KHB - Suzuki skydrive 125 electric conversion

[kreal]

So I've decided to convert an old Suzuki skydrive 125 to 3000w electric. The project is completed now! and this thread can be used for inspiration for others.

I've tried to use the original CVT drive, but this was awful, so I ended up using chain for direct drive, this also give me regenerative breaking.

The motor is qsmotor 3000w 13870h version 3.0 with the controller being VOTOL-EM150SP






However I still need to find better batteries. Right now I am using 6x 12v SLA 5Ah for a total of 72v, but 5Ah is way to little, I need at least 20Ah, but the thing is, I don't know where to put them









I now have 14T in front and 45T in back using 428d chain, and the torque is amazing, while the top speed being 90km/t

 

[kreal]

In the lack of space for batteries, I was thinking to cut open the original muffler exhaust, and placing the batteries in there?

12v lead acid for the time being.

What do you think?

 

[John in CR]

Battery placement is the biggest problem with conversions, and why I use only some of the original frame in my builds. In your case, simply give up the step thru part and fill the center with batteries leaving only the portion of the platform you actually use for your feet left and right intact.

While it will require some mods to the bodywork, I would add something like a top tube on a bicycle. That would greatly improve the strength of the frame...enough that you could even cut out some of the weight at the bottom of the original frame and still have a stronger frame than the original with less weight.

 

[Balmorhea]

I’m not surprised that direct drive is better than CVT in your application, but I am curious what was so awful about CVT?

 

[kreal]

Battery placement is the biggest problem with conversions, and why I use only some of the original frame in my builds. In your case, simply give up the step thru part and fill the center with batteries leaving only the portion of the platform you actually use for your feet left and right intact.

While it will require some mods to the bodywork, I would add something like a top tube on a bicycle. That would greatly improve the strength of the frame...enough that you could even cut out some of the weight at the bottom of the original frame and still have a stronger frame than the original with less weight.

Thanks, yeah the issue is I'm using mid-mount motor instead of hub motor. So missing some space because of this.

 

[kreal]

I’m not surprised that direct drive is better than CVT in your application, but I am curious what was so awful about CVT?

The motors RPM was not good enough in my opinion. I had to use field weakening for any descend speed.

 

[John in CR]

I’m not surprised that direct drive is better than CVT in your application, but I am curious what was so awful about CVT?

If you're interested in trying CVT's with electric motors, then check with forum member Gwhy. He used the combination of RC outrunner motors with scooter CVT's on multiple builds. I think it's simply a matter of matching rpms with the original motor. I certainly wouldn't ever go that route though, because performance is so much better simply using a slightly bigger motor with a fixed gearing. The only time variable gearing is needed with electrics is when you essentially have a dual use situation where you require high speed on flat terrain along with low speeds under high loads like hauling big loads up long steep hills. For those requirements a 2 speed with the correct gearing will always suffice unless you have tremendous variance in load requiring a 3rd gear.

While field weakening can be used to extend the top speed of a fixed gearing, no electronic trickery such as Delta/WYE or Series/Parallel switching can ever help exceed the performance of a simple single speed. Nor can they help meet a true dual use requirement.

 

[John in CR]

Battery placement is the biggest problem with conversions, and why I use only some of the original frame in my builds. In your case, simply give up the step thru part and fill the center with batteries leaving only the portion of the platform you actually use for your feet left and right intact.

While it will require some mods to the bodywork, I would add something like a top tube on a bicycle. That would greatly improve the strength of the frame...enough that you could even cut out some of the weight at the bottom of the original frame and still have a stronger frame than the original with less weight.

Thanks, yeah the issue is I'm using mid-mount motor instead of hub motor. So missing some space because of this.

Even with a hubmotor those kinds of scoots don't have much room for batteries. What I'm talking about is modifying the look toward something like the Derbi's that Scottydog uses for his escooters. That unused space along the center line offers lots of room for batteries. Check out his thread here https://endless-sphere.com/forums/viewtopic.php?f=12&t=59873.

 

[kreal]

Battery placement is the biggest problem with conversions, and why I use only some of the original frame in my builds. In your case, simply give up the step thru part and fill the center with batteries leaving only the portion of the platform you actually use for your feet left and right intact.

While it will require some mods to the bodywork, I would add something like a top tube on a bicycle. That would greatly improve the strength of the frame...enough that you could even cut out some of the weight at the bottom of the original frame and still have a stronger frame than the original with less weight.

Thanks, yeah the issue is I'm using mid-mount motor instead of hub motor. So missing some space because of this.

Even with a hubmotor those kinds of scoots don't have much room for batteries. What I'm talking about is modifying the look toward something like the Derbi's that Scottydog uses for his escooters. That unused space along the center line offers lots of room for batteries. Check out his thread here https://endless-sphere.com/forums/viewtopic.php?f=12&t=59873.

