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.
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.