Introduction: Build Your Own ELECTRIC MOTORCYCLE
The finished project is a 1981 Kawasaki KZ440, converted to electric. It is powered by four Optima Yellow Top sealed (AGM) lead-acid batteries, that drive a Briggs & Stratton Etek electric motor. The speed of the motor is controlled by an Alltrax brand "AXE" programmable controller that can run at up to 48 volts and 300 amps. Contrary to popular belief, and electric motorcycle is NOT silent, but is CONSIDERABLY quieter than a typical gas cycle.
The cycle is GEARED to 45 mph, has fairly good acceleration, no clutch or transmission. There's no oil to change, to mufflers to rust off, no air filter, no carbs to tweak, and no gasoline. I designed it for primarily city riding. The top speed and acceleration could be easily changed by swapping out a $20 stock sprocket.
The cycle recharges from the wall, through a renewable energy program, and if there is a blackout, I can actually run my house off my electric motorcycle! In the future, I hope to expand my system to include charging the cycle with photovoltaic solar panels. Real-world range per charge is 23-32 miles, and charging takes less than 10 hours for a full charge. ( A different charger could charge them even faster - see details on the Batteries PDF)
In this Instructable, I'll walk you through the work required with the motor, batteries, controller, and mounting all components, including showing you some low-tech paper and cardboard "CAD" tricks.
But what do you want? You might not even know yet. I always encourage people to take a look at the EV Album. It's an on-line listing of mostly home-converted electric vehicles. Each listing shows the make and model of the vehicle, the cost to convert, the speed and range, and other specifics of each project. You can also search by type of vehicle or brand name.
For example, if you go to http://www.evalbum.com/type/MTCY , you'll see a wide variety of electric motorcycles. Different brand names, lithium and lead-acid battery types, and a wide range of costs of conversion. Likewise, if you want to see Scooters, Mopeds, and Minibikes, you can visit http://www.evalbum.com/type/SCMM
Give some thought to what cycle you would like to convert. Do you like sport bikes? Great! They have a lightweight and strong aluminum frame! Do you like standard? Great! There's lots of those out there and you can show off the motor and batteries. Hang out at biker events with your unique ride!
If you aren't sure what to expect in terms of range per charge and top speed, don't worry, online calculators can help you out.
EV RANGE/SPEED CALCULATOR
Power Use at Speed Calculator
and of course, a
GEAR RATIO CALCULATOR
For more on my electric motorcycle, electric car, and other projects, swing by my blog at http://300mpg.org/
If you are interested in building your own electric motorcycle, but want even more information, more details, and hands-on style instruction, check out the INSTRUCTIONAL VIDEO DVD that I created to teach how ANYONE can Build Your Own Electric Motorcycle!
As of January 2018, I've now posted the Instructional DVD, the entire 2 hours and 40 minutes of it, FOR FREE on YouTube. The DVD is broken down into shorter sections and available as a playlist.
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Safety
It may be cliche, but every shop class, repair book, and seminar starts off talking about safety.
The reason why is because IT'S IMPORTANT! Any type of work always has some sort of risk to it. Minimize that risk, and protect yourself by thinking ahead and using proper safety equipment.
I'll hit a few of the basics here, as well as a few you may not have thought of that are particular to this project.
Personal Protective Equipment
Wear your safety glasses, work gloves, and hearing protection. If you already wear eyeglasses, the larger "boxy" type safety glasses work well over your eyeglasses. Otherwise, add side protectors to your existing glasses. If you don't wear eye-glasses, I like the the slimmer style that fit tight to the face. This is the same type some motorcycle riders wear out on the road. Heck, get yourself a nice pair, and they are multipurpose!
Wearing work-gloves will save your hands a lot of cuts and scrapes. Thick leather gloves are durable, but clumsy. Mechanics gloves give you much more dexterity. I prefer these, as I can leave the gloves on while using any type of tool. If you have to take gloves on and off to use a particular tool, it doesn't take long to give up on wearing gloves. Wear welding gloves when welding. Latex or other rubber gloves are sometimes handy for working with fluids or while painting.
Wear hearing protection. During any drilling, cutting, or grinding, you should be wearing hearing protection. Soft ear plugs are cheap and disposable, and pretty comfortable. I like the big "ear-muffs" because they are easier to take on and off than soft plugs are to take in and out. I like having "normal" hearing while I am not cutting and grinding.
Remove jewelry, or at least cover it up. Besides getting caught on a moving part, most jewelry is also extremely electrically conductive. Remove rings, wrist-watches, necklaces, wallet chains, and that big key chain hanging on your belt loop. Don't wear big conductive belt buckles that can also scratch paint-jobs. If you can't or won't remove a piece of jewelry (wedding rings, etc.), cover it up. Wearing work gloves will cover a ring, and a necklace can be tucked inside your shirt.
Clothing. I'm sure you've worked on enough projects that you know what appropriate clothing is. Typically, you want long shirt sleeves and long pants. Don't cuff your pants. Metal shavings, dirt, and possibly hot metal likes to get caught in there. Wear closed-toe shoes or boots, preferably leather, and safety toe if you have them. Natural fiber clothing is also preferable. In a bad situation synthetic fibers can melt (onto a person!) At least wear a cotton T-shirt under your fleece sweatshirt....
Now onto a few things that are more specific to this project.
Motocycles are powerful, heavy enough to hurt if they fall on you, have chains and sprockets, and run on electricity by the time we are done with it.
That brings up a few safety cautions of particular concern:
Pinch Points: Be really careful where the chain and sprockets come together! Always make sure you have the chain guard in place. Build a custom chain guard if the project requires it. I once got my finger pinched between the chain and back sprocket when I was adjusting the chain. YEOWCH! That was just with me turning the back wheel slightly by hand. I'd hate to imagine if the same thing happened with the motor running!
Electric Spark and Shock: Always keep covers on the battery terminals. Never work on the cycle with the power connected. Always have the real wheel off the ground when testing the vehicle. Keep conductive materials away from the batteries. 48 volts is right on the border of what is generally considered low-voltage or not. Risk of shock is fairly minimal, but all electricity should be taken seriously. SPARK is a greater concern. 48V short circuited has the potential to create large sparks that can melt battery terminals and propel molten lead. Always wear safety glasses when working on batteries and battery connections.
I recommend covering the handles of your battery wrenches with shrink tubing. You get a nice snug grip on your wrench and greatly increase its electrical resistance. You could also use electrical tape, but that's just going to make everything sticky eventually.
Lifting and Jacking: Chances are, you will want your cycle elevated. It makes it much easier to work on, as it prevents you from bending over, and working from floor level. I recommend a motorcycle lift. A small, sturdy table can also make a good stand, but it's challenging to get the cycle on and off that stand safely.
Whether using a lift, jack, or stand, make sure the cycle is SECURELY attached to it with straps or some other means. An elevated vehicle could easily become unbalanced while working on it, falling off the stand, damaging the motorcycle or landing on you, your other projects, or someone you love.
Use your multimeter correctly. Many typical multimeters allow for you to test voltage, amperage, and resistance. To test amperage, you have to physically move one of the probes to a different jack on the multimeter. MAKE SURE YOU MOVE IT BACK when you are done with the amperage test. Even if you flip the control on the multimeter back to voltage reading, but forget to put the probe back in the right connection point, the next time you go to test voltage, you will melt the tip of the one probe off in about one billionth of a second. And it scared the bejeezers out of me. I mean you. In theory, if that happened, it would really startle you. So make sure you use your multimeter right.
Don't smoke: Smoking is a fire hazard. Especially when you take the gas tank off.
Don't drink alcohol while or before working on the project. It impairs judgement, and you might do something stupid. Likewise, do not drink, smoke, or do other drugs while RIDING. Go for a ride, come back, and THEN have your beer.
Step 2: Legal, Insurance, and Registration
Isn't getting insurance the last thing you do before you go on the road?
Well, yes and no.
You do NOT want to go through all the time and expense of building an awesome electric motorcycle, only to find that you can NOT legally ride it!
Some legal reasons you may not be able to legally ride your cycle in your area may be due to Registration, Insurance, or License.
None of these things are that complicated, but you must comply with whatever the rules are in your area. (If you have a large private property, and will not be using this vehicle on-road, you may be able to ignore this.)
Registering your cycle should be done exactly the same way any typical gasoline powered cycle would be done in your area. In some places, cars are required to pass a smog test, but motorcycles are exempt from that. A vehicle may also be exempt from certain tests or requirements if over a certain age (Classic or Antique) or primarily for show and exhibition or part-time use (Hobbyist.)
