from evparts and it has working perfectly.

Fuses: You'll want to get a fuse that matches your setup. I bought model ANN 400 w/ holder from EVAMERICA.

Contactor: This is a device that you hook up to your existing key ignition on 12Volts and it will close the loop so you get the full power to your controller. I bought an Albright SW-200 from EVAMERICA

Battery cable and connectors- I bought about 10 feet of 2 GA wire from WAL-MART and cut it to length. Using Lugs from cloudelectric I soldered and used heat shrink tubing on each end. I highly recommend battery terminal covers for safety.

Instruments I chose an E-meter(Link 10) w/ Prescaler add on for 72V use instead of a bunch of different meters. As an added feature I wired up the ignition switch to the neutral indicator to show me when the bike was on.

Other parts
Wire - 12GA different colors and heat shrink tubing (large and small sizes)
Electrical tape
Wire connectors
Wire wrap

Basic shop tools are required such as a socket set, screw drivers,wire stripper, etc. Additionally a volt meter, metal grinder and crimper are used in this project.

Step 3: The Build

Picture of The Build

Start by removing all of those nasty internal combustion engine parts. Remove the gas tank and using your grinder or other cutting tool to cut out the bottom. This makes room for extra batteries or components. (Make sure all gas is out before cutting) Reference your owners manual so that you don't cut any necessary wires, and try to sell some of the parts to help pay for this project.

Next, make cardboard mock ups of all of your batteries and electronic components to see how and where things are going to fit. Take a look at my pictures to see how I fit everything, believe me that taking the time to make accurate cardboard mock ups is well worth the effort.

Now for the hard part. You need a secure battery box and motor mount. I had a friend weld it up for me and he did a fantastic job. From the photos you can see that he first strung up the motor to allow for minor adjustment to be made before cutting the motor mount plate. After that was cut he made a nice chain and sprocket enclosure with a door and welded them onto the frame.

Next he fabricated the battery rack and gave each battery a swing arm closure to give a tight fit yet still allow me to get them out easily. Half inch foam padding spacers are between each battery to help cushion the stack--but believe me, they aren't going anywhere. The last thing
he did was weld in metal plates for mounting my electrical components.

After you get your motor mount and battery compartment all welded up, take some time to clean up the frame of your bike. I removed any rust spots and chipped paint that I could find. Then I used some metallic gray and black spray paint. This makes a world of difference and costs very little.

I made a fake gas cap and ran the power cord from the charger up the frame and out the top.

Now that you have all of the welding done and your frame looks great, let's install the electrical components and start wiring it up.

Step 4: Wiring

Picture of Wiring

If I tried to explain where to connect every single wire I would get writers cramp. View the wiring diagram that I put together and let me know if you have any questions. This diagram should be pretty accurate to how I built mine, but obviously you are responsible for your project.

Step 5: Last Few Things

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Double check all of your connections and tighten every bolt.

I wanted my bike to look as good as it rides, so I had all of the panels painted and custom graphics made up by worldsendimages.

Using a serial cable and laptop, tweak the speed controller program for your riding preferences.

Lastly, I got the bike inspected and insured. (Be prepared for the dealership mechanics to swarm and hit you with a bunch of questions and jokes about failing the emissions test).

I know these weren't step by step building instructions, but that's because of the complexity of this project and variables in component use. My intention was to give you the motivation to build your own by seeing how I did it and make it easier by supplying the parts list and a wiring diagram.

For more photo's and a build commentary visit my website at


logicnine (author)2016-12-21

I've finished an EV bike of my own, however, I cannot find a drive sprocket and no guide talks about what sprocket they used. I am running an eTek motor with a 7/8" output shaft and a 3/16" keyway on a 520 chain, likely a common setup... what sprocket did you use? Where did you get it? My project is sitting in the garage until I find one :(

Stryker (author)logicnine2017-01-17

Hi, Sorry but I don't know much about the gearing. I had a friend who works in a machine shop get the sprocket for me. It fit so we used it. I thought about changing tooth ratio for more range, but never got around to it. Try asking a few of the people that built bikes over at EVAlbum motorcycles section.

