Hello
I'm planning a conversion of a Kawasaki 400 into an electric commuter bike.
I have about a 20 mile round trip and MAYBE permission to re-charge while at work.
If possible, I'd like the ability to make 55 MPH for a portion of that trip, in order to use freeway to avoid downtown; otherwise 30-40 mph will be normal speeds.
As I'm researching the possible components and configurations available I think I'd like to use the MARS motor (similar to Etak) with a Sevcon controller.
What I'd like some feedback on is what I'll call the Voltage-versus-Amp Hours question.
I realize the final gear ratio determines your bike's performance, but how best to decide the battery choices when you're talking 24 or more volts and 50 to 120 Amp Hour ranges per battery?
What are the trade offs of having say: 24 volts and 200 amp hours for your battery pack versus 48 volts with 200 amp hours? Or put another way: 2 Big ones versus 4 smaller ones?
thanks
HOPOIL
(disclaimer: I haven't built anything yet)
Your load in Watts (or HP, 750W being One-HP) can be accomplished with a fat high-amp/low-volt motor, or a high-volt smaller motor.
Its better to over-volt (48/60-volts into a 36-volt motor) than to under volt (48 volts into a 90 volt motor)...Don't know why, but it's a more than 2:1 ratio, big difference.
If its really important for you to be able to occasionally travel at freeway speeds, you may want to adapt a motor onto the existing transmission/clutch. bearing in mind that only two of the gears will be useful, creating a high range/low range.
If you're willing to limit yourself to 45 MPH, it will save you trouble, money, and range.
More voltage will provide higher RPM's, but adding a 500-tooth sprocket will NOT allow a bicycle to travel 100 MPH.
If 60/72/84-volts will provide the rpms/power you need, when you want more range you will run into a battery volume problem. If you have five small 12V batteries to get 60 volts and you want more range, you can add a second string of 5 additional small batteries in parallel, or change the 5 smalls for 5 large.
If you want more top speed and more range at the same time, the only available option today is the very expensive LiFePO4 Lithiums.
Start a file with the links to EV motorcycles. list the motor, controller, sprocket tooth-count, battery voltage and type, top speed, and range.
Don't try to re-invent the wheel, whatever you can imagine, someone has tried already. Copy someone who is happy.
I agree with most everything spinningmagnets says above. I'm building a CB-750 into an EV and I've gone with 84V (I also went with honking great 75Ah batteries so the thing will look like a tank when finished ;-) )
In general I think you'll want at least 72V. A good place to start is John Bidwell's book "Secrets of El-Ninja"
I don't think I've seen anyone mate a motor to an existing transmission for a motorbike yet (it's common with cars though). The trouble is they're an integrated unit. So, you're pretty much stuck with a single gear set up. Pick a top speed and work backwards from there. Check out my blog if you want to see how I've approached it.
But beware: I haven't completed my project and there's still plenty of time for me to FUBAR...
http://visforvoltage.org/blog/jdh2550-1
John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.
Here's one that should get an easy yes or no answer.
Can you mix and match batteries???
if you get a super deal on a 12v 100Ah AGM sealed battery, can you add three other different (12v 50 Ah) batteries to get a 48 Volt pack???
No.
<table border="0" style="border:1px solid #999999; padding:10px;"><tr><td>
<a href="http://www.BaseStationZero.com">[img]http://visforvoltage.org/files/u419...
[size=1][color=black]www.[/color][color=#337799]BaseStationZero[/color][co
I agree, the easy answer is NO.
However, the more complex answer is yes it's possible. Now, I know usatracy has already pointed that out. However, I'm not sure I agree that one would be crazy to do it. I know I've come across at least one project over on EV Album that successfully used different batteries with different capacities and different chemistries. The big advantage is cost - they scrounged old batteries from a number of different places and successfully re-conditioned them and used them for an EV pickup project. These guys were battery experts with a lifetime of experience - you'd certainly want to rely on their knowledge not attempt to do this from scratch yourself.
But, in your situation it's probably best to stick with the easy answer. ;-)
John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.
Yes. But, there's usually no logic in doing that for a series "string" of batteries. This is because the usable capacity will be that of the lowest capacity battery in the string. The battery that is 100 ah will only have 50 ah usable capacity when put in a string with other 50 ah batteries, and the remaining 50 ah will just be dead weight. If you keep limping along after the other batteries are dead then they will be reversed charged and killed very quickly by the charge in the 100 ah battery.
Sometimes there's a good reason for doing this. You can take a smaller capacity battery and momentarily switch it in series with the main battery pack to up the voltage, and provide a temporary boost in power. But if it remains in the circuit, than it will be discharged and reverse charged before the other batteries are discharged.
However, you can put different capacity batteries that are the same voltage in parallel.
[url=/forum-topic/motorcycles-and-large-scooters/587-my-kz750-electric-motorcycle-project]KZ750 Motorcycle Conversion[/url]
[url=/forum-topic/motorcycles-and-large-scooters/588-fixing-my-chinese-scooter]900 watt scooter[/url]
Pic from http://www.electri