It seems that motorcycles are sold much more often WITHOUT a title than cars ever are. Make sure you get a title and bill of sale with the VIN - (Vehicle Identification Number) printed on it. If you do NOT get a title, make sure that you will be able to get one. This can sometimes require additional cost, paperwork, and/or vehicle inspection. Sometimes an inspection may require a matching number on the frame, engine, and transmission. Because of that, I recommend registering your vehicle as it is BEFORE removing the engine or transmission, even if it doesn't run.
A VIN is extremely important. I personally know somebody who built a pretty nice electric motorcycle from scratch. He made EVERYTHING on it, from the frame on up. He couldn't get it registered or insured. Without a VIN, registration may be possible (but lots of jumping through hoops) but extremely difficult. Without a manufacturer Make and Model, he couldn't get insurance. Eventually, he just took the cycle apart and used the parts on other projects.
By CONVERTING an existing motorcycle to electric, we have the VIN, Make, and Model to make the project fit "inside the box" for the government and insurance.
INSURANCE: One of the first things I did before really getting going on this project was to call my full-service insurance agent. I told her exactly what I wanted to do. Motorcycles are commonly modified and customized. This was really no different. I had no problems getting insurance. My insurance is about $100 a year and provided through Progressive.
Before starting your project, talk to an insurance agent. The year, style, or engine size of the motorcycle frame may dramatically effect your rate. A 1500cc crotch-rocket is likely to cost more than a 250cc standard cycle. Since you are removing the engine anyways, just get a cycle that you like, with enough room in it for the motor and batteries.
License: If you don't already have a motorcycle drivers license, get one. I signed up for a course at my local college. Besides being excellent training for a first-time rider, the class also gave a benefit of streamlining the process (and reduced the cost!) of getting the motorcycle endorsement at the Department of Motor Vehicles. Even if you are a long-time rider, an electric motorcycle will perform slightly different than an engine powered machine. Some colleges and other training centers also offer advanced and specialized rider training.
I have heard of people converting a small to medium sized motorcycle to electric and getting it titled as a moped. In that case, you do not need a motorcycle endorsement, but you can't legally carry a passenger either. You may also be restricted to which roads you can ride on.
Once again, make sure you check AHEAD OF TIME on all the legal requirements in your area for vehicle operation. It's pretty exciting once your electro-cycle is completed, and you'll want to be ready to hit the road!
Step 3: Donor Bike & De-ICE-ing
Besides just overall style and finding something that fits your budget, here's what to look for in the donor bike.
OVERALL GOOD CONDITION
It might sound obvious, but get something that's in fairly good condition. You want to do a conversion, not a restoration! Make sure the turn signals and headlight work. The horn should work. It shouldn't be all rusted out. Get something that looks nice enough and will be fun to ride. If you happen to be somebody who regularly builds custom motorcycles and restorations, just ignore what I said. Go hog-wild instead. I do have to admit that the cycle I bought to convert to electric was not in very good shape. The price was right though. In the end, fixing all the little things on it took a fair amount of time and work. Looking back on it now, I would have preferred to spend a little more money and and have had fewer things to fix.
SAVE MONEY WITH A BAD ENGINE OR TRANSMISSION
In this conversion, the original engine and transmission are NOT used. If you buy a motorcycle that is in pretty good condition OTHER than a bad engine or transmission, you might be able to get a really good deal on it. Just make sure to keep the engine and transmission with for a while to confirm proper registration.
SAVE MONEY WITH A GOOD ENGINE AND TRANSMISSION
If you choose to buy a cycle in good running condition, make sure to carefully remove the engine and transmission. Keep all the parts together, label everything, and keep it out of the weather. Sell the engine and tranny to make some money back on the purchase of the cycle.
DRIVESHAFT, BELT-DRIVE, OR CHAIN
Most motorcycles are driven by a chain, but some use a belt or even a driveshaft. Get a donor bike with a chain. This will give you the most flexibilty and efficiency. Chains are cheap, don't slip, and are easy to change gear ratios by swapping out an inexpensive sprocket. Electric motorcycles CAN be built with a belt or driveshaft, but it is more of an advanced project and has other considerations.
BATTERY AND MOTOR SPACE
You will want a cycle with enough room in its guts for the motor and batteries. A too-small cycle will limit where you can put the motor and batteries, and how many batteries will fit. An extremely large cycle gives you plenty of room, but the frame may become heavy quickly. Popular choices include sport bikes and medium-size standard cycles.
Sport bikes typically have an aluminum frame (light-weight) and it is shaped with two supports over the engine, and two under it. This gives you a "box" to mount your batteries. Sport bikes also usually have some sort of plastic fairing over the engine. After conversion to electric, you can put the fairing back on, and look almost stock.
A medium-size "standard" will have two frame supports under the engine, which can be re-used as a base or tray for mounting the batteries. You will most likely want to avoid any cycle that has a single piece of frame above or below the engine. It just makes it more difficult to find a way to mount the batteries. You can always fabricate something custom, but it's best to start with a solid foundation.
GET THE BOOK
Most cycles have a mechanics repair manual available for them. You might be familiar with the Haynes or Chilton's brands for car repair. Find the book for your cycle. Although it won't cover the new custom electric system, it will tell you how to fix your brakes, align the chain, painting tips, general repair and maintenance, and have plenty of other useful information.
Once you have your donor bike, you need to De-ICE it. ICE stands for Internal Combustion Engine. You'll be removing the engine, the transmission, and anything else related to that system. That includes the gas tank, the exhaust pipes, and a radiator if it has one. Remove these parts carefully, so you can re-sell them.
You will want to know where to put the electric motor for the conversion. The easiest way to do that is simply to put the electric motor exactly where the output shaft of the transmission was. Locate where the chain goes to on the transmission end and mark that location on the frame. Use a wax pencil or silver marker with a speed square to put a mark on the frame both vertically and horizontally from the output shaft of the transmission. You will later use these marks to position the electric motor.
Step 4: Electric Motor
To power your motorcycle, you're going to need a motor. But what type, what size, and where do you get it from!?
This project used a Briggs & Stratton Etek. It's a DC (Direct Current), brushed, pancake motor, rated at up to 48V and 150 amps continuous. I got it used, through Craigslist, from a college student who built those robots that battled each other. He was using this motor to swing a hammer, but it was too powerful, and he kept breaking hammer handles!
So why this motor?
DC - Direct Current
Direct current motors are very straight forward. They are easy to control the speed of. Also, batteries use direct current. By using a DC motor, there's no intermediate step of converting DC battery power to AC power to run the motor.
The Briggs motor has eight holes on the end (the "face") of the motor to make it easy to mount to a piece of flat steel or aluminum. Some motors have a "foot" on the bottom of them for mounting, which wouldn't have been as easy to use in this situation.
Permanent Magnet motors tend to be very compact. They create rotational energy (torque) by pushing two magnetic fields against each other. The one magnetic field is produced by current from the batteries (an electro-magnet). The other magnetic field is from mineral permanent magnets. These magnets are much more compact than a second electro-magnet would be, allowing for an overall powerful, yet small motor. The limiting factor in the design is the strength of the permanent magnetic field. Many permanent magnet motors spin equally well in either direction. Just swap the positive and negative battery cables for it to spin the other way. The permanent magnets are ALWAYS magnetic! So don't drop a washer near one of the vent slots, or it will get sucked in and you have to take the whole thing apart to get it out! Since then, I made sure ALL washers are stainless steel (not only are they corrosion-resistant, but they are non-magnetic as well.)
I chose this motor knowing that many other people had used the same one in their electric motorcycle designs. http://www.evalbum.com/mtrbr/BRIG
Permanent magnet motors are generally designed to spin equally well in either direction. If the motor spins the opposite direction of what you intended, all you have to do is swap the two cables. On a large motorcycle, you could take advantage of this with a reversing contactor to have a reverse gear.
It's not all about horsepower....
Electric motors are rated differently than gas engines are in terms of their power. A gas engine is rated in horsepower with the engine running at nearly maximum speed and fuel consumption (full-out!) An electric motor is rated at how much power is can put out continuously - for hours at a time. So, a horsepower rating between an engine and an electric motor is not apples to apples.
More and more engines are also now being rated in Watts. A watt is a unit of power used. Most people understand watts, as in that a 100-watt light bulb uses more power than a 75-watt lightbulb. It puts out more power (as light and heat) but also costs more on your electric bill.
In electric vehicle design, keep in mind that volts x amps = watts. Also, 1 Horsepower is roughly 746 watts. So, it's pretty easy to do some simple math to figure out the power of our motor.