Nettoast made it! (author)2016-02-22

Took about 6 months over the winter of 2010 to make. Picked up the bike for $400 on Kijiji, blown engine and rusted tank. Bought most of the components from Cloud Electric in the U.S., lucky to have a source of used gel cell batteries (free) every four years from a UPS at work.

Motor is 72vDC with Kelly controller, hooked up the regen to the clutch microswitch so when I am going downhill I pull in the clutch lever to regen (and this also adds lots of drag, so saves the brakes).

14 tooth drive sprocket, 71 tooth at the rear gives me top speed of 70kM/hr and amazing acceleration off the line. I get about 35kM per charge (the batteries I get have been in use for four years in the UPS, so this is not bad for free batteries). Enough for the 10k round trip to work, and some running around on top of that.

On board charger, 125vAC cord comes up through the filler cap. Takes about four hours to fully charge, and a year's hydro runs about $7.00.

72v>12v converter runs all the lights and horn, converted all lights (including headlight) to LED.

Lot's of fun, and really gets attention at the bike shows!

Total props to Stryker for posting this and spurring me to build this!!

DanielT100 (author)Nettoast2016-05-06

wow it looks great.

UltraRaven (author)2016-05-03

I owned the '83 intercepter... Fastest track bike of 83... I miss it too... Hopefully you were able to sell parts from the bike to help not only yourself with funds, but someone who needed parts to get their bike going again... Great motor on those. Hope you had fun

TyL4 (author)2016-02-10

i really hope the parts from that interceptor went to a good home to give life to another. Very valuable and rare bikes...

JacobT11 (author)2015-08-04

Exactly what I've been looking for to get my own conversion off the ground. Thanks very much for taking the time to post

MechEngineerMike made it! (author)2015-06-07

Looks great! Good luck selling the bike, be careful not to set yourself up for a lawsuit! I decided to strip my own bike down and sell it peace meal for this very reason. If you're interested you can read about my project here:

wraithsqaud (author)2008-09-22

is there an advantage to wiring the batteries in series and converting the voltage for the bike systems down instead of wiring them in parallel and converting the voltage up for the motor

SA Phil (author)wraithsqaud2015-05-23

You would get killed on Booster inefficiency going from 12V to 72V.

With 72 volts you can use smaller wires since you wont be carrying as much current. All of your design concerns will be based on Ohms law, Voltage = Current* Resistance. Always best on a mobile system to use as high a voltage as possible where possible. A fighter uses 400 Volt motors for example.

Better off only converting back to 12 Volts to run lights and control things where necessary. Or alternatively use a smaller 12 volt battery that is not part of the 72 volt system.

DabeAltis (author)wraithsqaud2009-07-11

Wraithsquad, since nobody ever really answered your question, I'll put in my two cents. There is indeed a tremendous advantage. The power that is downconverted to 12 volts to power the control system, lights, etc., is a very small percentage of the total power of the batteries, and therefore a relatively small and inexpensive DC to DC converter will do the job. If you went the other direction the converter would have to be much larger and much more expensive. It would have to handle the lion's share of the load and battery power. This conversion is not 100% efficient, therefore the power lost in conversion would much higher. The current from the battery pack would be at least six times as high, therefore would require larger conductors and would be much more susceptible to resistance losses. I realize your question is almost a year old, but I am new to Instructables. Hope you get a chance to read this reply, and I hope it helps to answer your question.

knikol (author)DabeAltis2010-07-21

I think some of you may have missed one of the points regarding the voltage converter. Only the motor is operated directly from the 72-Volts through the controller. The voltage converter is only there to operate the 12-Volt lights, turn-signals and such. The author's approach is probably the best trade-off in efficiency vs. weight, as opposed to a separate 12-Volt battery for the accessories.

