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Old 04-02-2009, 04:45 PM   #5 (permalink)
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Originally Posted by Wonderboy View Post
I've found more motors:
I went to a local junkyard and opened a junked forklift to find 2 motors:

a GE 2.3HP 91 amp 24V 2400RPM
and an Advanced DC Motors 24V. The only other useful markings on this one was a box labeled "rating", which said "AU2500 9-4-94"

Is the only reason higher voltage is more pervasive in EVs is that they typically yield greater speed and power, and that 24V would be fine if it ever does provide enough torque/speed?

What are the pros/cons of using a lower (24v) voltage motor in EVs, but more specifically electric motorcycles. Is there an RPM range to look for? Is there an amperage range to look for?

If one or both of these motors I found (they might not work, but I doubt that and could bring some batteries to test them out - that's all I have to do, right? just batteries and jumper cables?) could propel a cycle to 45 as opposed to 55, I'd definitely be willing to compromise, because that junkyard's prices are extremely reasonable. Price will be king over my speed desires.

I'd be pretty excited if one of these motors were suitable.
To test bring a 12v car battery and 2 sets of jumper cables (how you wire depends on wether shunt would or series)

Hmm better make sure the motors have 4 terminals AKA series wound, shunt wound non reversables can be tough to get cheap controller for.

They probably are both suitable, 2.5hp may not sound like much but you can get much more peak power than that from the motor anyway (especially if you up voltage). ALso having a motor repaired or rewound isn't always the end of the world, there are several local places that do it quite reasonably (actually downright cheap)

As for why you would want more than 24 volt the answer is simple 2400rpm, figure it out and you need lots of gearing to get speed and that gearing will likely cause more amp draw than you would want should you gear up. Higher voltage = higher top rpm, better acceleration, lower amp draw.

HOWEVER, my comutacar was originally 12v/24v/48v powered and would go about 22mph @ 24 volts. My car weighed roughly 1200lbs, so a motorcycle would likely go just fine at 24volts but I would not expect speeds beyond 45mph as you likely don't have enough gears and you would need to verify your amp draw as you up shift.

Next as to why you would want a lower voltage the answer is again simple, the lower the voltage the fewer batteries and thus larger amphour/ better reliability along with lower costs on the battery front. Also lower voltages have lower costs all the way around, cheaper charger, cheaper controller, less wiring, cheaper dc-dc.

My recommendation would be to start simple with a controller & charger solution that will allow you to up the voltage later.

That way if you can complete the important machining aspects of the conversion then the more simplistic battery voltage aspects can be played with later.

You will however have to base how cheap you go on what expectations you have, if you just want it to move and don't care about top speed or accelleration get a golfcart 24v-48v controller cheap, use car battery chargers to start and test it out to see if its acceptable, you can always upgrade as you go. I do however believe that you will probably want at least 36 volts but you can test you may find 24volts is just fine for in town commuting.

Also something I think is workable is to use simple contactor controls on a motorcycle, since you likely have 6 gears you could have 6 or 12 speeds without a speed controller. And your acceleration would be jaw dropping to say the least.

Good Luck

Last edited by rmay635703; 04-02-2009 at 04:51 PM..
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