By being connected to four 12V batteries in series, the system nominal voltage is 48V. The motor is rated at 150 amps continuous. 48 x 150 = 7,200 watts. Divide that by 746 (watts to horsepower) and you get about 9.6 horsepower. That doesn't sound like a lot. However, you can pull much higher amperage briefly through the motor - typically three or four times as much. My system amperage is limited by the fact that the motor controller maxes out at 300 amps. That still means we can get DOUBLE the power out of the motor compared to what you might think it can produce, just based on the numbers stamped on it.
Combine that with increased efficiency (by completely losing the transmission) and the fact that you have FULL TORQUE right off the line (a gas engine has to rev up to several thousand RPM to get into it's best power band) and even a compact electric motor has far better acceleration than you think it might.
I later had my cycle tested on a dynometer at a large Harley-Davidson gathering. The cycle "officially" clocked-in as 12hp. But when the guy first went to ride the cycle up to the dyno, he almost threw himself off with how quick it accelerated!
What other motors might you use in your electric motorcycle? Besides permanent magnet DC motors there are also Series-Wound and Brushless DC motors as well as some new AC motors. Series-wound motors are similar to permanent magnet DC motors. They are bulkier, but produce fantastic torque! You could use a series-wound drive motor out of a junked electric forklift. Do not use a pump motor. Those typically do not have a male driveshaft. Same goes for electric golf cart motors. They may otherwise sound like a good motor for a cycle, but unless you have a way to easily connect a standard sprocket to the motor, they will be a lot of tinkering to make work for your project. ( A friend of mine is currently working on designing a kit with a specialty part allowing anyone to build their own electric motorcycle using an off-the-shelf golf cart motor. Look for that in the future.)
Brushless DC and AC motors are very similar. They require dedicated controllers designed specifically for them. If you go that route, buy your motor and controller as a matched set through a reputable dealer.
in general, all these motors are air-cooled, so you don't need a motorcycle with a radiator on it.
For planning purposes, you want to know that your motor will FIT in the motorcycle before you buy it! Made sure to measure the space you have and the physical size of the motor before you buy. If the motor is not in front of you in person, don't worry, most mainstream manufactured motors have diagrams that you can download, that include the physical dimensions. (See Etek_Diagram PDF file attached below.)
Besides the diagram showing physical dimensions, it also lists important information on torque, voltage, RPM, etc. That helps you plan out your cycle design as well.
Step 5: Motor Mounting Plate
Once you have your motor selected and in-hand, you need some way to physically mount the motor where you need it to go in the motorcycle.
To do this build an "Adapter Plate" or "Motor Mounting Plate".
I built mine from a piece of scrap 1/4" aluminum plate that I had around. The plate needs to have a hole in the middle of it for the driveshaft to pass through and four holes in the appropriate locations for the bolts to mount the motor to the plate.
The plate also needs mounting points to connect it to the frame of the motorcycle. On this project, I re-used the existing mounting points in the frame of the cycle where the engine and transmission originally bolted in place. Those holes are already just about where I needed them and it meant I didn't have to make any new holes in the frame.
MAKE IT REAL
Rather than making a template from scratch, or drilling holes based on careful measurements of the motor, I simply made my own paper template based on the PDF file that I already had of the mechanical drawing of the motor. In a graphic design program, I simply made sure that the measurements on the diagram matched up to 100% actual scale, and printed it out on paper. The motor is compact enough that the whole image fit on one 8.5x11" sheet.
I cut out the piece of paper and then glued it (rubber cement) to the aluminum plate. Using a drill press, I simply drilled holes of the appropriate size (the size is marked right on the diagram!) right through the crosshairs on the piece of paper. That gave me a plate of aluminum with a central hole for the driveshaft, and four holes to mount the motor to the plate. I test-fit the plate in place on the motorcycle, with the drive-shaft hole lining up with the marks on the frame indicating where the chain originally went. I then sketched right on the plate "tabs" of where the plate would extend to the existing mounting points on the frame - one on the bottom and one on the high side of the back. I will later add another attachment point on the front with an angle bracket.
At that point, I could just put the motor and plate together to confirm that all the holes lined up. I also traced the outline of the motor on the plate.
Once I rounded off all the edges, I put the plate in the motorcycle, and ran threaded rods (3/8" and 5/16", which matched the holes in the frame) through the frame attachment points, through the plate, and through the matching attachment point. Stainless steel nylock nuts and washers went on both sides of the adapter plate and on the outsides of the motorcycle frame. If I ever need to adjust the position of the motor side-to-side, I can loosen the nuts on either side of the plate and move it one direction or the other.
Step 6: Batteries
This motorcycle is powered by four off-the-shelf batteries. They are Optima Yellow-Tops, rated at 55 amp-hour capacity, and cranking current of nearly 900 amps. They are AGM - absorbed glass matt. That's a style of lead-acid battery that is sealed up and the electrolyte is soaked into coils of fiberglass matting. They cannot leak, spill, or slosh around.
While there are other types of batteries available, this seemed to be the best combination of price and performance for my project. "Flooded" lead-acid batteries are really not acceptable for a motorcycle. Besides being challenging in adding water, the movement and possible tipping-over of a motorcycle would not be good for flooded batteries.
Sealed lead-acid batteries (VRLA) would also be fine, as would gels. However, neither of those can crank the power as well as an AGM can, which is what gives the cycle good acceleration. Lithium batteries are excellent for weight, capacity, and power, but are currently only for those with higher budgets. If you use lithium batteries, everything else about the project is the same, except for a different battery charger and a battery management system.
Going back to some simple math, we can get an estimate of motorcycle range. I have four batteries, each of which is 12 volts, but they are wired up in one series string of all four of them, so it's really 48V in total.
The batteries are rated at 55Ah.
So, in theory, 48V x 55AH = 2640 watt-hours capacity. 100 watt-hours per mile is a typical ball-park number for energy consumption per mile on an electric motorcycle. (Of course that does vary by weather, speed, riding style, etc.) But this is just a rough estimate.
2640/100 = 26.4miles
Just a real rough estimate, but it's good enough to say "Will this vehicle meet my needs? Will it perform the way I want it too?"
In this case, yes. I only live a couple miles outside town, and the next town is ten miles away. I can use this cycle to drive all over locally, and head to the next town over and back on one charge.
In real-world driving tests, the single-charge range of the cycle came to 23 miles if I drove full-tilt, and 32 if I was doing easy acceleration and in the city 25 mph zones.
Mock-ups and CAD
Lead batteries are NOT light. It helps to make a mock-up from foam or cardboard, so that you have a LIGHTWEIGHT, easy-to-handle version of the battery to experiment with. I like to think of this as the poor-man's C.A.D.
If you are into computer design, there are many great programs out there to help you create 3D images and think in three-dimensional space. Google Sketchup seems to be getting fairly popular. Still, you really can't beat an actual, physical object in your hands. I just prefer something that weighs less than lead.
In my earliest version of the cycle, I had three batteries in it. Then I moved up to four (for more range and higher top-speed.) I was never sure how to fit four inside the frame in a way that fit well and looked good. By using cardboard mock-ups, I was able to experiment with various arrangements of batteries until I found one that I liked. In this case, the fact that I could mount these batteries turned on end allowed me to come up with a configuration that I liked.
Once the size and number of batteries are decided on, they need to be physically mounted inside the motorcycle, and solidly connected to the frame.
Edit: Please note - Battery technology has been changing rapidly the last few years, largely in thanks to commercially-built electric cars. Lithium cell modules are SIGNIFICANTLY less expensive than when I built the Electric Kawasaki. At this point, if I were building an electric motorcycle, I would go directly to lithium cells. Please keep in mind that with Lithium, you need some sort of BMS (Battery Monitoring or Battery Management System,) and it needs to be charged appropriately. Please visit a web forum for the latest availability and best practices with Lithium Batteries.
Step 7: Battery Rack
Rack 'em up!
The batteries need to be securely mounted to the frame of the cycle.
This is typically done with a box shape or angle iron.
You do also want to keep in mind that the batteries are the heaviest part of the motorcycle. Ideally, they should be kept as close to the center of the cycle for front/back balance, and as LOW as possible for best center of gravity. Fortunately, that describes the big hole left by the removal of the engine and transmission.
The trick is to design a rack that fits in that space and holds the batteries.
A simple start.
In the earliest, experimental version of the motorcycle, I played around with something as basic as a "tray" put across the bottom two frame members. Small batteries could just sit right on top of that in a single layer. The larger batteries could only fit two there, so the others would have to be mounted in some other way. I experimented with "unistrut" - a slotted C-channel material available at building supply stores. It worked well in holding the batteries, but I didn't like the looks. The batteries stuck out the sides a bit in a way I didn't like.