wraithsqaud (author)DabeAltis2010-03-13

Thanks. That makes it make a lot more sense now.  I was not thinking about the inefficiency of the converter

dillweed2 (author)wraithsqaud2008-10-10

The batteries are connected in series, (pos to neg) to increase the voltage. Voltage is electrical pressure, comparable to PSI in a hydraulic system. The higher the voltage, the better efficiency and performance of a product. That's why you saw cordless tools go from 3V to 7V to 14V and now 18Volts. Wiring in parallel ( pos to pos and neg to neg) is how you jump a car battery. Parallel increases the amperage or capacity of the system while keeping the voltage the same. Flashlight batteries are connected in series (a 5 cell would be 7 1/2 volts). That's why electrical companies transfer power in thousands of volts, less resistance is greater efficiency.

Stryker (author)wraithsqaud2008-09-22

I don't understand what you mean. But I'm no electrical engineer so I doubt I could answer it if I did understand.

msee (author)Stryker2008-09-25

Assume 12V deep cycle batteries.

Series Connection
6 x 12 = 72 V
72V x 100A = 7.2kW (or ~10 HP)

Designing a motor/controller combination to handle this voltage and current range is pretty easy and relatively inexpensive. There are MANY currently available.

Parallel Connection
1 x 12 = 12 V
12V X 600A = 7.2kW (or ~10 HP)

Although a DC-DC converter can be designed to convert 12V 600A to 72V 100A, it will add significant cost and weight, and will reduce efficiency of the overall system.

A motor could be designed to use 12V 600A, but it too would be less efficient because...

Resistive losses are a function of I*I*R, so as current increases resistive losses go up FAST. The lower you can keep the current, the better. That is one reason why AC power is transmitted over the grid at very high voltages and then stepped down locally.

abhinavp54 (author)2014-10-15

What power batteries and motor do I need to get in order to get at least 50 miles per charge

Stryker (author)abhinavp542014-10-16

I'm not sure, but I would say a lot......

sraju3 (author)2014-08-27

sir,i want to build a electric motor cycle which should have top speed of 50-60mph and it should have a mileage of 70-80 miles per charge would anyone can suggest me required motor,batteries and controller set ups

sirscotty74 (author)2008-05-05

Glad I came across this site. There really is hope. How much does the motor weigh?

Stryker (author)sirscotty742008-05-05

72V Advanced DC AC4-4002 10”x 6.7” 47 Lbs from

tcase (author)Stryker2008-06-07

Just out of curiosity, have you ever thought about a good generator, like off of a car or something?

Grey_Wolfe (author)tcase2008-06-24

Car alternators really aren't all that good. There are better options, though with something like this, one might like to go custom. Maybe use permanent magnets instead of coils, that also would aid in battery life. That's kinda intentional though, like the 18% fuel efficiency they have so you have to buy more gas and your engine wears out sooner.

tcase (author)Grey_Wolfe2008-06-25

Thanks, thats very interesting, My father in law brought up a diesel engine alternator, or simply deal with he's been a mechanic for years, sometimes an annoying one that likes throwing wrenches at customers who try to tell him how to do his job, but a good mechanic. He likes the idea of saving money for gasoline by other alternatives, solar power or if you have a creek on your property build a wheel like the old days, I forget what its called, but putting a generator on that to make electricity. anywhere you save money can help. then just dish out the money for gasoline at the pump. I kind of fancied the air compression engine actually, going to try that someday... still takes money though. take care and great Instructable.

Grey_Wolfe (author)tcase2008-07-15

I read something about a hydrolic compression engine once. Done by a University class (maybe University of AZ, not sure). It used a combustion engine, but instead of driving the car with it, they used it to build up hydro pressure, then use the pressure to drive the car. Could get up to speed reasonably, and stored breaking energy to allow smooth take off from stops. That would probably fit the same principle as your air compression idea, at least for design purposes. Got like 80 miles to the gallon. The wheel you spoke of is simply called a water wheel, though there might be another (more proper) term.

vernonstien (author)Grey_Wolfe2009-04-14

I think I saw an article in Machine Design magazine a while back about using hydraulic motors to drive wheels, one motor per wheel. it is possible to use a gas motor to drive hydraulic pumps to produce power, dump truck, garbage truck. bull dozer, ect. ect........

