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[HotRodHoose]

I am a senior at Penn State University, getting my Bachelor's in Mechanical Engineering, after my first Bachelor's I am heading for a degree in Electrical Engineering.  As a senior project I am designing and building an EV Motorcycle.  I have to plan this semester and build over the summer and next semester.  I need some advice, I am shooting for about a 25 mile range, with a top speed of about 75mph, I was thinking of doing two 48 volt permanent magnet DC motors, running them in series and then switch them to parallel after a certain speed.  I was thinking of running 8 odyssey lead acid batteries.  I dont know what calculations to use to figure out if 96 volts will work or if there is a better way to do it.  I want power with a decent range.  I am building this to go back and forth to work which is 23.55 miles from home and I will be on a 65MPH highway.  Thanks for any advice!

[skadamo]

Welcome!  Sounds like a great project.  Hopefully someone who knows can give you some good advice. 

[Bogan]

motorwise, the etek-rt is probly your best bet, its a brushed dc which should have plenty of power for 75mph (depending on bike shape though). two 48 volt motors would probably just increase the cost, and complexity of the project. If you run lead acid batteries make sure they can output large currents for extended periods of time, and go for deep cycle ones, otherwise the Ahr rating is completely unattainable.

[HotRodHoose]

The etek motors were the ones i was looking at.  If i use just one motor, what voltage should i run, if i run motors i would have good low end power along with good top end as well.  I was actually told to steer clear from deep cycle batteries and go for more of the absorbed glass mat Lead acid Odyssey batteries.  I have found lots of lead acid batteries, where can i look for NiMH or Lithium batteries?  I am not too concerned with price right now, i am in the design phase, so i have to design the best one and then make changes to fit my budget, its kind of a requirement of the class.  One question i had was, do you buy a charger to charge all of the batteries at once with your total voltage, or do you charge each single battery?  Thanks

[Bogan]

the etek-rt is rated to 72v, so if you can fit enough batteries in that would give the best acceleration. If you really wan good acceleration you would probly be better off puting in a small gearbox rather than a second motor, though i think just gear it right and it will have adequate acceleration. Yeh AGM is a type of deep cycle battery (i will be running this sort in a few months), though with agm you got to make sure the batteries can supply enough current. I think there are ev places that sell some lithium phosphate batteries though they are quite expensive, some second hand nimh hybrid batteries are probly your best bet if you can track them down. Lead acid batteries you can charge all at once, but i dont think you can do this if you run lithium or nimh batteries.

Any idea on what sort of donor bike you will be using?

[HotRodHoose]

I actually work at a motorcycle dealership, so I am building a bike, i am going to find a frame and then make a lot of the bike myself.  What kind of calculations can I do to figure out if I can achieve my range and MPH?  I think I was told to stay away form marine deep cycle, not deep cycle in general.  Is there any websites that I can look around on and check everything out?

[Bogan]

Yeh that sound about right, marine deep cycle are flooded i think, so not nearly as good as agm.
Range and mph is almost completely dependant on your aerodynamics, im using asportsbike donor (1990 KR1) so i found the areo factor of a R1 i think, then based my calculations around that. Though early testing was indicating it uses significantly more power than i thought, which could be due to brake drag.
MPH i would just use the motor hp, and compare that to existing bikes of similar shape.

[Bogan]

for example, a GN125 has 12hp and does 75mph for long periods of time. Aerodymically it is a horrible bike, so with a Etek-rt (9hp continuous, 18 peak) and a bike with a fairing i would expect it to easily do 75mph

[HotRodHoose]

Ok, but i thought to figure out distance you can use some equations using the amp hours of your battery capabilities and such to find out if it is even possible to reach 25 miles or not.  I just dont know what you use, i know you have to convert to power since its like 746 watts equals a horsepower, and then in general about 6 HP to cruise at 75 MPH, but do you use the batteries power, motor power, or do you do something with the controller?

[Bogan]

Yip, that pretty easy to work out, though it does relie on the assumption of power required to do 75mph.

first work out the watt hours of your batteries, amp hours(per battery) * voltage (per battery) * number of batteries.
Multiply the watt hours by the battery efficiency, which varie from type to type, but 0.8 is probably a good approximate value.

Find the motors power consumption, @e stimated 75mph 6hp*746
gives 4476

Divide the total watt hours by the motors power consumtion to find out how many hours it will run for, then multiply the hours by the speed to get distance.
example with my battery pack
watt hours = 35*12*3*0.8=1008
1008/4476=0.2252hrs
0.2252*75=16.9 miles

hope thats what you were after

[HotRodHoose]

Heck yeah, thanks a lot.  Sorry I haven't been on here for a while, my every day driver blew a head gasket that i just figured out after a week of diagnostic work,    If anyone knows where I can look for NiMH batteries that would be great, thanks a lot!   Thank you very much Bogan for all of the help, you are awesome!

[HotRodHoose]

Bogan, is that a pretty good estimation compared to what you are really getting?  Are you really only running 3 batteries at 36 volts?

[Bogan]

alas, i have not yet completed the controller circuit so i cannot compare with what im actually getting, however using a speed controller from an electric bicycle, and wiring too small, i was almost double the expected current at 40kmhr, although i expect a large part of this extra power needed is due to the sub-standard speed controller and wiring, as well as some brake drag.
Yeh for testing ill only be running 3* 12v SLA, as ill be able to do 50kmhr (speed limit around town anyway), and if testing goes well, ill try and get some more fancy batteries, im designing the controller so they will bolt straight in without any electircal changes.

[HotRodHoose]

Thats good, what controllers do you think are the best to use, I was told to try to get a curtis controller.  But then someone else gave me this site where you can design your own controller, but I dont know how good it is: pwmpower.com.  Thanks

[Bogan]

probably a purpose built EV controller would be best, i havent had any experiene with these, so cant help you with brand names. Though id expect you get what you pay for,, and also depends what features you are after, current/battery monitoring, regen braking etc