Cut, Grind, Weld, Paint.
While the early version of the cycle was functional, I really wanted to get it cleaned up and looking nice. I had been practicing welding, and it was time to build a welded rack to hold the batteries.
The rack consisted of 1" steel angle, cut to make frames that fit around the batteries, and tabs that would reach from the battery frame to an existing engine mounting point on the frame of the motorcycle. It would be made of several "layers", because of the arrangement of the batteries - two on the bottom, and two mounted above them.
Essentially, there were four pieces:
- Bottom piece. Connects to the bottom of the frame of the motorcycle. The two bottom batteries sit on top of it.
- Lower-middle piece. This sandwiches down to hold the bottom batteries in place and connects to the front of the cycle frame.
- Upper-middle piece. Holds up the top two batteries and connects to the front of the cycle frame. Sits directly above the Lower-Middle piece.
- Top-Straps. These are just two pieces of steel that go over the top of the top two batteries to hold them down. Threaded rod goes through the ends to tie them down to the other parts of the battery rack. This is very similar to a typical tie-down for a car battery. (The top straps are insulated and don't go near the top posts of the top batteries.)
Besides just being a square ring under the bottom two batteries, the bottom piece also had to directly connect to the bottom of the frame. To do that, I ran two pieces of angle iron the length of the cycle's engine bay, so that it bolted right to the frame, again, through existing mounting points. It might be a little overkill, but gave me plenty of new attachment points for threaded rod to hold down the batteries, and another connection point for the motor mounting plate.
To figure the size of each rack piece, I simply put the batteries together the way they would fit, and measured them. I added just a little more to the measurement to give me some wiggle-room, and account for some thin weatherstripping to go between the batteries and rack when finished.
The tabs to mount the battery rack components to the frame were just flat steel - 1" wide. I put the batteries and rack parts into the frame and test fit the spacing between the rack and the frame and clamped them in place. Then I removed everything and welded the tabs.
On the back of the rack parts, I welded some short bits of steel pipe, just a little larger diameter than the threaded rod I was using. These are "holes" that the threaded rod goes through to align all the parts and sandwich them together.
All rack parts were were painted with Rustoleum gloss black paint and the assembled into the cycle.
The finished rack looks nice and holds the batteries securely. The battery arrangement keeps them inside the body of the cycle. I was originally hoping to be able to just exactly clear the gas tank. In the end, the pieces of angle iron added up to too much total thickness. I notched the edge of the gas tank to make it clear the top batteries. The gas tank is hollow and covers the top posts of the batteries.
Step 8: Charger
If you have batteries, you are going to need to charge them.
Chargers are fairly simple, but there are a few things to think about. Will you use one 48V charger, or 4 12V chargers? Will the charger mount on the cycle, or will you keep it in the garage? What about solar or other ways of charging?
12 vs 48
An electric vehicle is typically charged one of two ways, either one charger that charges ALL the batteries, or one charger for EACH battery.
It would be pretty simple to hook up one twelve-volt charger to each of the four batteries. (Or even just use one 12V charger to charge a battery, wait for it to charge, move it to the next battery, wait for it to charge.....WAY too time-consuming though....)
In my setup, the top two batteries aren't real easy to access to connect and disconnect battery chargers to. It would be fairly easy though to PERMANENTLY leave battery chargers connected to it.
There is some space under the hollowed-out gas tank, that could fit a battery charger.
To use a series-charger, ONE SINGLE charger of a higher voltage (48V in this case) charges all the batteries. You simply connect the positive cable to one end of the string of batteries, and the negative cable to the opposite end of the string of batteries.
A 48V charger has an advantage in that ONE charger tends to take up less space than FOUR chargers. Higher voltage chargers tend to be more expensive in general that 12V chargers (They just mass-produce so many 12V chargers that they are cheaper.) However, 48V is a common voltage for golf carts, forklifts, and electric scooters. Ebay and on-line electric scooter companies are great places to get 48V chargers.
Onboard vs Offboard
Where do you want your charger to go? My original 48V charger permanently mounted on the motorcycle, under the gas tank. It's plug was right on the frame of the cycle, and I would just plug an extension cord into it from the wall. The cycle would automatically start charging. A charger that's left always mounted to the vehicle is called an "on-board" charger.
On the other hand, you might have a charger that you just leave in your garage. It would have either alligator clips (similar to jumper cables) or an Anderson disconnect (a popular, fairly standard power quick disconnect.) When you park the cycle at home, you either plug in the connector or clamp on the alligator clips from the charger to the battery pack.
Both on-board and off-board chargers have their benefits.
On-board chargers are always with the vehicle. If you ride over to a friend's house, or have access to an electric outlet at work, you can ride there, plug-in, and charge the cycle the whole time you are there. Your charger is always with you. You can top off the batteries any time you want, even if they are just partly discharged, or even if you know you will only be charging for a little while. This is called "opportunity charging", and is a good way to extend your range and keep your batteries happy.
An off-board charger is NOT with you while you are out and about. That can be a good thing too. While you can't "opportunity charge", you also don't have the weight of the charger, nor do you need to have the SPACE on your cycle for the charger. In addition, some chargers are rather large and heavy, and you simply wouldn't want to try to lug one with on your motorcycle. You might also be able to get a really good price on purchasing an off-board charger. Also, an off-board charger is typically available for use on other things, such as recharging your car battery.
I originally started with a very compact 5-amp 48V scooter charger that I kept on-board of the cycle. Unfortunately, it was a poor quality off-brand that eventually quit working. After that, I put an Anderson disconnect on the cycle so that I could quickly connect and disconnect a variable-voltage off-board charger. That charger is big and heavy, and stays in my garage. It is variably voltage, so I can charge anywhere from 12-72 volts. When I am not using it to charge the cycle, I can charge my 12V car battery, or my 36V electric riding lawn mower. If I upgraded my motorcycle to 72V, I could still use the same charger and just turn the knob another two clicks!
How big of a charger?
People commonly ask how long it takes to charge an electric vehicle. Or the may ask how "big" my charger is. What they are really referring to is the rate of charge, which is measured in amps. Battery capacity is measure in amp-hours. When you want to know how long it takes to charge a battery, it depends on the capacity of the battery (and how far it is discharged) and the amp rate of the charger.
The basic math is pretty simple though. Lets say that you have a battery that is rated at 100AH, and it's half-empty. That means that you need to charge it with 50AH. If you have a charger rated at 5 amps, that will take 10 hours, or overnight. If you have a 10-amp charger, it will take 5 hours to charge, which might mean you could get a full charge while at work!
Consult your battery information. Battery manufacturers provide information on the preferred rate of charge and voltage points for their batteries. Get a charger that matches what your battery manufacturer recommends. In addition, some chargers are either pre-programmed or have a specific setting for a particular type of battery. If your charger has a setting for "Flooded" and another for "AGM", make sure you use the correct setting.
For a nice, short "rule of thumb" get a charger that has an amp-rating of 1/10th the capacity (in AH - amp-hours) of the battery. Mine are rated at 55AH, so a 5 amp charger will always recharge it in 10 hours or less.
I'm now using an off-board charger which is selectable between 5 and 10 amps. I added an Anderson connector to the battery charger and the motorcycle to make charging as easy as plugging in the connector, and flipping the charger switch to On.
There are other ways to recharge batteries as well. See the end of this Instructable for thoughts on Solar and Grid-Tied Battery Backups.
Step 9: Motor Controller and Throttle
With the motor and batteries in place, they could be cabled up, and the motor would spin, but how would you control the speed?
That's what the motor controller does.
Direct Current (DC) motor controllers typically all work the same way. They "chop" the current from the batteries to the motor. Essentially, they are a big fancy switch that turns power to the motor on and off very quickly, typically thousands of times per second. The controller varies how long the circuit is on vs. off, depending on the signal it gets from the electronic throttle, or "potentiometer".
The technique of turning the motor full on and off quickly is called PWM or Pulse Width Modulation. Besides controlling the speed of DC motors, it's also used to dim LEDs on sports scoreboards and digital billboards, and is also used in many other facets of industry and electronics.
By always providing the full voltage to the motor, but turning it on and off quickly, the motor has full torque (OOOOOMF!) at any speed. The speed of a DC motor is directly proportional to the voltage provided to it. More voltage (such as having more batteries in series) makes the motor spin faster. With PWM, the AVERAGE on/off of the pulse width modulation controls the speed. But there's still full voltage, and voltage times amperage = HORSEPOWER. Using a modern electronic PWM controller gives an amazing effect of all the power you want at even very low speeds.