tcase (author)vernonstien2009-04-15

Thats cool, I think my biggest problem is having something that goes the distance for an electric... you get on a motorcycle today, and its like, you can refill anywhere, yea, you can plug your bike into plugs at grociery stores, but to me, according to one person, he plugs his car in at the light poles in parking lots.. like walmart. to me, thats still stealing, even though it is available... I want to find a way to build an electric motorcycle, ( Im a fan of the sportster models ) it still look good, and be constantly recharging while driving.. kind of like having an alternator from a big truck similiar to a dump truck or semi. Im not sure on how to put all that together considering I have nothing to use to start experimenting yet... I have to wait to buy a house before I can start tinkering, thanks for the last comment It sounds like it would come in handy... or at least experiment with.. My uncle works with a backhoe at work they have alot of parts just laying around I might be able to pick up for a few dollars for alot of their heavy machines... but I dont think I need to build a tank, even though it sounds like fun...thanks again..

lucek (author)tcase2014-04-06

You'd be talking about reactive breaking then. It'll help but I'm not shore if the extra weight will overcome the savings in energy. After all just because you slap an alternator on it doesn't mean it's making energy. It's taking energy from the battery to the motor to the bike to the breaks to the alternator and back to the battery with losses at every step.

Nyxius (author)tcase2009-07-17

Using your alternator to charge your batteries while you drive will only kill your batteries faster. alternators have maybe 50% eff. converting kinetic energy to electric. but the full load is being introduced to your electric motors. Thus you may be getting a couple watt charge out of it, but it will consume far more than that in the extra juice needed to power the motor.

swander (author)Nyxius2012-02-16

using an alternator while braking would regenerate otherwise wasted momentum. Make a switch into your brake lever that activates or "turns on" your alternator that would otherwise be free wheeling, making no power with minimal drag. When you turn it on, you can regulate the amount of "exciter" voltage and the amount of drag the alternator will be putting on the freewheeling wheel. more braking. more drag, like a jake brake in a truck. Wont use it all the time only when it is safe like on a downgrade or slowing for a light.

J-Ri (author)swander2012-02-20

Why add an additional part? The motor can be used as a generator if regenerative braking is desired.

swander (author)J-Ri2012-02-21

Because you can regulate an alternator easier than a generator. also alternators have better low RPM efficiency. Regulate with input voltage or variable ground, your choice.

J-Ri (author)swander2012-02-22

I do agree that it is easier to regulate an alternator, but only slightly. An N-channel MOSFET connected to ground would use the same PWM as an alternator's field terminal. Many alternators use a 12v (or 24v) field signal, and some provide the current for the field coil as well, either of those cases would require a transistor anyway.

Could you provide me a link to some documentation that says an alternator has better low RPM efficiency? My research in wind turbines suggested that at best, alternators and generators have the same efficiency at low speeds, and most seemed to agree that generators are better at low RPM.

A transistor controlled ground is one more part, and a much cheaper, easier, smaller and lighter one to install than an alternator. I suspect it would also be difficult to find an alternator that can output this kind of voltage. Many have a fixed regulator that won't allow excess voltage in the event that the computer controlled one malfunctions and full-fields, and even one without that protection probably isn't built to output this voltage and may fail prematurely. Even on a car where the alternator is typically driven at approximately 3-5 times faster than the crankshaft, the voltage will drop to below the desired charge voltage with only a few amps drawn at idle 500-1100 RPM (1500 to 5500 RPM at the alternator). So that alternator designed to output 12 or 24 volts would have to be geared up considerably, further adding weight and frictional losses from the gears. An additional load on the motor would require more power from the motor to spin it up to speed. Try spinning one by hand, the rotational mass alone would take considerable power to get moving, especially with the gearing required to spin it fast enough to make this high a voltage.

swander (author)J-Ri2012-02-22

simply going by what the car industry did back in 1965 when some went to alternators instead of generators for better low speed charging ability. Now stepping these up to 72 volts is out of my pay grade. efficiency between 50-62% is typical of an automotive alternator, they are cheaper, lighter and are more durable with low current slip ring brushed instead of full voltage DC brush design. 1200-1800 RPM is generally idle speed in a automotive alternator, and they are in almost unlimited supply in varying amperage output from small 30A tractor units to 240A modern car units. Cheap is good.

