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How to build a 72Volt electric motorcycle

Step 2Components and tools

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 fromthunderstruck-ev.com.

Batteries: I went with 6 Yellow Top Optima batteries from remybattery.com 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 cloudelectric.com

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

Tools
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.

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40 comments
Aug 11, 2011. 9:11 AMeraj1 says:
hello sir,
Is there any possible of regenerating in E-bike.
Oct 20, 2010. 3:57 AMstingrayz says:
Why doesn't any one use the transmission from the original gas motor? Electric motors have higher torque. With gears it seams a person would get more distance from a charge. Using a touring type frame like from a Harley, the extra batteries could be in the saddle bags. This would put more weight on the power wheel for the wheelies. Lol
Aug 17, 2010. 8:17 AMeddieserrano27 says:
Great information...thanks.... questions? Should I care on how much amps the batteries have? Or the controller will take care of the amps completely? Should focus on how much volt the batteries can produces only?
May 5, 2008. 7:00 AMsirscotty74 says:
Glad I came across this site. There really is hope. How much does the motor weigh?
Jun 7, 2008. 8:51 PMtcase says:
Just out of curiosity, have you ever thought about a good generator, like off of a car or something?
Jun 24, 2008. 11:39 PMGrey_Wolfe says:
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.
Jun 25, 2008. 4:27 AMtcase says:
Thanks, thats very interesting, My father in law brought up a diesel engine alternator, or simply deal with gasoline...lol... 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.
Jul 15, 2008. 11:44 PMGrey_Wolfe says:
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.
Nov 1, 2009. 12:39 PMMrRodrigez says:
 I think you refer to Hydroelectric power :D
Jan 21, 2010. 11:14 PMGrey_Wolfe says:
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.
Jan 31, 2010. 8:51 PMMrRodrigez says:
 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
Apr 14, 2009. 7:21 PMvernonstien says:
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........
Apr 15, 2009. 4:47 AMtcase says:
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..
Jan 21, 2010. 11:19 PMGrey_Wolfe says:
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.
Jul 17, 2009. 9:08 AMNyxius says:
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.
Feb 16, 2012. 6:16 PMswander says:
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.
Feb 20, 2012. 11:03 PMJ-Ri says:
Why add an additional part? The motor can be used as a generator if regenerative braking is desired.
Feb 21, 2012. 7:17 AMswander says:
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.
Feb 22, 2012. 1:39 AMJ-Ri says:
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.
Feb 22, 2012. 8:55 AMswander says:
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.
Feb 22, 2012. 10:38 PMJ-Ri says:
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).
Mar 4, 2012. 7:49 PMNyxius says:
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.
Mar 6, 2009. 12:54 PMmr.sparkle says:
im trying to put together a drag bike over here in england instead of my gsxr1340 nos bike.range is not important any ideas on dc motors controllers ect hoping to run around eight sec i will build my own frame so motor /battery size not important thanks
Jan 24, 2009. 8:54 PMlogoris says:
is the dc-dc step down actually needed, and what is it actually used for?
Jan 29, 2009. 11:26 AMlogoris says:
o ok kool
Jan 23, 2009. 1:42 PMprabbit22m says:
Great job on the build. Brushless motors are really developing these days. They are basically AC motors but the Remote Control industry is making speed controlers that use DC and pulse it around the coils in the motor can to produce an AC type atmospere. These motors are very efficient and much more powerful. Of course they're expensive but some day they'll be cheaper and your bike with everything the same except the motor and controller will be a lot faster and have double the range.
Jan 17, 2009. 6:50 AMspmehta says:
Sir Its good, But dont drift creative forum into un necessary discussion like noise of MB Siddharth
Nov 9, 2008. 3:26 AMkurt168146 says:
Hello, I have been researching how to convert my bike, and have found that there are a few companies out there already selling kits, and out-the-box cycles but with 48 volts for power, but their range is almost double of what yours is. I saw your sample about volts vs.. ah and realize there is a trade off, but I am curious to know why you can't get both. Are there no Batteries available to produce a good 30 miles a charge and still get you up to 70 mph. for the highway? Thanks
Apr 10, 2008. 8:40 AMjongscx says:
you should re mount the muffler just to confuse people...
Apr 10, 2008. 10:05 PMSoakedinVancouver says:
Eh! A nice spot to hide the foldable solar panel!
May 1, 2008. 8:31 PMphreakincool says:
That's a really good idea! Noted!
Apr 10, 2008. 2:56 PMkishida says:
Maybe a fake muffler converted into a tool/misc storage might be useful?
May 3, 2008. 6:04 AMboxa888 says:
stryker, i read that a ac motor would give you more efficient energy transfer from your batteries because ac generates half the heat and waste of a dc motor, maybe upgrade that somehow and it could give you more milage. anyways awesome video, i was planning on doing the same thing but i need to get some money!! lol. awesome job, and very nice clean arrangement. yea you can buy like those mini solar panels from radio shack, maybe stick a few of those on there. awesommmmeeee!!!
Apr 10, 2008. 2:37 PMpfeng says:
That actually is a very good addition! One reason that motorcycles have loud exhaust (besides the macho factor, of course) is so car drivers are more likely to hear them, notice them, and hopefully LESS likely to crash into them. For 3 miles on back roads, I wouldn't worry :-) but if you wanted to go on major roads or highways, a noisy bike is probably safer.
Nov 11, 2010. 7:11 PMBGreenHVAC says:
You are exactly right. Nothing replaces the skill of a good motorcycle rider though. You would have to exceed the noise ordinance for most idiots to know you are there. I had a loud bike, but I almost got pinned between a Dually truck and a rock retainind wall. Even though my bike was loud, the idiot was talking on the phone, eating, jacking with the radio, and who knows what else. He just kept moving into my lane. I gus gave it full-throttle and sped to a safer position. Even though I flew past the dually, I don't think he ever knew I was there.
Loud pipes are a great lifesaving safety device. Also, I loved reving my engine and dround out the crappy noise that passes as music. I'd probably still laugh at the guy for making an imitation Harley noise. Most Harley owners would be offended. Play another engine....Perhaps the sound the rice-racer cars with the oversized exhaust (it kinda sounds like the muffler broke off....lol
Apr 12, 2008. 3:00 PMpfeng says:
@Stryker -- I'm sorry for turning the comments into a dispute over noisy bikes, I really didn't mean to!!!

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Author:Stryker