There are other ways to control speed on battery powered DC motors. One older technique was to mechanically switch the series/parallel connections of the batteries to the motor in such a way that that it might be 12/24/48 volts. A bit like having "3-gears". These systems made a lot of clacking noise, and the contactors (heavy-duty power switches) needed maintenance somewhat regularly. The speed control was fairly basic. Vehicles like the Citicar made use of this type of system.
Voltage to the motor could also be controlled by running the current through a variable resistor. Trouble is, you need a BIG resistor! They get hot, and would need a LOT of forced air cooling. It would be a very inefficient means of control, as the only time all of the power goes to the wheels would be when you were driving full speed. (The rest of the time at least part of the current is being wasted as heat.)
PWM is a nice and efficient means of controlling speed, conserving energy, AND giving you excellent speed control. If it sounds complicated, don't worry, there's a PWM controller in nearly every electric golf cart out there.
In fact, a used golf cart motor controller from E-Bay might be a great place to start! Golf cart controllers are typically 36-48 volt, and are so mass produced, that they tend to be rather affordable. You will want to make sure to get one that has a high enough amperage rating to make the cycle fun.
Choosing a Controller
The two most popular brands of motor controllers are Curtis and Alltrax. I'm using an Alltrax AXE 4834 controller.
Because the motor controller is wired up between the batteries and motor, it is common for it to be one of the limiting factors of your electric vehicle's performance. The model of controller you want will depends on your system voltage (how many batteries you have) and the current you want to be able to pull. You typically want to minimize current while cruising, so that you are "sipping" power from your batteries, and in turn have a long range per charge. However, you want to have high current available to you for quick acceleration (half the fun of an electric motorcycle!) and powering up hills.
My motorcycle has a 48V system, so I purchased a motor controller that can run on anywhere from 24-48 volts. If you want to build a motorcycle at 48V and think you MIGHT want to upgrade in the future to 72V, you could get a motor controller that will operate from 48-72V, but it will cost you a little more up front.
My motor controller can pass up to 300 amps of current to the motor. The motor is only rated for 150 amps continuous, but can briefly take much more than that. The batteries themselves can produce nearly 900 amps (briefly), but the electric motor simply can't pull that much power.
If you just want a moped type vehicle for around town use, a 175 amp used golf cart controller will be fine. If you want to have good acceleration, get a 300 amp controller. A 450 amp controller should give enough acceleration to keep pretty much anyone happy!
Once you get into higher voltage and amperage, controllers start to get expensive. A popular one for an electric car is about $1500. If you built your own, you could have the best of both worlds - a high power controller at an affordable cost. But where would you start? How about right here on Instructables! In fact, here's a controller anyone can build themselves that's good for up to 100 electric horses. https://www.instructables.com/id/Homemade-100-HP-Motor-Controller-for-an-Electric-C/
That's the motor controller that currently powers my homemade electric car.
Mounting the controller
The motor controller needs to be mounted solidly to the frame of the cycle, near the batteries and motor. It does produce a small amount of heat, so ideally the controller should be either out in the airflow, or if you have an aluminum frame, just pressed right up against that.
On my cycle, the best place for the controller was behind the batteries and above the motor. This kept the power cables short and everything was still easily accessed. It also shows the controller off nicely, as people often ask me how the vehicle works, and it's nice to point out the various components.
I used a scrap aluminum plate to the mount the controller. Aluminum makes a nice heat-sink, and it's lightweight and easy to cut and drill. The controller has four mounting holes on its base. I marked and drilled matching holes on the mounting plate, and attached the controller with typical nuts and bolts. Adding that plate to hold the controller also gave me room on the OTHER side of the plate to mount the "balance of system" components.
The throttle is a "potentiometer" - a variable resistor that sends a signal to the controller, based on its rotation.
I used a Magura Twist-grip, a popular throttle that replaces the right-hand grip on a scooter or motorcycle. On my cycle frame, the original throttle was rusted and the throttle cable was broken. I removed the original throttle and slid on the Magura Twist-Grip. It easily installs just by sliding it on and then tightening a pair of screws to snug it onto the handlebar. (Had my original throttle been in good condition, I could have just connected the throttle cable to a different style of potentiometer, such as a PB-6.)
The throttle comes with three bare wires, but there are only two connections for throttle on the controller! What do you do!? Well, since you just mail-ordered this part, you can call the dealer and ask which two wire you use. Otherwise, you can test them with the OHMs setting on a multimeter. Potentiometers have three connectors or wires. The center one is the "wiper" which changes as you turn the potentiometer. The other two wires are the "ends" of the range the potentiometer covers. One is high and one is low. Connect the Ohmmeter to two of the wires, and twist the throttle and see if the reading changes. When it reads 0 ohm when just connected, and 5000 ohms when fully twisted, you got the right two wires. Crimp a 1/4" insulated spade connector to those two wires. Cut or fold back the third wire and cover it with electrical tape or shrink tube.
Route the throttle cable from the handle-bars, along the body of the cycle (leave slack for steering!) and back to the controller. Plug both wires into the connectors marked THROTTLE. Polarity doesn't matter, plug either wire onto either connector. Make sure they are on securely. As a safety feature of the controller, if the throttle ever becomes disconnected, the controller shuts down.
Wiring up the controller power cables to the motor and batteries is fairly straight forward. The motor controller comes with a manual that includes the wiring diagram. The Alltrax Document Depot is a great resource for all sorts of information on controllers, batteries, and motors.
After the cycle is completely finished and test-driven, you will want to tweak the controller. Some controllers have small potentiometers on the side that are adjusted, and others are computer reprogrammed. The Alltrax AXE lineup has a computer port. You simply plug a cable from the controller to your computer, download a small program, and change parameters through a simple interface. On most controllers, you can control throttle response, limit maximum amperage, and control voltage shut-off points. On an electric motorcycle the "feel" of the throttle is based on how the controller is tweaked.
Step 10: Balance of System
Balance of System is a fancy term that refers to "and everything else".
In an electric vehicle, you already know about the main components, like the motor and batteries, but it can sometimes be the little things that people don't talk about, and can be the most confusing.
In this case, we will talk about the on/off key, main fuse, contactor, battery disconnect key, pre-charge resistor, shunt and ammeter, instrumentation, power indicator light, and DC/DC converter. Most of these components are shown right on the wiring diagram, along with their specs.
When I got my cycle frame, the ignition key was broken. I replaced it with a simple keyed electrical switch. It's a "double-pole, double-throw" switch, which means that it completes two separate circuits at the same time. That's great, because with one switch, I can turn on both the 12V accessory system and the 48V drive system at the same time.
I built a mounting bracket by cutting down a piece of metal from a recycled computer case. I drilled a hole to mount the key switch, two holes for bolts to mount the bracket to the cycle frame, and painted it black. The switch gets two sets of wires to the back of it, both with small crimp-on ring terminals. One set goes to the DC/DC converter to run the 12V accessory system, and the other pair activates the main contactor for the 48V drive system.
On a motorcycle that has an existing, working ignition key, you can route 12V power from the key to activate a relay that will turn on the main contactor and motor controller.
The battery disconnect is just a big kill switch. It completely disconnects the batteries from the rest of the system. It's an easy way to disconnect power for when you are working on the cycle, and acts as an emergency backup in case the main contactor ever failed. Both the On/Off Key and the Battery Disconnect are mounted on the left side of the motorcycle, not far from where the "Emergency Reserve" switch would be on a typical cycle's gas tank. Since there is no clutch or other left hand control, these are mounted on the left side in easy reach of the rider.
The batteries are connected or disconnected with a removable red "key" plunger. Make sure to get a disconnect rated for high amperage. The full current of the vehicle goes directly through this component. All battery cables, fuses, connectors, shunts, shut-offs, and anything else carrying current needs to be sized correctly. Since I'm using a 300 amp motor controller, sizing everything to 300 amps makes sense.
The bike needs a fuse that will blow and protect the system if anything shorts or otherwise draws too much current (such as a blown motor controller.) I used a fancy-looking fuse holder with a 300 amp fuse in it. Make sure to mount this in such a location that the fuse is easy to access and replace. (If you want to get really wild, make it so it can be easily replaced on the side of the road, in the middle of nowhere, at 4AM in a rainstorm. Because you just KNOW that's when you are going to have a problem....)