J-Ri (author)swander2012-02-22

The primary reason they switched is that alternators are smaller and lighter for the same output, but we already have a dc generator (the motor) on this bike. The rated amperage is only short term (but likely acceptable for use as a regenerative brake), for sustained output, they have a maximum of half their rated value. And the higher amperage ones are huge, a 180A alternator from an F-350 is larger than the motor used on this bike and weighs 20 pounds (a guess).

Nyxius (author)J-Ri2012-03-04

If you are insistent on regenerative braking (using the motor), may I suggest using a brush-less motor coupled with some super caps. Batteries don't like the sudden spikes in voltage that regenerative braking gives. You need a way to smooth that out over time, or your going to kill your batteries. Regenerative braking is essentially a collapsing magnetic field with an inductive coupler (rate of field collapse is motor dependent). Without something to buffer your batteries, your electrodes in the battery will start to breakdown (beyond what is normal) and will probably cause a breakdown in your electrolytic material as well. This generally results in electrolytic gassification. This is why liquid capacitors burst and this is the reason they say to not overcharge batteries.
Also, regenerative charging using a brushless will most likely require a weird bridge rectifier (3 phase+) with a negative feedback loop.

Grey_Wolfe (author)tcase2010-01-21

Nyx is pretty accurate, you can't receive a net gain in power while using the same type of energy to drive the vehicle.

You would need an external source of energy input into the system while driving.

It would be possible with large scale technology similar to the proximity charging devices we have recently developed for small electronics. But the cost to create such tech on a large enough scale to charge while on roadways is not feasible at this time.

MrRodrigez (author)Grey_Wolfe2009-11-01

 I think you refer to Hydroelectric power :D

Grey_Wolfe (author)MrRodrigez2010-01-21

No, it was driven by hydrolic pressure, not electric motors. I'll ask my dad if he remembers the University that did it and post more info.

Sorry about the late reply, been away from the site for awhile.

MrRodrigez (author)Grey_Wolfe2010-01-31

 Lol i meant when you said this: 

"The wheel you spoke of is simply called a water wheel, though there might be another (more proper) term.

but yeah, the type of engine you spoke of originally has actually been produced, and soon is supposed to be commercially made, although it's actually a pneumatic engine that refills it's tanks when plugged in. :D sounds pretty sweet to me

smccollough1 (author)2014-01-07

Could you repost a link for the motor? I can't seem to find it.

jesus prado (author)2013-12-01

Great job everything looks good. Is bike still 4 sale
Today is 11/01/2013.

Stryker (author)jesus prado2013-12-02

Yes it is. I upgraded to Lithium batteries but haven't ridden it in a while.

Diozark (author)2013-10-19

How Did You Connect The DC Motor Shaft to The Drive Sprocket ?

Stryker (author)Diozark2013-10-22

The sprocket has a set screw and the motor shaft has a flat spot to screw onto.

bkdhanushka (author)2013-09-01

Hai how is your motorcycle working now. ?
Would you like to share some knowledge of yours experiences

Stryker (author)2013-08-05

I'm sorry I don't know.

jehuty9800 (author)2013-08-05

what king of current is the motor drawing, running at? im doing my research before i convert my old 82 honda nighthawk into an EMotorcycle. 72 volts seems like its the best option, i just need to know what the amperage is that the motor is drawing.

nehmo (author)2013-07-21

Lead-acid? The main thing I learned from my e-bike experience, which is ongoing, is shun lead-acid. They are inferior to the lithium chemistries in specific energy, cycle life, and C-rate.

kelevra88 (author)2013-02-18

How long could you expect to get from these batteries ,Mileage and/or lifespan?

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