I see now what you mean with the top tube from a bicycle, to make room in the bottom. Very good idea!

I think that would even give me room for 48 x LiFePO4 32650 with much better weight distribution.

 

[Balmorhea]

I’m not surprised that direct drive is better than CVT in your application, but I am curious what was so awful about CVT?

If you're interested in trying CVT's with electric motors, then check with forum member Gwhy.

I’m not interested in that. But I can imagine that an appropriate CVT would be useful for electric motors that have limited effective RPM ranges, like for instance a shunt wound DC motor or a synchronous AC motor. Whether there are any appropriate CVTs for light EVs, other than NuVinci/Enviolo hubs, I don’t know.

 

[kreal]

I’m not surprised that direct drive is better than CVT in your application, but I am curious what was so awful about CVT?

If you're interested in trying CVT's with electric motors, then check with forum member Gwhy.

I’m not interested in that. But I can imagine that an appropriate CVT would be useful for electric motors that have limited effective RPM ranges, like for instance a shunt wound DC motor or a synchronous AC motor. Whether there are any appropriate CVTs for light EVs, other than NuVinci/Enviolo hubs, I don’t know.

I did find this one, while searching for information:

 

[John in CR]

I’m not surprised that direct drive is better than CVT in your application, but I am curious what was so awful about CVT?

If you're interested in trying CVT's with electric motors, then check with forum member Gwhy.

I’m not interested in that. But I can imagine that an appropriate CVT would be useful for electric motors that have limited effective RPM ranges, like for instance a shunt wound DC motor or a synchronous AC motor. Whether there are any appropriate CVTs for light EVs, other than NuVinci/Enviolo hubs, I don’t know.

NuVinci = big losses and limited torque handling, so relatively low power limits.

There are a number of belt driven types like used on scooters. The Comet Torq-A-Verter is one and there are some with significantly higher power handling used on sand rails and other smoke belching machines. I have a torq-a-verter, which I put on the first lead laden beast I made, and I'd never go back to that nonsense, except maybe for some kind of off road vehicle where I truly needed lower gearing for some very low speed high load situations. Even then I'd prefer a fixed 2 speed for better efficiency and the ability to still have regen.

I have ebikes that will exceed 100mph (113mph is my top so far), and those can climb a 20% grade even with a passenger aboard as long as I don't go too slow where heat gets out of hand due to spikes in phase current with every change in throttle position due to low BEMF that acts as a buffer at higher rpm. That's using hubmotors without field weakening to extend rpm higher, so I can hardly agree that electric motors have "limited effective RPM ranges". That kind of comment applies to smokers not electrics, because ICE's have very limited torque bands compared to electric motors, which can produce maximum torque starting at 0rpm.

 

[Balmorhea]

I have ebikes that will exceed 100mph (113mph is my top so far), and those can climb a 20% grade even with a passenger aboard as long as I don't go too slow where heat gets out of hand due to spikes in phase current with every change in throttle position due to low BEMF that acts as a buffer at higher rpm. That's using hubmotors without field weakening to extend rpm higher, so I can hardly agree that electric motors have "limited effective RPM ranges".

I agree with you about brushless PMDC and even series wound DC motors, but that’s not all electric motors. I already identified a couple of kinds that work well within a narrow speed range, but poorly when pushed out of that range.

Shunt wound DC motors used to be somewhat common for electric car conversions, but they only make sense when using the car’s original transmission to get a relatively wide choice of gear ratio. Such a motor might be an economical choice for converting a former petroleum burning scooter like the one in this thread (but only if you keep the transmission).

NuVinci N171 was rated for 5kW, and had better than 80% efficiency in all ratios, so it was quite useful for light EVs when input torque could be kept within spec.

 

[John in CR]

NuVinci N171 was rated for 5kW, and had better than 80% efficiency in all ratios

Yes, and at best it was less than 90%, so you're talking about throwing away 10-20% right off the top when a chain drive when done correctly has less than 5% losses. Add in NuVinci's torque limitations and high price, and it's easy to understand why it never became a very successful product.

About 10 years ago someone shared a low loss design for a CVT that utilized 2 electric motors that was very interesting, but we never heard anything more. I wish I could find that info.

 

[kreal]

So I ended up using 3.2v 12Ah LiFePO4 pouch cells, works amazingly good, and plenty of room for them.




Also added active cooling for the controller and batteries, if it do any good I don't know, however it is pretty hot where I am.


[attachment=1]IMG_20200401_065703.jpg[/attachment

 

[kreal]

Added sidecar, with alot of batteries in box to carry heavy stuff using the 3000w QS motor.