The Main Contactor is a large, remotely-activated, high-power relay. When I turn the on/off key, it sends 12V to the main contactor, which closes, and completes the 48V drive circuit. The contactor is spring-loaded, so that if it no longer gets that small amount of 12v power, it opens and shuts down the cycle. This works well as a safety feature. For example you could wire a switch in series with the 12V power to the contactor from the kickstand. If the kickstand is down, the main contactor won't close, and you can't turn the cycle on.
Most motor controllers require a "pre-charge resistor". That's a way to allow power to slowly go into the motor controller to charge up the capacitors. If power was suddenly applied to the motor controller (such as just flipping a switch) the capacitors internal to the controller would suck up power almost instantly. Do that too many times and the capacitors will blow and wreck the controller. If you called the manufacturer for warranty work, the first thing they will ask you is about the pre-charge resistor.
The resistor simply bypasses the main contactor. When the battery disconnect is turn on, current will flow from the batteries, through the resistor, and into the controller. As it does, the voltage internal to the controller will raise to match that of the batteries. Once it does, you can turn the key to on, which activates the main contactor. The contactor is now a less resistive path, and when you twist the throttle, high current can not go from the batteries, through the contactor, controller, and motor, and drive the cycle. Pre-charging the controller also prevents any arcing internal to the main contactor and prolongs its life.
Ammeter and Shunt
The ammeter is a display of how much current (measured in amps) that you are using at any given moment. Think of it as a real-time energy meter. In general, you want to minimize amperage while cruising (to maximize range and battery life) but it would also be nice to know how much power you use for burn-outs and powering up hills.
This is usually a matched set. The Ammeter is the display itself, mounted on the handlebars or other location for easy viewing, and the shunt, which is a calibrated piece of metal that the current flows through. Two wires (one on either end of the shunt) go to the ammeter. The needle on the ammeter varies directly with the amount of current through the shunt.
My ammeter is a 300 amp meter, mounted in a hole in the former gas tank. The shunt is mounted out of the way, near the contactor and battery disconnect. I strapped the gas tank down to a drill press with a hole saw in it to cut a hole just slightly larger than the ammeter. Since the gas tank doesn't hold gas anymore, there's no reason not to cut holes in it and mount instrumentation in there.
I recommend an ANALOG ammeter. A needle sweeping back and forth is easy to quickly read. Although a digital display may be more accurate, it's not as useful and it's difficult to read digital numbers that are constantly changing.
Power Indicator Light
On an electric motorcycle, there is no engine noise or vibration to indicate to the rider or anyone else that the motorcycle is on. You simply flip a switch, and it's instantly ready to go. Although the headlight is on when the cycle is on, the rider typically can't see that during the day. I wanted a great big, bright indicator to tell me when the vehicle was on. I decided that a green light mounted towards the front of the tank would work well. I found some switches, lights, and other components on an old instrument panel. One light had a sign on it saying "Power" and another one had a green lens. Both lights were for AC power, not DC power. I grabbed the components and put together the green lens, the power sign, and removed the small transformer on the bottom of the light socket so I could instead run 12V DC straight to the bulb. The bulb holder was installed through the gas tank, and 12V wiring run to it from the cycle's 12V fuse panel.
Powering the 12V system
On a typical gasoline motorcycle, there is a 12V battery to start the engine and run the headlamp and other electrical. The battery gets recharged by the engine, through the alternator, and it is what really powers all the 12V electrical.
Without an engine and alternator, you will need some other way to run the 12V electrical.
With a 12V battery
If you mostly just use the cycle for very short trips and errands, you could just use a plain, sealed, 12V battery. That battery would need its own charger, so that every time you are done with a ride, the 12V accessory battery gets recharged right away. The battery will take up some space, add some weight, and you would most likely want the charger for it left right on the cycle as well, using up even more space. It does work, and is simple, but not ideal.
With a DC/DC converter
Instead of a dedicated 12V battery and charger, you could use a DC/DC converter. The converter is an electronic device that takes one DC voltage in, and gives a different DC voltage out. It's a very efficient way to use a trickle of power from all four of the large drive batteries, convert the 48V to 12v, and run the headlight and other accessories.
The DC/DC converter was a computer component purchased from e-Bay for $10. It's two-inches square by half an inch thick - very compact and lightweight. This saves considerable bulk and weight over a medium-sized battery and dedicated charger. 48V from the drive batteries is wired to the input end of the converter. The output end of the converter takes the place of a 12V battery. The + goes to the cycle fuse panel, and the - goes to the motorcycle frame ground.
The output of the converter is adjustable into the range of CHARGING a 12V battery, so another option is to use BOTH a DC/DC converter and a small lead-acid battery. The converter provides power to the battery as a trickle-charge, and the battery acts as a reservoir in case you suddenly pull more power than the converter can provide, or in case it quit working.
This DC/DC Converter is rated for 100 watts. The headlamp draws 55, leaving plenty of power for the tail-lights, turn signals, and other 12V accessories.
I crimped and soldered 1/4" spade connectors on the converter to make it easier to quickly connect the wiring. The converter already has mounting holes in it. I mounted it with small screws to the same plate that the motor controller is mounted to.
All over these various components serve important roles. Even though the motor and batteries are the first things we think of on an EV, make sure you understand the balance of system to properly and safely operate your vehicle.
Step 11: Driveline, Sprockets, and Gear Ratios!
I bet by now that you want to make the cycle go!
So, it's time to talk about the driveline.
This motorcycle is about as simple and efficient as you can get. It's more or less the same as a single-speed bicycle.
The motor has a drive sprocket, which connects to a chain, which turns the back wheel. That's it!
The motorcycle uses a standard machine sprocket. I simply went to a farm store, which had a decent tractor repair aisle and located parts for the sprocket and chain. I bought a 14-tooth sprocket and a hub with a 7/8" center hole to match the motor's drive shaft. These are two parts, bought separately, which allows greatest flexibility in driveshaft diameter and sprocket tooth count. The sprocket and hub had to be welded together. In the earliest version of my cycle, that was the only welding done on the entire project. It was only later, when I had some welding experience that I tackled the welded battery rack. On the original sprocket, I just had somebody else weld those two pieces together for me. They were inexpensive - under $20 for both parts. If I want to change the gearing on the cycle, all I need to do is spend another $20 at the farm store and get a sprocket with a different number of teeth. These same parts could also be mail-ordered from a dealer such as Grainger or other industrial supplier.
The sprocket slides onto the end of the motor driveshaft, and is held in place by a keyway, square key, and set screws.
The chain is #40 chain from tractor aisle. Cost about about $10 for ten feet, and a few dollars for a master link. It is a popular size chain, so there is a wide variety of sprockets that match.
I did not use the stock sprocket on the back wheel of the motorcycle. Electric motors tend to work best spinning faster than gasoline engines, and geared down a bit more. This gives you plenty of power, without constantly running high current through the motor.
There are many on-line motorsports companies that will make custom rear sprockets. I used one called Sprocket Specialists. You simply tell them what motorcycle you have, what chain you want to use with it, and how many teeth you want on it. They custom make them on CNC equipment and send it to you in the mail.
I got an aluminum sprocket for a Kawasaki KZ440 for #40 chain and 72 teeth. It has a black protective finish. The larger aluminum sprocket weighs less than the stock steel one did. (Saving weight is always a good thing for electric vehicles.) I removed the rear wheel, unbolted the stock sprocket, and replaced it with the custom one. Consult the cycle's repair manual to make sure to bolts are torqued correctly, and that the back wheel is re-installed right.
(Somebody asked about the sprocket being aluminum, and that this is a high-wear item. The black finish on this sprocket is a wear-resistant coating. The sprocket manufacturer highly recommend at least that for protecting the sprocket. I've been very happy with it, and wear on the sprocket has been minimal overall.)
After all of my riding, I believe that I COULD have kept the original stock rear spocket. It would have given me a higher top speed, poorer acceleration, and cause the motor to draw more amps. Most of my riding is in the city, so I would gladly have a lower top speed in exchange for better acceleration and less amp draw. By having the larger rear sprocket, I can always change out the inexpensive front sprocket to change gear ratios. If I kept the smaller stock rear sprocket, I wouldn't have had that flexibility.
My current setup is a 14-tooth front drive sprocket and a 72-tooth rear driven sprocket for a 5.14:1 gear ratio. On my cycle, I'm very happy with the combination of range, acceleration, and top speed. On a fresh charge, I have just enough power to do a minor burn-out. Acceleration away from a stop for city use is very nice. There's no clutch to slip or engine to rev, so the cycle just GOES the moment you twist the throttle.
Tweak the Driveline
Once I had the sprockets on, I wrapped the chain, checked it for length, cut it to length, wrapped it on to both sprockets, and closed it up for a brand new master link. (Make sure the clip on the master link faces the right direction. It can work its way off if you put it on backwards.)
