# EV bike help



## Little Rhody (Jun 17, 2008)

Lots of reading is the first thing you can do. There is lots of info outthere to answer most of your questions. 

Start here: http://www.diyelectriccar.com/forums/showthread.php/ev-information-669.html

Also look at other build from others. Here is a good site with a few good examples.
http://www.evalbum.com/type/MTCY

Oh, ya....... Make sure you have a enough funds, Your request will cost a bit. 

As for building a scratch built machine, I hope you are an accomplished fabricator (as I am) otherwise you tool expense and trial and error will suck up your budget real fast. A conversion is the fastest way to an ev build IMO. 

Lr


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## zemon1 (Aug 5, 2008)

my dad is a heavy desiel mechanic and ive bee able to weld and what not since i was 7, were probly good on that front, however i was thinking carbon fiber XD

Thanks for the reading, ill look in to those.


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## akumabito (Jun 23, 2008)

zemon1 said:


> i would like to make an EV bike, but i have no idea how to attack it.
> 
> I want a top speed around 100 or so
> I want to make my own frame and every thing, or ill use a GSX600, or ZZR600.
> ...


Whew, those are some big numbers there! I don't think I've seen an electric bike with a 75 mile range yet. (but maybe I just haven't been looking hard enough)

*DISCLAIMER: I am new at this as well, so the following figures could very well be completely FUBAR and utterly useless. I'm sure someone will step in to correct me though *

I'm guesstimating your bike would need about 50 or 60 Hp or so to run at 100MPH, so that would translate to roughly 37.5kW to 45kW.

Let's say you'd be running 20kW at a 50Mph cruise speed, you'd need to run for an hour and a half to get your range, meaning your battery pack will need to be able to supply at least 30kW + a reserve to account for inefficiencies, drivetrain losses, and battery safety. Someone advised me recently to go with a 50% safety margin, but that could be different for LiOn batteries.. Anyhow.. a 60kW battery pack can run pretty big. At 72V, you'd be looking at 833 Amp/hr..

I don't know if you looked at batteries yet, but assuming they are 12V, you'll need 6 of 'm just to get your 72V, then divide 833 amp/hr by whatever the capacity of your batteries are to see how many packs of 6 you'd need.

For example, assuming each battery could deliver 12V and 50 Amp/hr, you'd need 6 of those to get to 72 V, and then 833/50=16.66 (you'll probably get away with 16) of those packs - or a total of 16x6=96 batteries.

Now assuming I'm not talking out of my ass... how big are those batteries, how heavy are they and how would they fit in/on a bike frame?

I'm just hoping I screwed up the numbers somewhere as I can't really picture 96 batteries draped around a motorcycle..


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## zemon1 (Aug 5, 2008)

Holy shit, looks like i was aiming a little high lol, after you started putting letters and numbers together my brain gave up lmao

i really want big range but going down to 75 MPH tops wouldnt be that bad...

i read some of those pages posted, spent like an hour and my head just said hmmm ok, i quit lol. cant remember a thing i read...


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## zemon1 (Aug 5, 2008)

akumabito said:


> I'm guesstimating your bike would need about 50 or 60 Hp or so to run at 100MPH, so that would translate to roughly 37.5kW to 45kW.
> 
> Let's say you'd be running 20kW at a 50Mph cruise speed, you'd need to run for an hour and a half to get your range, meaning your battery pack will need to be able to supply at least 30kW + a reserve to account for inefficiencies, drivetrain losses, and battery safety. Someone advised me recently to go with a 50% safety margin, but that could be different for LiOn batteries.. Anyhow.. a 60kW battery pack can run pretty big. At 72V, you'd be looking at 833 Amp/hr..
> 
> ...


Can you please explain this to me, i hate being a pain in the ass but WHAT! lol


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## akumabito (Jun 23, 2008)

Yeah, it gets a bit daunting if you're not accustomed with it. I have the exact same thing myself.. the first time I did some EV calculations for a project I had in mind, I could not believe the numbers i was getting.. 

I suppose the ideal solution is to figure out how much power/range you _really_ need. if the bike is meant as a commuter, what is the round-trip distance? Add a small safety margin to that, and use that as the basis. Most people are quite satisfied with a 30 to 40 mile range. 

What top speed do you really need? Unless you're in an area without speed limits, my guess is you really don't need a top speed of more than 60mph. If your commute doesn't include highways, you can drop that to 50Mph or so. 

Figure out how much power you actually need - estimate the final weight of the bike + rider, look up the drag coefficient and tire rollign resistance, then use this formula to figure out how much you'd _actually_ need.




