Kawi2strokes.com Forum

For some reason, I have the urge to build an electric motorcycle and do it on the (relatively) cheap. I don't care about saving the planet, lower energy costs, or any of that other hippie stuff, I just think it would be neat to play with. The plan in my head calls for a small bike, something around the size of my KH100('cause small bikes are awesome ). Since all my RCs are electric, I've got a pretty good handle on electric drive systems. I can build my own brushless motor out of an alternator for next to nothing, and brushless controllers that are large enough are reasonably priced(in the $300-$400 range for something with regen capabilities). It needs to be capable of 60 MPH with a 50 mile range so I can use it as a work commuter, and the problem I'm running into is batteries. While I'd like to use Lithium batteries, I just don't have the budget for that many of them. All the lead acid builds I've read online only have a range of 20-30 miles with four AGM car batteries, and that's not going to cut it. Anyone have any experience with this sort of thing?

I don't know much about them but I think you already see the road block with electric bike and the costs involved. I really think you are going to be limited to the range you can(want to) afford or you have to pay the piper for the good batteries.

Contact board member Frank. He has built more than one successful electric motorcycle. I have a feeling he will tell you that if you want the level of performance you described, you'll need a Lithium battery.

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If it surges, that's normal, upshift.

I took a good look at this more than once. If you want the thing to go you need juice and lots of it. That means with lead acid batteries you will need 5 or 6. That is a big load for a small frame so the frame choice has to be larger and the whole thing is starting to get pretty heavy. If you go for new battery technologies, the battery price goes up by a factor of 3 or 4 but the weight gets cut in half.

I think it would still be fun to build but after a lot of study I had a budget of about $5K for motor, controller and batteries. Doing this kind of design tends to make you appreciate the energy density of gasoline. There is a tremendous amount of energy in a gallon of gas and it is hard to match with batteries.

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Rotortech
Indianapolis
1974 S3

I worked with a guy once who said an electric car is like a gasoline car with a one gallon gas tank that takes eight hours to fill. And he's a proponent of electric cars!

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If it surges, that's normal, upshift.

Provided my math is right(which is always questionable because math and I don't get along) for a 48V 40Ah pack using these Lipos, I'd need 12 2S(7.4V nominal voltage) packs, which would put me at about $1500. The Nano-techs are pretty good cells and the price is not terrible, but I don't like that Lipos need a special charger(and there's the whole bursting into flames if damaged or overcharged thing...) At 500g/pack, that also gives me a battery weight of only 14lbs. Somebody check my math, that doesn't sound right
http://www.hobbyking.com/hobbyking/stor ... ible_.html

Bumping it up to 50Ah adds $240, and 2.2 lbs.

It looks like each one has a 10 A-h capacity at 7.4 volts. For 48V 10 A-h, you'd need 7 of them. For 40 A-h you'll need 28 of them. 48V x 40 A-h = 1920 Watt hours. That's not much more than 2 hp-hours, meaning if the speed you're going requires 2 hp to maintain, the battery will be completely discharged in 1 hour. I doubt you'll go 60 mph with 2 hp. You definitely need to get Frank's advice.

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If it surges, that's normal, upshift.

As Jim said, you want to get those Amp-hours up more. 48 cells is probably a good starting point. That pack would be a little over 50 lb and you would have to drive like an old lady.

Or you can buy this: http://www.brammo.com/store/empulse

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Rotortech
Indianapolis
1974 S3

I am right with you Jeff I have been looking and calculating the cost on an electric drag bike. It really makes sense on a drag bike becouse of the duration but the peak amperage draw and the amount of volts needed ( I was trying to calculate about 80 HP ) is do able but expensive. I have not given up the idea but I will continue to work with airplanes for now. I will be building a competition aerobatic plane using about 3000 watts of power. My drag bike calculations come out to about 80,000 watts or so. Keep us posted !

I knew my math had to be off...