Instructables
loading
loading
Picture of How to build a 72Volt electric motorcycle
FOR SALE  -  http://www.ben.cbccinc.com/BEM/forsale.htm

No gas, no oil and almost silent. 72 Volts, 70mph of pure fun. This is how I built an electric motorcycle.
 
Remove these adsRemove these ads by Signing Up

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.
1-40 of 569Next »
MechEngineerMike made it!27 days ago

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: http://www.instructables.com/id/Engineer-Your-Own-...

electric motorcycle.JPG
wraithsqaud6 years ago
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

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.

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.
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.
Thanks. That makes it make a lot more sense now.  I was not thinking about the inefficiency of the converter
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)  wraithsqaud6 years ago
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 Stryker6 years ago
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.
abhinavp548 months ago

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

Stryker (author)  abhinavp548 months ago

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

sraju310 months ago

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

sirscotty747 years ago
Glad I came across this site. There really is hope. How much does the motor weigh?
Stryker (author)  sirscotty747 years ago
72V Advanced DC AC4-4002 10”x 6.7” 47 Lbs from thunderstruck-ev.com
tcase Stryker7 years ago
Just out of curiosity, have you ever thought about a good generator, like off of a car or something?
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.
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.
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.
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........
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 tcase1 year ago

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 tcase5 years ago
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 Nyxius3 years ago
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 swander3 years ago
Why add an additional part? The motor can be used as a generator if regenerative braking is desired.
swander J-Ri3 years ago
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 swander3 years ago
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 J-Ri3 years ago
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 swander3 years ago
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 J-Ri3 years ago
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.
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.
 I think you refer to Hydroelectric power :D
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.
 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
Could you repost a link for the motor? I can't seem to find it.
Great job everything looks good. Is bike still 4 sale
Today is 11/01/2013.
Stryker (author)  jesus prado1 year ago
Yes it is. I upgraded to Lithium batteries but haven't ridden it in a while.
Diozark1 year ago
How Did You Connect The DC Motor Shaft to The Drive Sprocket ?
Stryker (author)  Diozark1 year ago
The sprocket has a set screw and the motor shaft has a flat spot to screw onto.
Hai how is your motorcycle working now. ?
Would you like to share some knowledge of yours experiences
Stryker (author) 1 year ago
I'm sorry I don't know.
1-40 of 569Next »