The original chain guard still fit over the new (larger) rear sprocket, but just barely. I simply bent it a tad to make sure it had clearance.
On the front end, the transmission would normally have an integral cover over the chain and drive sprocket. Without the tranny, it meant I had to make a custom chain cover. It could have been made from almost anything - metal, plastic, wood, but I wanted to show off how the cycle works, so I went with plexiglass. I roughed out the shape required with some cardboard and a pencil, and then cut the plexiglass to fit the space. A straight piece of plexiglass covers the top of the chain. I used a scrap of an aluminum rail as a spacer between the motor mounting plate and the plexiglass to hold it in position.
With everything in position. The chain needs to be tightened and aligned as per the user manual.
While I had the rear wheel off, I also used the opportunity to put on new tires. (Bought on sale during a close-up sale!)
Step 12: 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.
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.
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.
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.
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.
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.)
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!
Step 13: Test and Ride
Before you go for your first ride, you must test the vehicle.
Make sure all chain guards and any other safety features are in place.
With the rear wheel OFF the ground, turn on the main battery disconnect and the key. Gently twist the throttle. The motor will start to spin, and along with it, the chain and back wheel. (If it doesn't, power down the cycle, disconnect the batteries, and follow the motor controller troubleshooting guide. It may be something as simple as a loose throttle connection. Most controllers have a troubleshooting indicator light on them to help you.)
Having an assistant turn the throttle will more easily allow you to inspect the cycle with the motor running. Visually inspect the chain alignment and the front and rear sprockets.
Everything else should also work on the cycle, the light, horn, turn signals, etc.
If there is anything else you need to do (chain alignment, torque bolts, etc.), power down the cycle and disconnect the batteries before working on it.
Make sure to take it easy on your very first ride. An electric motorcycle will behave a bit different than a typical gasoline cycle. Empty parking lots and lightly traveled roads are good for your first ride. As you ride, take note of anything unusual. The cycle should be very quiet and have almost no vibration, other than the bumps in the road. On my first ride out, I noticed that I didn't like the way the throttle responded. It was too touchy. Any tiny twist of the throttle would instantly begin accelerating.
When back from your test ride, check the cycle over again. Make sure nothing has loosened up, that the motor isn't hot, or anything else unusual. At this point, you might want to adjust the controller so that the throttle better suits your riding style.
If everything checks out, and the throttle is how you want it, CONGRATULATIONS! You just built your own electric motorcycle!
Step 14: Other Notes
In the list of "odd things nobody ever tells you about....."
I found a few quirks while working on this project.
Rear Brake Spring Bracket
When I was getting the cycle all back together and testing to make sure everything was working right, I had to hook the rear brake back up. On a motorcycle, the rear brake is activated by a right-foot pedal. A spring pulls that pedal back up when you release it. But here's the weird part.... I couldn't figure out where that spring connected to on the frame of the motorcycle. I consulted the repair manual, and found out that the spring hooks on THE MUFFLER!
By converting my motorcycle to electric, I no longer had a place to connect my return spring! So, I built a little tiny, custom bracket, just for the spring to go to. On your project, you might come across some other odd quirk like this. It's not a big deal, it just gives you the opportunity to be creative and come up with your own solution!
The Gas Tank
Some of the most common questions I get about an electric motorcycle are about the gas tank. Typical is "If it doesn't have any gasoline, why do you have the gas tank?" and "Why don't you just STUFF that gas tank full of batteries!?"
The short answers are that motocycles just don't look like motorcycles without the gas tank, and you really can't fit batteries in there anyways.
When I got the motorcycle, the tank was already rusted and dented. It was completely bone dry, but I still left it open for a few days before cutting off the bottom with an angle grinder, so I could beat out the dents from the inside. Then I stripped the existing paint, and gave it a new paint-job. The top part of the motorcycle frame is a tube that goes straight through the gas tank. The tank is almost like a saddle-bag that hangs over that bar. The tank is also curved and batteries are nearly always big rectangular things. So, between the frame and shape of the tank, you just AREN'T going to cram batteries in there (That would also raise the center of gravity on the cycle as well.) The tank does make an excellent cover for over the batteries. It would also be a good place to mount the motor controller or a battery charger, as long as you make sure they have enough ventilation.
Some electric vehicle enthusiasts will even make a FAKE gas tank from foam, fiberglass, or plastic. It gives the cycle that cool look, but since it's custom, can be designed to accomodate batteries or other components. Remember, on some cycles today, the "gas tank" really isn't. On Goldwings, the "tank" is just a filler port, but the actual fuel tank is elsewhere on the vehicle. The "tank" makes a nice box for gloves, goggles, and maps.
LOUD PIPES SAVE LIVES
One myth of an electric motorcycle is that it's silent. It isn't - it makes some noise, but it is SIGNIFICANTLY quieter than a gas motorcycle, especially one with modified tailpipes. Should the need arise for my cycle to be loud, I have a horn and am not afraid to use it.
Even though most car drivers today have their windows rolled up, with the air-conditioning cranked, and the radio blaring, (so they can't hear a thing anyways) some people still think that a motorcycle being obnoxiously loud is a safety feature. After the millionth time that I heard that "loud pipes save lives" (mostly from NON-motorcyclists), I wondered if there was a way I could play with that in a way that an electric motorcycle could be BETTER than a gas one when it came to making noise.
I connected an MP3 player to my computer and downloaded some various motorcycle sound effects. I then attached self-powered computer speakers inside the hollowed gas tank and bungie-corded the MP3 player to the handlebars. I could now sound like a Harley, a Kawasaki, a 50cc scooter, or the George Jetson flying car!
See details on that here on Instructables.
If you haven't already, take a riders safety class. Motorcycle riding is a skill. It should be learned and practiced. Make sure to always "get the hang of it" again in the spring after pulling the cycle back out of winter storage. Come to think of it winterizing should be covered here as well.
When I looked through the cycle manual on winter storage, I was surprised at how much work it was to store a gas cycle for the winter! You have to change the oil, run the tank dry, and doing a surprisingly-long list of other things! When back out of storage in the spring, you are supposed to change the oil (again!) and have another laundry list.
On my electric motorcycle, here's how I put it away for the winter.
- Charge the batteries
- Pull out the battery disconnect
- Ignore the cycle for the rest of the winter (I just keep mine in the back corner of the garage.)
In the spring, it's
- Charge the batteries (they will self-discharge a bit over the winter)
- Check the air in the tires.
- Put in the battery disconnect, turn the key, and ride the cycle!
A vehicle becomes more efficient the lighter and more aerodynamic it is. You can also help make it more efficient by reducing electrical loads. For example LED lights consume less power than incandescent ones. On my cycle, I replaced the stock taillight with an LED light from the autoparts store. They are mass-manufactured, DOT-approved, and affordable.
I'd like to have a low power-draw headlight, but at this time there are only a few DOT-approved LED headlights available on the market, and they are rather expensive. I'd like to get one when the price comes down, or possibly build my own.
The turn signals on the cycle are still incandescent, as they use nearly no power at all (how often are turn signals on!?) It didn't make sense for me to spend the money to upgrade them to LED. If I were building a new, custom motorcycle, I would install LED lights all the way around right from the start.
300 Miles per Gallon!
Another really cool thing about electric motorcycles is how crazy efficient they can be! After my first ride on a fully charged battery, I recharged the battery, tracking how much energy was used (with a Kill-a-Watt energy monitor) and divided it by how many miles I traveled (using the trip odometer.) I used electric-to-gasoline-conversion numbers from MIT to calculate what the equivalent "miles per gallon" would be. It came out to over 300 mpg!
Is it fair to use MPG when talking about electric vehicles? No, not really. Gasoline can't be made from wind turbines or photovoltaic panels, and there aren't nearly as many gas stations as there are electric outlets. When talking about electric vehicles, we might use "MPGe" or miles per gallon equivalent. It's not a perfect analog between gas and electric, but it gives people who have lived in a world of miles per gallon a better sense of the efficiency of an electric vehicle. Keep in mind that heat, noise, and vibration are all signs of POOR efficiency. An electric motorcycle doesn't have a hot engine, with noisy exhaust that needs mufflers, and it doesn't shake from engine vibration.
