Electric Ninja 250 Cafe

JPanichella

Been Around the Block
I'm building another electric bike, except this time I promise to finish it. Some of you guys might remember a few years ago when I was working on an electric CB750, but unfortunately I had to sell that project to fund a move to California. Now I've got a job and some time, and things have changed a little bit in battery tech to make this project a bit more affordable.

I bought a titled Ninja 250 with a blown motor (somebody took it on the freeway without any oil in it) last weekend and stripped it down. I decided to get a ninja 250 mostly because it was dirt cheap, good enough brakes and suspension, and uses the engine as a stressed frame member, leaving plenty of room for the batteries and electric drive system. I want to keep the entire high voltage system (batteries, motor, controller, main disconnect, battery management system, etc.) as one big "module" that will bolt in place of the engine. The tank will have the underside cut out to conceal the battery charger, and DC DC Converter (reduces the pack voltage of 72V nominal to 12V for lights/horn/etc.) and any stuff I need for the 12V system.

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There's a place in vegas that sells NOS Nissan Leaf batteries for a great price. Up until recently, home made electric motorcycles either carted around big lead acid batteries, or big chunky prismatic lithium cells (the ones I was using for my first build). No other form or lithium was practical, you could either try to assemble large, complex battery packs from 18650 cells, which is what Tesla does. Or you could try to work with a bunch of hobby RC lithium polymer packs, but the cycle life was shitty (like 400 full cycles), the quality control was terrible, and they liked to catch fire if not treated well. These Nissan leaf cells are safe, easy to package and connect, and fairly energy dense, especially for the price.

My batteries arrived today, they're a bit smaller than I expected and should fit great. These are only 4 of them, but there will be a total of ten, packaged in two stacks like this:

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Went into CAD and mocked up a relatively close frame to show what I'm thinking so far.

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My expectations are:

80 MPH top speed
40-50 mile range (50 is probably optimistic)
Motor is capable of 35 or 40 peak HP
Under $4K

This will be mostly for commuting in city traffic, but should be a fun little lanesplitter. If you have any specific questions let me know.
 
Sick! I've always been a fan of electric conversions; my uncle has an electric Porsche 914 that he drives around town. My electrical knowledge is extremely limited, but your Ninja seems like a good candidate and I look forward to following along.
 
Awesome. I built an electric concept hot rod roadster a few years back. Been into one-off electric vehicles ever since. Very cool. Cant wait to see the progress.
 
EXCELLENT! Always wanted to see that 750 done. Watching this one with keen interest!
 
Love it, owning both a pre-gen and a new gen, I'm watching intently. Having electric torque will be awesome
 
Cool. Try to hook up a transmission that will help big time for speed and battery charge and perhaps look in to deceleration recharging. As well as put coils on the forks and magnets on the rims, small recharge. Every bit helps
 
Ubergeez said:
Cool. Try to hook up a transmission that will help big time for speed and battery charge and perhaps look in to deceleration recharging. As well as put coils on the forks and magnets on the rims, small recharge. Every bit helps

Thanks everybody for the encouraging words.

There's been lots of debate about the usability of transmissions in electric vehicles. While they do help keep the motor in it's range of peak efficiency, this is much more important on internal combustion engines due to the much narrower torque band. I personally feel they're not worth the extra weight and space, it's more beneficial to use that space for extra batteries and a higher powered motor and controller.

Unfortunately the controller I plan on using doesn't have regenerative braking. I'd have to go with a more complicated, Chinese made controller that has a worse reputation when it comes to reliability. Another reason I chose a bike with disc brakes in front and back. I'll rebuild them with stainless lines to make sure they have plenty of stopping power.

I'm intending on leaving this bike naked, I'm trying to make it as light as possible.
 
Assembled the pack today, to take measurements for the battery box. Measures about 18" X 7.25" X 12.25". Ground clearance shouldn't be an issue.

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First attempt at a wiring diagram, I'm having the smart people over at the electric motorcycle forum make sure I'm not going to electrocute myself.

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JPanichella said:
First attempt at a wiring diagram, I'm having the smart people over at the electric motorcycle forum make sure I'm not going to electrocute myself.

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....good call....
 
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