Motenergy 4201 and Cabin Motorcycle

[alex12342011]

So I have acquired a motenergy 4201 and a 24FET 10KW controller modified with beefy traces and wiring.

Originally my intentions were to build an ebike, but now I want to build something along the lines of this:


The vehicle would be 400lbs max without riders, and would have a very low drag coefficient under 0.2

I am aiming for a top speed of 60mph, and the 0-60mph time should be no less than 14 seconds. My intention is to make a street legal vehicle which could go on the freeway.

At speed, the horsepower required to overcome drag from rolling and wind resistance would definitely be attainable with the 4201s 8hp continuous rating. I am just concerned with the acceleration, if it takes 30 seconds to get to 60mph, that is not very safe or practical on the road. I am wondering if I could overspec the motor for acceleration, possibly to put out 20-30hp instead of the rated 15hp peak just for accelerating up to speed.

Is this a possible project, or am I crazy?

 

[amberwolf]

How fast can you cool the internals of the motor? Faster than the excess heat buildup so it doesn't cook?

That's the main thing that limits the peak (and continuous) power a motor could produce.

During the initial parts of acceleration from a stop is the worst part of that, but if you end up running it at it's top continous power rating after overheating it from over-peaking the power during acceleration, then if they didnt' rate the motor conservatively, but rather optimistically, you run the risk of damaging it if you can't cool it at least as fast as you heat it.

 

[alex12342011]

Ah I see, so some sort of temperature sensor and a blower could suffice. I might just go with a single seat to reduce the weight to improve acceleration.

 

[alex12342011]

Actually, has anyone ever watercooled such a motor? Or a similar type of motor? I know doc bass watercooled a hub motor, but that is a bit different.

 

[neptronix]

Golden motor's 72v winding of their 5-10kw motor shows 9kW continuous at 88% efficiency on their dyno graph. That's 10.7hp. Might move your vehicle around pretty well. It can come with a watercooling option.

Your 24FET controller is probably not going to be strong enough to push the needed current for too long though. I think those controllers are good for about 80A continuous on 4110's.
You'll really want a 36FET to push the motor fully. Greentime has some for sale that are rated for 100-120A.

If you go brushed, the ME1003 would rock. 14,400 kW continuous on 72v, ~90% efficiency. 19HP continuous.. that would move pretty well :]

 

[alex12342011]

So, this controller with the upgraded battery/phase wires would only be capable of 80A continuous? I thought it would at least be able to do 100A continuous.

Its nice that controllers are easily swapped, so I may just get a 36FET later. I am also thinking it would have to be a single seater for lightweight, maybe by modifying a cbr125 to feet forward. This is all speculation right now, and I have to wait until I get a break from school to do some serious consideration.

 

[alex12342011]

Edited thread title to "cabin" motorcycle .

 

[neptronix]

So, this controller with the upgraded battery/phase wires would only be capable of 80A continuous? I thought it would at least be able to do 100A continuous.

Oh - that's a different story. That thing is upgraded. I was talking about a stock unit. I completely skipped over the fact that you were talking about the one i sold you. :lol:

To be honest, i am not aware of what those are rated at on a continuous power basis. A stock 12FET infineon is often rated for 40A battery. So i'd assume that this 24FET sans upgrades could push 80A continuous. Maybe it'll do 90A continuous due to much lower resistance in all areas where power is transmitted.

On a heavy vehicle like what you're talking about, these controllers which are designed for scooters and bikes can be really stressed. You will probably be pushing continuous power almost non-stop with that 24FET. That's not good because you won't have margin for the controller to cool off.

So for that motor - if you want to push it to what it's capable in such a heavy vehicle, you really want a 36FET or higher, so that you can push around 130A-150A battery, 100A constant.

A 24FET + motenergy 4201 on a *bike* is pants soilingly fast, but that controller will never get the motor warm, if at all on a bike. You could roll along at ~50mph on a setup like that because the cruising and hill climbing power will be so much lower. Not so much with a 500lb vehicle like you're talking about.

 

[neptronix]

http://www.aliexpress.com/store/pro...shless-speed-controller/313864_578300665.html

P.S. if you are okay with a nonprogrammable controller, here's the greentime 36FET.

You could finally get that motor warm with one of these :lol:

 

[John in CR]

Things would be so much easier if you hack a bunch of that weight off. Even if you say 50lbs each for the front and rear wheel with suspension and brakes, plus 100lb for motor and battery, then before considering some serious savings in that 200lbs, there's gotta be a way to lop off at least 100lbs of the remaining 200.

Assuming you aren't large like me, then get the vehicle down to 200lbs, so your all up weight without a passenger is below 400lbs, then 70mph AND exhilarating acceleration become easy.

Regarding the controller, with something that aerodynamic, why are you talking about 100A continuous? Unless you have a mountain to climb or a load that is too heavy, then your focus needs to be on peak, not continuous. That's because peak will occur only in the first few seconds of acceleration. Then your motor gets into its prime efficiency band and the controller goes from current limiting to full duty or duty determined by throttle position, at which point your system is cruising easy under little stress. If any part (motor, controller, or battery) are anywhere close to stress at continuous running then failure is all but guaranteed, and peak vs continuous probably needs to be something like a 3:1 relationship unless your goal is extreme speed. 300A peak is asking too much from that controller. 100A continuous, well it would depend on the motor and the throttle position, so maybe.

John

 

[Arlo1]

So, this controller with the upgraded battery/phase wires would only be capable of 80A continuous? I thought it would at least be able to do 100A continuous.

Its nice that controllers are easily swapped, so I may just get a 36FET later. I am also thinking it would have to be a single seater for lightweight, maybe by modifying a cbr125 to feet forward. This is all speculation right now, and I have to wait until I get a break from school to do some serious consideration.

Depends on what it looks like inside. And If you can get some cooling on it. I have seen >260 amps for a few seconds at a time on my 24 fet and it was only a few seconds because I was at top speed that fast. A 24 fet is over kill for most hub motors (mines a x5). I think the 24 fet might be ok for your aplication if set up properly.

 

[Dauntless]

. . . . but now I want to build something along the lines of this:

Is this a possible project, or am I crazy?

There's one huge question: When you stop at the light/stopsign/etc., what holds the bike up?

 

[amberwolf]

On the one in the picture, those little wheels in the recessed area pop out below a certain speed, IIRC.

 

[jana]

Really cool project, I wish you good luck!