Many people are now familiar with the concept of regenerative braking, due to the mainstream popularity of hybrid cars. So, of course they ask if my cycle has it as a feature. No it doesn't. Although a DC permanent magnet motor can make a fine generator, adding regenerative braking adds to cost and complexity of the project. Also, most braking is done on the FRONT of a vehicle. On the cycle, the motor is connected to the back wheel, where it would be less effective for regen. Also, overbraking on the rear of a cycle can lead to a uncontrolled skid. Many "hypermilers" get better fuel economy by avoiding braking in the first place, using simple eco-driving techniques, such as "timing lights".
We wouldn't want to finish talking about this project without mentioning what it cost to build. First, let me start off by saying that any project like this can have WIDE VARIATION in the cost of the components and the final budget. On my project, some of the parts, like the ammeter, power indicator light, and battery charger were items that I already had or were salvaged materials.
Here's a basic run-down of the project budget.
- Donor bike - $62 (bought it for $100, sold scrap parts for $38)
- Motor - $500
- Motor controller - $300
- Twist Throttle - $50
- Batteries - $700
- Drive Sprocket - $20
- Chain - $10
- Custom Rear Sprocket - $100
- Fuse, holder, battery cut-off, and cabling - about $100
- Repair Manual - $20
- Main contactor - $50ish
Add it all up, and the project came out to right around $2000. If a person already had some other parts, tried used batteries, or installed an inexpensive forklift motor, the price could come down. (See Russ' cycle photo in the last step! He built his for nearly nothing!)
On the other hand, if it was all brand-new parts, with a high-end motor and controller, and lithium batteries, the project could easily be $10,000. (Check out Tony's cycle in the last step!)
On the electric car project, I was a bit smarter about money, creatively used salvaged parts, and built an entire electric car for about $1300 total.
Cost of charging
Electric motorcycles are efficient and have smaller battery packs than electric cars. My cycle usually costs about a penny a mile to charge. That will vary a little bit depending on what electric rates in your area are. Electric rates are much less volatile than gasoline prices.
If you have solar, you can charge your cycle for "free"!
In some areas, a "Time of Day" plan is available. You pay double the price of electricity during "peak load" times and you pay HALF the price during "off-peak" times, usually at night. Check with your local power company. By recharging your vehicle only at night, you can cut your electric "fuel" costs in half!
Lastly, I'd like to mention that even though I went into a lot of detail on this project, Electric Motorcycles are SIMPLE. They really are just about cleanest, most straight-forward transportation possible. Knowing what I know now, I could build an electric motorcycle in a three-day weekend.
I know one guy who I mailed a photo of my motorcycle to. When I saw him the next week, he had already built an electric motorcycle almost exactly like mine!
Step 15: Power Your House in a Blackout With Your Electric Motorcycle
We now have a completed electric motorcycle.
That's great for practical local transportation, but what about the 22 hours a day that the motorcycle is just parked there!? Isn't an electric vehicle just a big battery pack with wheels? Wouldn't it be great to in some other way make use of that?
A lot of very clever people think so. They are working on something called "The Smart Grid", in which electric vehicles only charge up at a time that little power is being used, and the EV PROVIDES it to everyone else when too much power is being used. It's just theory right now, and requires a lot of standardization of components, fancy computer controls, and vehicle owners agreeing that everyone else can "borrow" their power. It's a really neat concept, but I don't think it will happen anytime soon.
Could some of those same ideas be used on a personal level?
The Poorman's Smart-Grid
One use that would be fantastic for an electric vehicle is for home blackout protection. Instead of purchasing a gasoline or diesel generator for use in a power-outage, just run your house off your electric motorcycle!
UPS delivers for you
You might be familiar with a UPS (Uninterruptable Power Supply.) People often have their computer at work plugged into one. In a brief blackout, the UPS switches power over to an internal battery, allowing you to finish what you are doing and save your work. When the power comes back on, the UPS switches seamlessly back to regular wall power and recharges the internal battery.
While most basic UPSs are 12V, larger ones, such as for computer server rooms, often run on 48V. Hmmmm - that's the same voltage as the electric motorcycle. I spoke with a local computer recycler and asked if he ever gets 48V UPSs coming through his facility. He said that he did, but I wouldn't want it, as the batteries are always bad. I told him that not having batteries was no problem! It wasn't long until I got a call saying that a salvaged 48V UPS was in. I was able to get the salvaged UPS at no cost to me.
I mounted the UPS in a cabinet in my garage. It had been a while since my cheap, imported onboard battery charger had quit working, and I was using a basic off-board charger since then. Because of that I already had an Anderson quick connection on the motorcycle. I wired the UPS connection that would normally go to internal batteries to instead go to a matching Anderson connector. That way, I could quickly connect and disconnect the cycle from the UPS.
Keep in mind that a UPS is actually two things, a battery charger, AND a high-quality power inverter. By simply plugging the UPS into the cycle, it begins to recharge, and acts as a typical 48V battery charger.
If AC wall power is cut off from the UPS (such as happens in a blackout) it stops charging the batteries, and instead takes DC power from them and converts it to 120V AC power as is typical in American homes and businesses. The back of the UPS has several 15 and 20-amp outlets. That would be fine if I only wanted to power a few items directly plugged into the UPS. What if I wanted to run the whole garage off it, or my entire house!?
To do that, I first added an additional 20-amp circuit to my garage circuit breaker box. (The garage is separate from the house and has its own dedicated 100-amp, 240V breaker panel.) Connected to that circuit, I added what would become a power "inlet". Instead of electricity going OUT from the breaker box there, it would input to the breaker box there. This is called a "load-side connection".
(If you have specific electrical codes, or are required to use only licensed and certified electricians, don't mess around in your breaker box. High-voltage AC power is potentially fatal. Don't screw around if you don't know what you are doing!)
The new power inlet is a "twist-lock" connector. It is physically different than anything else in my garage, so a person can't plug anything else in there by accident. It is also labeled as UPS POWER INLET on the connector and in the breaker panel.
I built a custom cable with two male ends. One is a 20-amp plug (one blade is turned 90 degrees from a typical 15 amp plug) and the other is the twist-lock connector, which is rated for up to 30 amps.
I connected the cable from the UPS to the twist lock wall "inlet". On the breaker box, the mains circuit breaker is manually turned off, and the 20-amp breaker for the UPS blackout protection is turned on. That allows power from the motorcycle batteries to go through the UPS, get converted to AC power, and feed all the other circuits in the breaker box. My garage is now "off-grid"! I've run the radio, garage door opener, lights, and shop vac, and other power tools from the UPS. The UPS is rated for 2200 watts, enough to run any heavy corded drill or other shop tool.
The UPS only outputs 120V power, NOT 240V power. I do not have any 240V appliances (such as an electric oven or water heater) in the garage or the house. The garage only has two circuits, and both of those are on the same "leg" as the UPS.
If I wanted to run power to the house from the garage. I would turn off the main power to the house from the grid, and turn the circuit breaker (100 amp, 240V) from the garage to the house back on. It is illegal and dangerous to provide power to your house with it connected to the grid when grid power is down. Solar "grid-tie" connections have "anti-islanding" features, and generators use an "automatic transfer switch" to disconnect a residence from the power grid during a blackout. This manual system could be upgraded in the future with an automatic transfer switch or an appropriately designed system of relays.
So far, I have tested the system many times, both charging the motorcycle with the UPS and running my entire garage on just battery power. I haven't yet optimized my house circuits to put all the critical circuits (furnace, well pump, refridgerator, main living space lights) onto just one power leg, but we haven't had any blackouts yet either!
An IDEAL Poorman's Smart Grid would also have PV (photovoltaic) solar panels, a solar charge controller, an AC grid-tie, and device to switch from charging the 48V batteries, to running power back into the grid when the batteries are fully charged. 48V is a common voltage for many solar panels and solar charge controllers. With an electric vehicle connected to a garage power hub, the solar panels will charge the batteries, and the UPS will be available for household power backup. All of this could be done for only several hundred dollars in off-the-shelf parts.
PS: For more on this, I did produce an Instructable just on this aspect of the project
Step 16: Now You Make One!
Ok, I showed you what I made!
Now YOU build one! Make sure you post some photos when you are done.
If you want a high-speed, long-range vehicle, everything I've talked about here still applies, but you will need to use lithium batteries, which will add considerably to the budget. That said, they are fantastic, and lithium cycles are an absolute BLAST to ride!
If you have any questions about my project, please leave a question or comment below, or swing by my clean transportation blog.
For even more inspiration, take a look at these photos of electric motorcycles built by my friends.
You can read more about the lithium cycle shown here at Tony's blog. For information on Russ' no-budget DIY cycle, please visit his web page.
For more on my electric motorcycle and other projects, including ordering the BUILD YOUR OWN ELECTRIC MOTORCYCLE instructional video DVD, please visit 300MPG.org