> Power in Watts = ((





> Mass in kg) (9.8m/s²) (Velocity in m/s) (Rolling Resistance)) + ((0.6465) (Coefficient of Drag) (Area in m²) (Velocity^3))




Then use these numbers to size the battery pack to something that could more easily be incorporated into a bike frame. It also doesn't hurt to see what others have done, and what sort of performance they are getting. There are a number of nice buildups posted on this forum.


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## zemon1 (Aug 5, 2008)

ok, how/where do i look up the drag coefficient and tire rollign resistance.
and i cant uderstand this thing lol. im sorry im such a pain in the ass.


Quote:
Power in Watts = (( 
Quote:
Mass in kg) (9.8m/s²) (Velocity in m/s) (Rolling Resistance)) + ((0.6465) (Coefficient of Drag) (Area in m²) (Velocity^3))


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## zemon1 (Aug 5, 2008)

what do you guys think of these products? 
http://www.thunder-sky.com/products_en.asp?fid=66&fid2=70
i dont like buying something with chinese/japanese writing next to it but if its cheap and good, how much lead based paint could be in it.? lol!
counldnt help that one lol, but seriously what do you think about these?


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## Little Rhody (Jun 17, 2008)

zemon1 said:


> what do you guys think of these products?
> http://www.thunder-sky.com/products_en.asp?fid=66&fid2=70
> i dont like buying something with chinese/japanese writing next to it but if its cheap and good, how much lead based paint could be in it.? lol!
> counldnt help that one lol, but seriously what do you think about these?


I Like these batts, and had them on order. But my supplier did a bait and switch with me. The biggest problems with them is 1)- getting them, and 2)- the discharge rate. 

I have some that are near identical in specs, from another manufacturer. Im interested in testing them. There a few bikes out there running them and seem to be getting good results. 

LR


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## xrotaryguy (Jul 26, 2007)

If you have trouble with the calculations, just look at some of the bikes on the EV album. You can see what components they used and what performance they attained and work from there.


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## joseph3354 (Apr 2, 2008)

killacycle is running 2 6.7 inch motors at high voltage to run 160mph in the quarter mile. your project is not likely to need that much power.what you want as far as speed is concerned is achievable.range is a different story.my best guess ( i'm no expert) is maybe 120v pack 130 amp hours or maybe 160v 100 amp hours.check out the evalbum.com site and see what others are doing. good luck! 

xrotaryguy posted while i was typing,lol.


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## zemon1 (Aug 5, 2008)

yeah i found a guy on there willing to help me, he has i bike that does a little less than what i want.
Thanks for all the help you guys have been giving me. When i know something, i learn about it like fire but the closest i come to electronics is computers and ill i can do is build them and but i just buy parts and put them on i dont modify lol


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## zemon1 (Aug 5, 2008)

anyone have some links on motors i could use to achive my target speed?


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## frodus (Apr 12, 2008)

yes, AC, electricmotorsport.com has a couple systems.

plan on spending over 3 grand.

100mph is a tall order unless you want to keep the transmission. Even with a series wound motor, you'll either have high top speed and bad acceleration, or great acceleration and low top speed. You either need AC so you can make the motor go higher RPM's or figure out a multiple gear transmission.

75 miles is going to be expensive, plan on spending over 5 grand on batteries alone.

try looking on evalbum more for some ideas... ranges typically don't go over 50 miles, and top speeds of 60-70mph.


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## zemon1 (Aug 5, 2008)

i planned on the 5 for batteries, but there are no other systems that can go 0-65 fast and then just chill there lol

sorry if i offened you on that other post, i had some rl issuses there lol

someone has already told me this but what is the avg wh/mile for bike? nvm i already know i need 10kw


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## frodus (Apr 12, 2008)

zemon1 said:


> i planned on the 5 for batteries, but there are no other systems that can go 0-65 fast and then just chill there lol
> 
> sorry if i offened you on that other post, i had some rl issuses there lol
> 
> someone has already told me this but what is the avg wh/mile for bike? nvm i already know i need 10kw


we're all tryin to help

Average w/h per mile is around 100-125 for a motorcycle from what others have done. I don't have gauges yet, but I will soon so keep updated.

All things are possible, but, unfortunately, its going to cost.


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## zemon1 (Aug 5, 2008)

im trying to make this thing cheap but good since i want to sell them. after i get some capitol and profiet i could certianly get parts cheaper do to the wholesale quanities. 

I was thinking of putting a sign in my front yard that says: Gas prices getting you down? How would you like a motorcycle that gets 244MPG???!!! How about a car that gets 120MPG???!!! just call 555-2918 for details

hoping to sell car for 60-80k and bike for 15-20k 
the car i think would cost 45-50k to make and the bike 7.5-10k

what are the pros and cons for ac motors and dc motors. i hear ac is more efficient, but is it worth it?


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